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oasis-root

Compiled tree of Oasis Linux based on own branch at <https://hacktivis.me/git/oasis/> git clone https://anongit.hacktivis.me/git/oasis-root.git

ast.py (59572B)

    

  1. """
  2.     ast
  3.     ~~~
  5.     The `ast` module helps Python applications to process trees of the Python
  6.     abstract syntax grammar.  The abstract syntax itself might change with
  7.     each Python release; this module helps to find out programmatically what
  8.     the current grammar looks like and allows modifications of it.
  10.     An abstract syntax tree can be generated by passing `ast.PyCF_ONLY_AST` as
  11.     a flag to the `compile()` builtin function or by using the `parse()`
  12.     function from this module.  The result will be a tree of objects whose
  13.     classes all inherit from `ast.AST`.
  15.     A modified abstract syntax tree can be compiled into a Python code object
  16.     using the built-in `compile()` function.
  18.     Additionally various helper functions are provided that make working with
  19.     the trees simpler.  The main intention of the helper functions and this
  20.     module in general is to provide an easy to use interface for libraries
  21.     that work tightly with the python syntax (template engines for example).
  24.     :copyright: Copyright 2008 by Armin Ronacher.
  25.     :license: Python License.
  26. """
  27. import sys
  28. from _ast import *
  29. from contextlib import contextmanager, nullcontext
  30. from enum import IntEnum, auto
  33. def parse(source, filename='<unknown>', mode='exec', *,
  34.           type_comments=False, feature_version=None):
  35.     """
  36.     Parse the source into an AST node.
  37.     Equivalent to compile(source, filename, mode, PyCF_ONLY_AST).
  38.     Pass type_comments=True to get back type comments where the syntax allows.
  39.     """
  40.     flags = PyCF_ONLY_AST
  41.     if type_comments:
  42.         flags |= PyCF_TYPE_COMMENTS
  43.     if isinstance(feature_version, tuple):
  44.         major, minor = feature_version  # Should be a 2-tuple.
  45.         assert major == 3
  46.         feature_version = minor
  47.     elif feature_version is None:
  48.         feature_version = -1
  49.     # Else it should be an int giving the minor version for 3.x.
  50.     return compile(source, filename, mode, flags,
  51.                    _feature_version=feature_version)
  54. def literal_eval(node_or_string):
  55.     """
  56.     Safely evaluate an expression node or a string containing a Python
  57.     expression.  The string or node provided may only consist of the following
  58.     Python literal structures: strings, bytes, numbers, tuples, lists, dicts,
  59.     sets, booleans, and None.
  60.     """
  61.     if isinstance(node_or_string, str):
  62.         node_or_string = parse(node_or_string.lstrip(" \t"), mode='eval')
  63.     if isinstance(node_or_string, Expression):
  64.         node_or_string = node_or_string.body
  65.     def _raise_malformed_node(node):
  66.         msg = "malformed node or string"
  67.         if lno := getattr(node, 'lineno', None):
  68.             msg += f' on line {lno}'
  69.         raise ValueError(msg + f': {node!r}')
  70.     def _convert_num(node):
  71.         if not isinstance(node, Constant) or type(node.value) not in (int, float, complex):
  72.             _raise_malformed_node(node)
  73.         return node.value
  74.     def _convert_signed_num(node):
  75.         if isinstance(node, UnaryOp) and isinstance(node.op, (UAdd, USub)):
  76.             operand = _convert_num(node.operand)
  77.             if isinstance(node.op, UAdd):
  78.                 return + operand
  79.             else:
  80.                 return - operand
  81.         return _convert_num(node)
  82.     def _convert(node):
  83.         if isinstance(node, Constant):
  84.             return node.value
  85.         elif isinstance(node, Tuple):
  86.             return tuple(map(_convert, node.elts))
  87.         elif isinstance(node, List):
  88.             return list(map(_convert, node.elts))
  89.         elif isinstance(node, Set):
  90.             return set(map(_convert, node.elts))
  91.         elif (isinstance(node, Call) and isinstance(node.func, Name) and
  92.               node.func.id == 'set' and node.args == node.keywords == []):
  93.             return set()
  94.         elif isinstance(node, Dict):
  95.             if len(node.keys) != len(node.values):
  96.                 _raise_malformed_node(node)
  97.             return dict(zip(map(_convert, node.keys),
  98.                             map(_convert, node.values)))
  99.         elif isinstance(node, BinOp) and isinstance(node.op, (Add, Sub)):
  100.             left = _convert_signed_num(node.left)
  101.             right = _convert_num(node.right)
  102.             if isinstance(left, (int, float)) and isinstance(right, complex):
  103.                 if isinstance(node.op, Add):
  104.                     return left + right
  105.                 else:
  106.                     return left - right
  107.         return _convert_signed_num(node)
  108.     return _convert(node_or_string)
  111. def dump(node, annotate_fields=True, include_attributes=False, *, indent=None):
  112.     """
  113.     Return a formatted dump of the tree in node.  This is mainly useful for
  114.     debugging purposes.  If annotate_fields is true (by default),
  115.     the returned string will show the names and the values for fields.
  116.     If annotate_fields is false, the result string will be more compact by
  117.     omitting unambiguous field names.  Attributes such as line
  118.     numbers and column offsets are not dumped by default.  If this is wanted,
  119.     include_attributes can be set to true.  If indent is a non-negative
  120.     integer or string, then the tree will be pretty-printed with that indent
  121.     level. None (the default) selects the single line representation.
  122.     """
  123.     def _format(node, level=0):
  124.         if indent is not None:
  125.             level += 1
  126.             prefix = '\n' + indent * level
  127.             sep = ',\n' + indent * level
  128.         else:
  129.             prefix = ''
  130.             sep = ', '
  131.         if isinstance(node, AST):
  132.             cls = type(node)
  133.             args = []
  134.             allsimple = True
  135.             keywords = annotate_fields
  136.             for name in node._fields:
  137.                 try:
  138.                     value = getattr(node, name)
  139.                 except AttributeError:
  140.                     keywords = True
  141.                     continue
  142.                 if value is None and getattr(cls, name, ...) is None:
  143.                     keywords = True
  144.                     continue
  145.                 value, simple = _format(value, level)
  146.                 allsimple = allsimple and simple
  147.                 if keywords:
  148.                     args.append('%s=%s' % (name, value))
  149.                 else:
  150.                     args.append(value)
  151.             if include_attributes and node._attributes:
  152.                 for name in node._attributes:
  153.                     try:
  154.                         value = getattr(node, name)
  155.                     except AttributeError:
  156.                         continue
  157.                     if value is None and getattr(cls, name, ...) is None:
  158.                         continue
  159.                     value, simple = _format(value, level)
  160.                     allsimple = allsimple and simple
  161.                     args.append('%s=%s' % (name, value))
  162.             if allsimple and len(args) <= 3:
  163.                 return '%s(%s)' % (node.__class__.__name__, ', '.join(args)), not args
  164.             return '%s(%s%s)' % (node.__class__.__name__, prefix, sep.join(args)), False
  165.         elif isinstance(node, list):
  166.             if not node:
  167.                 return '[]', True
  168.             return '[%s%s]' % (prefix, sep.join(_format(x, level)[0] for x in node)), False
  169.         return repr(node), True
  171.     if not isinstance(node, AST):
  172.         raise TypeError('expected AST, got %r' % node.__class__.__name__)
  173.     if indent is not None and not isinstance(indent, str):
  174.         indent = ' ' * indent
  175.     return _format(node)[0]
  178. def copy_location(new_node, old_node):
  179.     """
  180.     Copy source location (`lineno`, `col_offset`, `end_lineno`, and `end_col_offset`
  181.     attributes) from *old_node* to *new_node* if possible, and return *new_node*.
  182.     """
  183.     for attr in 'lineno', 'col_offset', 'end_lineno', 'end_col_offset':
  184.         if attr in old_node._attributes and attr in new_node._attributes:
  185.             value = getattr(old_node, attr, None)
  186.             # end_lineno and end_col_offset are optional attributes, and they
  187.             # should be copied whether the value is None or not.
  188.             if value is not None or (
  189.                 hasattr(old_node, attr) and attr.startswith("end_")
  190.             ):
  191.                 setattr(new_node, attr, value)
  192.     return new_node
  195. def fix_missing_locations(node):
  196.     """
  197.     When you compile a node tree with compile(), the compiler expects lineno and
  198.     col_offset attributes for every node that supports them.  This is rather
  199.     tedious to fill in for generated nodes, so this helper adds these attributes
  200.     recursively where not already set, by setting them to the values of the
  201.     parent node.  It works recursively starting at *node*.
  202.     """
  203.     def _fix(node, lineno, col_offset, end_lineno, end_col_offset):
  204.         if 'lineno' in node._attributes:
  205.             if not hasattr(node, 'lineno'):
  206.                 node.lineno = lineno
  207.             else:
  208.                 lineno = node.lineno
  209.         if 'end_lineno' in node._attributes:
  210.             if getattr(node, 'end_lineno', None) is None:
  211.                 node.end_lineno = end_lineno
  212.             else:
  213.                 end_lineno = node.end_lineno
  214.         if 'col_offset' in node._attributes:
  215.             if not hasattr(node, 'col_offset'):
  216.                 node.col_offset = col_offset
  217.             else:
  218.                 col_offset = node.col_offset
  219.         if 'end_col_offset' in node._attributes:
  220.             if getattr(node, 'end_col_offset', None) is None:
  221.                 node.end_col_offset = end_col_offset
  222.             else:
  223.                 end_col_offset = node.end_col_offset
  224.         for child in iter_child_nodes(node):
  225.             _fix(child, lineno, col_offset, end_lineno, end_col_offset)
  226.     _fix(node, 1, 0, 1, 0)
  227.     return node
  230. def increment_lineno(node, n=1):
  231.     """
  232.     Increment the line number and end line number of each node in the tree
  233.     starting at *node* by *n*. This is useful to "move code" to a different
  234.     location in a file.
  235.     """
  236.     for child in walk(node):
  237.         if 'lineno' in child._attributes:
  238.             child.lineno = getattr(child, 'lineno', 0) + n
  239.         if (
  240.             "end_lineno" in child._attributes
  241.             and (end_lineno := getattr(child, "end_lineno", 0)) is not None
  242.         ):
  243.             child.end_lineno = end_lineno + n
  244.     return node
  247. def iter_fields(node):
  248.     """
  249.     Yield a tuple of ``(fieldname, value)`` for each field in ``node._fields``
  250.     that is present on *node*.
  251.     """
  252.     for field in node._fields:
  253.         try:
  254.             yield field, getattr(node, field)
  255.         except AttributeError:
  256.             pass
  259. def iter_child_nodes(node):
  260.     """
  261.     Yield all direct child nodes of *node*, that is, all fields that are nodes
  262.     and all items of fields that are lists of nodes.
  263.     """
  264.     for name, field in iter_fields(node):
  265.         if isinstance(field, AST):
  266.             yield field
  267.         elif isinstance(field, list):
  268.             for item in field:
  269.                 if isinstance(item, AST):
  270.                     yield item
  273. def get_docstring(node, clean=True):
  274.     """
  275.     Return the docstring for the given node or None if no docstring can
  276.     be found.  If the node provided does not have docstrings a TypeError
  277.     will be raised.
  279.     If *clean* is `True`, all tabs are expanded to spaces and any whitespace
  280.     that can be uniformly removed from the second line onwards is removed.
  281.     """
  282.     if not isinstance(node, (AsyncFunctionDef, FunctionDef, ClassDef, Module)):
  283.         raise TypeError("%r can't have docstrings" % node.__class__.__name__)
  284.     if not(node.body and isinstance(node.body[0], Expr)):
  285.         return None
  286.     node = node.body[0].value
  287.     if isinstance(node, Str):
  288.         text = node.s
  289.     elif isinstance(node, Constant) and isinstance(node.value, str):
  290.         text = node.value
  291.     else:
  292.         return None
  293.     if clean:
  294.         import inspect
  295.         text = inspect.cleandoc(text)
  296.     return text
  299. def _splitlines_no_ff(source):
  300.     """Split a string into lines ignoring form feed and other chars.
  302.     This mimics how the Python parser splits source code.
  303.     """
  304.     idx = 0
  305.     lines = []
  306.     next_line = ''
  307.     while idx < len(source):
  308.         c = source[idx]
  309.         next_line += c
  310.         idx += 1
  311.         # Keep \r\n together
  312.         if c == '\r' and idx < len(source) and source[idx] == '\n':
  313.             next_line += '\n'
  314.             idx += 1
  315.         if c in '\r\n':
  316.             lines.append(next_line)
  317.             next_line = ''
  319.     if next_line:
  320.         lines.append(next_line)
  321.     return lines
  324. def _pad_whitespace(source):
  325.     r"""Replace all chars except '\f\t' in a line with spaces."""
  326.     result = ''
  327.     for c in source:
  328.         if c in '\f\t':
  329.             result += c
  330.         else:
  331.             result += ' '
  332.     return result
  335. def get_source_segment(source, node, *, padded=False):
  336.     """Get source code segment of the *source* that generated *node*.
  338.     If some location information (`lineno`, `end_lineno`, `col_offset`,
  339.     or `end_col_offset`) is missing, return None.
  341.     If *padded* is `True`, the first line of a multi-line statement will
  342.     be padded with spaces to match its original position.
  343.     """
  344.     try:
  345.         if node.end_lineno is None or node.end_col_offset is None:
  346.             return None
  347.         lineno = node.lineno - 1
  348.         end_lineno = node.end_lineno - 1
  349.         col_offset = node.col_offset
  350.         end_col_offset = node.end_col_offset
  351.     except AttributeError:
  352.         return None
  354.     lines = _splitlines_no_ff(source)
  355.     if end_lineno == lineno:
  356.         return lines[lineno].encode()[col_offset:end_col_offset].decode()
  358.     if padded:
  359.         padding = _pad_whitespace(lines[lineno].encode()[:col_offset].decode())
  360.     else:
  361.         padding = ''
  363.     first = padding + lines[lineno].encode()[col_offset:].decode()
  364.     last = lines[end_lineno].encode()[:end_col_offset].decode()
  365.     lines = lines[lineno+1:end_lineno]
  367.     lines.insert(0, first)
  368.     lines.append(last)
  369.     return ''.join(lines)
  372. def walk(node):
  373.     """
  374.     Recursively yield all descendant nodes in the tree starting at *node*
  375.     (including *node* itself), in no specified order.  This is useful if you
  376.     only want to modify nodes in place and don't care about the context.
  377.     """
  378.     from collections import deque
  379.     todo = deque([node])
  380.     while todo:
  381.         node = todo.popleft()
  382.         todo.extend(iter_child_nodes(node))
  383.         yield node
  386. class NodeVisitor(object):
  387.     """
  388.     A node visitor base class that walks the abstract syntax tree and calls a
  389.     visitor function for every node found.  This function may return a value
  390.     which is forwarded by the `visit` method.
  392.     This class is meant to be subclassed, with the subclass adding visitor
  393.     methods.
  395.     Per default the visitor functions for the nodes are ``'visit_'`` +
  396.     class name of the node.  So a `TryFinally` node visit function would
  397.     be `visit_TryFinally`.  This behavior can be changed by overriding
  398.     the `visit` method.  If no visitor function exists for a node
  399.     (return value `None`) the `generic_visit` visitor is used instead.
  401.     Don't use the `NodeVisitor` if you want to apply changes to nodes during
  402.     traversing.  For this a special visitor exists (`NodeTransformer`) that
  403.     allows modifications.
  404.     """
  406.     def visit(self, node):
  407.         """Visit a node."""
  408.         method = 'visit_' + node.__class__.__name__
  409.         visitor = getattr(self, method, self.generic_visit)
  410.         return visitor(node)
  412.     def generic_visit(self, node):
  413.         """Called if no explicit visitor function exists for a node."""
  414.         for field, value in iter_fields(node):
  415.             if isinstance(value, list):
  416.                 for item in value:
  417.                     if isinstance(item, AST):
  418.                         self.visit(item)
  419.             elif isinstance(value, AST):
  420.                 self.visit(value)
  422.     def visit_Constant(self, node):
  423.         value = node.value
  424.         type_name = _const_node_type_names.get(type(value))
  425.         if type_name is None:
  426.             for cls, name in _const_node_type_names.items():
  427.                 if isinstance(value, cls):
  428.                     type_name = name
  429.                     break
  430.         if type_name is not None:
  431.             method = 'visit_' + type_name
  432.             try:
  433.                 visitor = getattr(self, method)
  434.             except AttributeError:
  435.                 pass
  436.             else:
  437.                 import warnings
  438.                 warnings.warn(f"{method} is deprecated; add visit_Constant",
  439.                               DeprecationWarning, 2)
  440.                 return visitor(node)
  441.         return self.generic_visit(node)
  444. class NodeTransformer(NodeVisitor):
  445.     """
  446.     A :class:`NodeVisitor` subclass that walks the abstract syntax tree and
  447.     allows modification of nodes.
  449.     The `NodeTransformer` will walk the AST and use the return value of the
  450.     visitor methods to replace or remove the old node.  If the return value of
  451.     the visitor method is ``None``, the node will be removed from its location,
  452.     otherwise it is replaced with the return value.  The return value may be the
  453.     original node in which case no replacement takes place.
  455.     Here is an example transformer that rewrites all occurrences of name lookups
  456.     (``foo``) to ``data['foo']``::
  458.        class RewriteName(NodeTransformer):
  460.            def visit_Name(self, node):
  461.                return Subscript(
  462.                    value=Name(id='data', ctx=Load()),
  463.                    slice=Constant(value=node.id),
  464.                    ctx=node.ctx
  465.                )
  467.     Keep in mind that if the node you're operating on has child nodes you must
  468.     either transform the child nodes yourself or call the :meth:`generic_visit`
  469.     method for the node first.
  471.     For nodes that were part of a collection of statements (that applies to all
  472.     statement nodes), the visitor may also return a list of nodes rather than
  473.     just a single node.
  475.     Usually you use the transformer like this::
  477.        node = YourTransformer().visit(node)
  478.     """
  480.     def generic_visit(self, node):
  481.         for field, old_value in iter_fields(node):
  482.             if isinstance(old_value, list):
  483.                 new_values = []
  484.                 for value in old_value:
  485.                     if isinstance(value, AST):
  486.                         value = self.visit(value)
  487.                         if value is None:
  488.                             continue
  489.                         elif not isinstance(value, AST):
  490.                             new_values.extend(value)
  491.                             continue
  492.                     new_values.append(value)
  493.                 old_value[:] = new_values
  494.             elif isinstance(old_value, AST):
  495.                 new_node = self.visit(old_value)
  496.                 if new_node is None:
  497.                     delattr(node, field)
  498.                 else:
  499.                     setattr(node, field, new_node)
  500.         return node
  503. # If the ast module is loaded more than once, only add deprecated methods once
  504. if not hasattr(Constant, 'n'):
  505.     # The following code is for backward compatibility.
  506.     # It will be removed in future.
  508.     def _getter(self):
  509.         """Deprecated. Use value instead."""
  510.         return self.value
  512.     def _setter(self, value):
  513.         self.value = value
  515.     Constant.n = property(_getter, _setter)
  516.     Constant.s = property(_getter, _setter)
  518. class _ABC(type):
  520.     def __init__(cls, *args):
  521.         cls.__doc__ = """Deprecated AST node class. Use ast.Constant instead"""
  523.     def __instancecheck__(cls, inst):
  524.         if not isinstance(inst, Constant):
  525.             return False
  526.         if cls in _const_types:
  527.             try:
  528.                 value = inst.value
  529.             except AttributeError:
  530.                 return False
  531.             else:
  532.                 return (
  533.                     isinstance(value, _const_types[cls]) and
  534.                     not isinstance(value, _const_types_not.get(cls, ()))
  535.                 )
  536.         return type.__instancecheck__(cls, inst)
  538. def _new(cls, *args, **kwargs):
  539.     for key in kwargs:
  540.         if key not in cls._fields:
  541.             # arbitrary keyword arguments are accepted
  542.             continue
  543.         pos = cls._fields.index(key)
  544.         if pos < len(args):
  545.             raise TypeError(f"{cls.__name__} got multiple values for argument {key!r}")
  546.     if cls in _const_types:
  547.         return Constant(*args, **kwargs)
  548.     return Constant.__new__(cls, *args, **kwargs)
  550. class Num(Constant, metaclass=_ABC):
  551.     _fields = ('n',)
  552.     __new__ = _new
  554. class Str(Constant, metaclass=_ABC):
  555.     _fields = ('s',)
  556.     __new__ = _new
  558. class Bytes(Constant, metaclass=_ABC):
  559.     _fields = ('s',)
  560.     __new__ = _new
  562. class NameConstant(Constant, metaclass=_ABC):
  563.     __new__ = _new
  565. class Ellipsis(Constant, metaclass=_ABC):
  566.     _fields = ()
  568.     def __new__(cls, *args, **kwargs):
  569.         if cls is Ellipsis:
  570.             return Constant(..., *args, **kwargs)
  571.         return Constant.__new__(cls, *args, **kwargs)
  573. _const_types = {
  574.     Num: (int, float, complex),
  575.     Str: (str,),
  576.     Bytes: (bytes,),
  577.     NameConstant: (type(None), bool),
  578.     Ellipsis: (type(...),),
  579. }
  580. _const_types_not = {
  581.     Num: (bool,),
  582. }
  584. _const_node_type_names = {
  585.     bool: 'NameConstant',  # should be before int
  586.     type(None): 'NameConstant',
  587.     int: 'Num',
  588.     float: 'Num',
  589.     complex: 'Num',
  590.     str: 'Str',
  591.     bytes: 'Bytes',
  592.     type(...): 'Ellipsis',
  593. }
  595. class slice(AST):
  596.     """Deprecated AST node class."""
  598. class Index(slice):
  599.     """Deprecated AST node class. Use the index value directly instead."""
  600.     def __new__(cls, value, **kwargs):
  601.         return value
  603. class ExtSlice(slice):
  604.     """Deprecated AST node class. Use ast.Tuple instead."""
  605.     def __new__(cls, dims=(), **kwargs):
  606.         return Tuple(list(dims), Load(), **kwargs)
  608. # If the ast module is loaded more than once, only add deprecated methods once
  609. if not hasattr(Tuple, 'dims'):
  610.     # The following code is for backward compatibility.
  611.     # It will be removed in future.
  613.     def _dims_getter(self):
  614.         """Deprecated. Use elts instead."""
  615.         return self.elts
  617.     def _dims_setter(self, value):
  618.         self.elts = value
  620.     Tuple.dims = property(_dims_getter, _dims_setter)
  622. class Suite(mod):
  623.     """Deprecated AST node class.  Unused in Python 3."""
  625. class AugLoad(expr_context):
  626.     """Deprecated AST node class.  Unused in Python 3."""
  628. class AugStore(expr_context):
  629.     """Deprecated AST node class.  Unused in Python 3."""
  631. class Param(expr_context):
  632.     """Deprecated AST node class.  Unused in Python 3."""
  635. # Large float and imaginary literals get turned into infinities in the AST.
  636. # We unparse those infinities to INFSTR.
  637. _INFSTR = "1e" + repr(sys.float_info.max_10_exp + 1)
  639. class _Precedence(IntEnum):
  640.     """Precedence table that originated from python grammar."""
  642.     TUPLE = auto()
  643.     YIELD = auto()           # 'yield', 'yield from'
  644.     TEST = auto()            # 'if'-'else', 'lambda'
  645.     OR = auto()              # 'or'
  646.     AND = auto()             # 'and'
  647.     NOT = auto()             # 'not'
  648.     CMP = auto()             # '<', '>', '==', '>=', '<=', '!=',
  649.                              # 'in', 'not in', 'is', 'is not'
  650.     EXPR = auto()
  651.     BOR = EXPR               # '|'
  652.     BXOR = auto()            # '^'
  653.     BAND = auto()            # '&'
  654.     SHIFT = auto()           # '<<', '>>'
  655.     ARITH = auto()           # '+', '-'
  656.     TERM = auto()            # '*', '@', '/', '%', '//'
  657.     FACTOR = auto()          # unary '+', '-', '~'
  658.     POWER = auto()           # '**'
  659.     AWAIT = auto()           # 'await'
  660.     ATOM = auto()
  662.     def next(self):
  663.         try:
  664.             return self.__class__(self + 1)
  665.         except ValueError:
  666.             return self
  669. _SINGLE_QUOTES = ("'", '"')
  670. _MULTI_QUOTES = ('"""', "'''")
  671. _ALL_QUOTES = (*_SINGLE_QUOTES, *_MULTI_QUOTES)
  673. class _Unparser(NodeVisitor):
  674.     """Methods in this class recursively traverse an AST and
  675.     output source code for the abstract syntax; original formatting
  676.     is disregarded."""
  678.     def __init__(self, *, _avoid_backslashes=False):
  679.         self._source = []
  680.         self._buffer = []
  681.         self._precedences = {}
  682.         self._type_ignores = {}
  683.         self._indent = 0
  684.         self._avoid_backslashes = _avoid_backslashes
  686.     def interleave(self, inter, f, seq):
  687.         """Call f on each item in seq, calling inter() in between."""
  688.         seq = iter(seq)
  689.         try:
  690.             f(next(seq))
  691.         except StopIteration:
  692.             pass
  693.         else:
  694.             for x in seq:
  695.                 inter()
  696.                 f(x)
  698.     def items_view(self, traverser, items):
  699.         """Traverse and separate the given *items* with a comma and append it to
  700.         the buffer. If *items* is a single item sequence, a trailing comma
  701.         will be added."""
  702.         if len(items) == 1:
  703.             traverser(items[0])
  704.             self.write(",")
  705.         else:
  706.             self.interleave(lambda: self.write(", "), traverser, items)
  708.     def maybe_newline(self):
  709.         """Adds a newline if it isn't the start of generated source"""
  710.         if self._source:
  711.             self.write("\n")
  713.     def fill(self, text=""):
  714.         """Indent a piece of text and append it, according to the current
  715.         indentation level"""
  716.         self.maybe_newline()
  717.         self.write("    " * self._indent + text)
  719.     def write(self, text):
  720.         """Append a piece of text"""
  721.         self._source.append(text)
  723.     def buffer_writer(self, text):
  724.         self._buffer.append(text)
  726.     @property
  727.     def buffer(self):
  728.         value = "".join(self._buffer)
  729.         self._buffer.clear()
  730.         return value
  732.     @contextmanager
  733.     def block(self, *, extra = None):
  734.         """A context manager for preparing the source for blocks. It adds
  735.         the character':', increases the indentation on enter and decreases
  736.         the indentation on exit. If *extra* is given, it will be directly
  737.         appended after the colon character.
  738.         """
  739.         self.write(":")
  740.         if extra:
  741.             self.write(extra)
  742.         self._indent += 1
  743.         yield
  744.         self._indent -= 1
  746.     @contextmanager
  747.     def delimit(self, start, end):
  748.         """A context manager for preparing the source for expressions. It adds
  749.         *start* to the buffer and enters, after exit it adds *end*."""
  751.         self.write(start)
  752.         yield
  753.         self.write(end)
  755.     def delimit_if(self, start, end, condition):
  756.         if condition:
  757.             return self.delimit(start, end)
  758.         else:
  759.             return nullcontext()
  761.     def require_parens(self, precedence, node):
  762.         """Shortcut to adding precedence related parens"""
  763.         return self.delimit_if("(", ")", self.get_precedence(node) > precedence)
  765.     def get_precedence(self, node):
  766.         return self._precedences.get(node, _Precedence.TEST)
  768.     def set_precedence(self, precedence, *nodes):
  769.         for node in nodes:
  770.             self._precedences[node] = precedence
  772.     def get_raw_docstring(self, node):
  773.         """If a docstring node is found in the body of the *node* parameter,
  774.         return that docstring node, None otherwise.
  776.         Logic mirrored from ``_PyAST_GetDocString``."""
  777.         if not isinstance(
  778.             node, (AsyncFunctionDef, FunctionDef, ClassDef, Module)
  779.         ) or len(node.body) < 1:
  780.             return None
  781.         node = node.body[0]
  782.         if not isinstance(node, Expr):
  783.             return None
  784.         node = node.value
  785.         if isinstance(node, Constant) and isinstance(node.value, str):
  786.             return node
  788.     def get_type_comment(self, node):
  789.         comment = self._type_ignores.get(node.lineno) or node.type_comment
  790.         if comment is not None:
  791.             return f" # type: {comment}"
  793.     def traverse(self, node):
  794.         if isinstance(node, list):
  795.             for item in node:
  796.                 self.traverse(item)
  797.         else:
  798.             super().visit(node)
  800.     # Note: as visit() resets the output text, do NOT rely on
  801.     # NodeVisitor.generic_visit to handle any nodes (as it calls back in to
  802.     # the subclass visit() method, which resets self._source to an empty list)
  803.     def visit(self, node):
  804.         """Outputs a source code string that, if converted back to an ast
  805.         (using ast.parse) will generate an AST equivalent to *node*"""
  806.         self._source = []
  807.         self.traverse(node)
  808.         return "".join(self._source)
  810.     def _write_docstring_and_traverse_body(self, node):
  811.         if (docstring := self.get_raw_docstring(node)):
  812.             self._write_docstring(docstring)
  813.             self.traverse(node.body[1:])
  814.         else:
  815.             self.traverse(node.body)
  817.     def visit_Module(self, node):
  818.         self._type_ignores = {
  819.             ignore.lineno: f"ignore{ignore.tag}"
  820.             for ignore in node.type_ignores
  821.         }
  822.         self._write_docstring_and_traverse_body(node)
  823.         self._type_ignores.clear()
  825.     def visit_FunctionType(self, node):
  826.         with self.delimit("(", ")"):
  827.             self.interleave(
  828.                 lambda: self.write(", "), self.traverse, node.argtypes
  829.             )
  831.         self.write(" -> ")
  832.         self.traverse(node.returns)
  834.     def visit_Expr(self, node):
  835.         self.fill()
  836.         self.set_precedence(_Precedence.YIELD, node.value)
  837.         self.traverse(node.value)
  839.     def visit_NamedExpr(self, node):
  840.         with self.require_parens(_Precedence.TUPLE, node):
  841.             self.set_precedence(_Precedence.ATOM, node.target, node.value)
  842.             self.traverse(node.target)
  843.             self.write(" := ")
  844.             self.traverse(node.value)
  846.     def visit_Import(self, node):
  847.         self.fill("import ")
  848.         self.interleave(lambda: self.write(", "), self.traverse, node.names)
  850.     def visit_ImportFrom(self, node):
  851.         self.fill("from ")
  852.         self.write("." * node.level)
  853.         if node.module:
  854.             self.write(node.module)
  855.         self.write(" import ")
  856.         self.interleave(lambda: self.write(", "), self.traverse, node.names)
  858.     def visit_Assign(self, node):
  859.         self.fill()
  860.         for target in node.targets:
  861.             self.traverse(target)
  862.             self.write(" = ")
  863.         self.traverse(node.value)
  864.         if type_comment := self.get_type_comment(node):
  865.             self.write(type_comment)
  867.     def visit_AugAssign(self, node):
  868.         self.fill()
  869.         self.traverse(node.target)
  870.         self.write(" " + self.binop[node.op.__class__.__name__] + "= ")
  871.         self.traverse(node.value)
  873.     def visit_AnnAssign(self, node):
  874.         self.fill()
  875.         with self.delimit_if("(", ")", not node.simple and isinstance(node.target, Name)):
  876.             self.traverse(node.target)
  877.         self.write(": ")
  878.         self.traverse(node.annotation)
  879.         if node.value:
  880.             self.write(" = ")
  881.             self.traverse(node.value)
  883.     def visit_Return(self, node):
  884.         self.fill("return")
  885.         if node.value:
  886.             self.write(" ")
  887.             self.traverse(node.value)
  889.     def visit_Pass(self, node):
  890.         self.fill("pass")
  892.     def visit_Break(self, node):
  893.         self.fill("break")
  895.     def visit_Continue(self, node):
  896.         self.fill("continue")
  898.     def visit_Delete(self, node):
  899.         self.fill("del ")
  900.         self.interleave(lambda: self.write(", "), self.traverse, node.targets)
  902.     def visit_Assert(self, node):
  903.         self.fill("assert ")
  904.         self.traverse(node.test)
  905.         if node.msg:
  906.             self.write(", ")
  907.             self.traverse(node.msg)
  909.     def visit_Global(self, node):
  910.         self.fill("global ")
  911.         self.interleave(lambda: self.write(", "), self.write, node.names)
  913.     def visit_Nonlocal(self, node):
  914.         self.fill("nonlocal ")
  915.         self.interleave(lambda: self.write(", "), self.write, node.names)
  917.     def visit_Await(self, node):
  918.         with self.require_parens(_Precedence.AWAIT, node):
  919.             self.write("await")
  920.             if node.value:
  921.                 self.write(" ")
  922.                 self.set_precedence(_Precedence.ATOM, node.value)
  923.                 self.traverse(node.value)
  925.     def visit_Yield(self, node):
  926.         with self.require_parens(_Precedence.YIELD, node):
  927.             self.write("yield")
  928.             if node.value:
  929.                 self.write(" ")
  930.                 self.set_precedence(_Precedence.ATOM, node.value)
  931.                 self.traverse(node.value)
  933.     def visit_YieldFrom(self, node):
  934.         with self.require_parens(_Precedence.YIELD, node):
  935.             self.write("yield from ")
  936.             if not node.value:
  937.                 raise ValueError("Node can't be used without a value attribute.")
  938.             self.set_precedence(_Precedence.ATOM, node.value)
  939.             self.traverse(node.value)
  941.     def visit_Raise(self, node):
  942.         self.fill("raise")
  943.         if not node.exc:
  944.             if node.cause:
  945.                 raise ValueError(f"Node can't use cause without an exception.")
  946.             return
  947.         self.write(" ")
  948.         self.traverse(node.exc)
  949.         if node.cause:
  950.             self.write(" from ")
  951.             self.traverse(node.cause)
  953.     def visit_Try(self, node):
  954.         self.fill("try")
  955.         with self.block():
  956.             self.traverse(node.body)
  957.         for ex in node.handlers:
  958.             self.traverse(ex)
  959.         if node.orelse:
  960.             self.fill("else")
  961.             with self.block():
  962.                 self.traverse(node.orelse)
  963.         if node.finalbody:
  964.             self.fill("finally")
  965.             with self.block():
  966.                 self.traverse(node.finalbody)
  968.     def visit_ExceptHandler(self, node):
  969.         self.fill("except")
  970.         if node.type:
  971.             self.write(" ")
  972.             self.traverse(node.type)
  973.         if node.name:
  974.             self.write(" as ")
  975.             self.write(node.name)
  976.         with self.block():
  977.             self.traverse(node.body)
  979.     def visit_ClassDef(self, node):
  980.         self.maybe_newline()
  981.         for deco in node.decorator_list:
  982.             self.fill("@")
  983.             self.traverse(deco)
  984.         self.fill("class " + node.name)
  985.         with self.delimit_if("(", ")", condition = node.bases or node.keywords):
  986.             comma = False
  987.             for e in node.bases:
  988.                 if comma:
  989.                     self.write(", ")
  990.                 else:
  991.                     comma = True
  992.                 self.traverse(e)
  993.             for e in node.keywords:
  994.                 if comma:
  995.                     self.write(", ")
  996.                 else:
  997.                     comma = True
  998.                 self.traverse(e)
  1000.         with self.block():
  1001.             self._write_docstring_and_traverse_body(node)
  1003.     def visit_FunctionDef(self, node):
  1004.         self._function_helper(node, "def")
  1006.     def visit_AsyncFunctionDef(self, node):
  1007.         self._function_helper(node, "async def")
  1009.     def _function_helper(self, node, fill_suffix):
  1010.         self.maybe_newline()
  1011.         for deco in node.decorator_list:
  1012.             self.fill("@")
  1013.             self.traverse(deco)
  1014.         def_str = fill_suffix + " " + node.name
  1015.         self.fill(def_str)
  1016.         with self.delimit("(", ")"):
  1017.             self.traverse(node.args)
  1018.         if node.returns:
  1019.             self.write(" -> ")
  1020.             self.traverse(node.returns)
  1021.         with self.block(extra=self.get_type_comment(node)):
  1022.             self._write_docstring_and_traverse_body(node)
  1024.     def visit_For(self, node):
  1025.         self._for_helper("for ", node)
  1027.     def visit_AsyncFor(self, node):
  1028.         self._for_helper("async for ", node)
  1030.     def _for_helper(self, fill, node):
  1031.         self.fill(fill)
  1032.         self.traverse(node.target)
  1033.         self.write(" in ")
  1034.         self.traverse(node.iter)
  1035.         with self.block(extra=self.get_type_comment(node)):
  1036.             self.traverse(node.body)
  1037.         if node.orelse:
  1038.             self.fill("else")
  1039.             with self.block():
  1040.                 self.traverse(node.orelse)
  1042.     def visit_If(self, node):
  1043.         self.fill("if ")
  1044.         self.traverse(node.test)
  1045.         with self.block():
  1046.             self.traverse(node.body)
  1047.         # collapse nested ifs into equivalent elifs.
  1048.         while node.orelse and len(node.orelse) == 1 and isinstance(node.orelse[0], If):
  1049.             node = node.orelse[0]
  1050.             self.fill("elif ")
  1051.             self.traverse(node.test)
  1052.             with self.block():
  1053.                 self.traverse(node.body)
  1054.         # final else
  1055.         if node.orelse:
  1056.             self.fill("else")
  1057.             with self.block():
  1058.                 self.traverse(node.orelse)
  1060.     def visit_While(self, node):
  1061.         self.fill("while ")
  1062.         self.traverse(node.test)
  1063.         with self.block():
  1064.             self.traverse(node.body)
  1065.         if node.orelse:
  1066.             self.fill("else")
  1067.             with self.block():
  1068.                 self.traverse(node.orelse)
  1070.     def visit_With(self, node):
  1071.         self.fill("with ")
  1072.         self.interleave(lambda: self.write(", "), self.traverse, node.items)
  1073.         with self.block(extra=self.get_type_comment(node)):
  1074.             self.traverse(node.body)
  1076.     def visit_AsyncWith(self, node):
  1077.         self.fill("async with ")
  1078.         self.interleave(lambda: self.write(", "), self.traverse, node.items)
  1079.         with self.block(extra=self.get_type_comment(node)):
  1080.             self.traverse(node.body)
  1082.     def _str_literal_helper(
  1083.         self, string, *, quote_types=_ALL_QUOTES, escape_special_whitespace=False
  1084.     ):
  1085.         """Helper for writing string literals, minimizing escapes.
  1086.         Returns the tuple (string literal to write, possible quote types).
  1087.         """
  1088.         def escape_char(c):
  1089.             # \n and \t are non-printable, but we only escape them if
  1090.             # escape_special_whitespace is True
  1091.             if not escape_special_whitespace and c in "\n\t":
  1092.                 return c
  1093.             # Always escape backslashes and other non-printable characters
  1094.             if c == "\\" or not c.isprintable():
  1095.                 return c.encode("unicode_escape").decode("ascii")
  1096.             return c
  1098.         escaped_string = "".join(map(escape_char, string))
  1099.         possible_quotes = quote_types
  1100.         if "\n" in escaped_string:
  1101.             possible_quotes = [q for q in possible_quotes if q in _MULTI_QUOTES]
  1102.         possible_quotes = [q for q in possible_quotes if q not in escaped_string]
  1103.         if not possible_quotes:
  1104.             # If there aren't any possible_quotes, fallback to using repr
  1105.             # on the original string. Try to use a quote from quote_types,
  1106.             # e.g., so that we use triple quotes for docstrings.
  1107.             string = repr(string)
  1108.             quote = next((q for q in quote_types if string[0] in q), string[0])
  1109.             return string[1:-1], [quote]
  1110.         if escaped_string:
  1111.             # Sort so that we prefer '''"''' over """\""""
  1112.             possible_quotes.sort(key=lambda q: q[0] == escaped_string[-1])
  1113.             # If we're using triple quotes and we'd need to escape a final
  1114.             # quote, escape it
  1115.             if possible_quotes[0][0] == escaped_string[-1]:
  1116.                 assert len(possible_quotes[0]) == 3
  1117.                 escaped_string = escaped_string[:-1] + "\\" + escaped_string[-1]
  1118.         return escaped_string, possible_quotes
  1120.     def _write_str_avoiding_backslashes(self, string, *, quote_types=_ALL_QUOTES):
  1121.         """Write string literal value with a best effort attempt to avoid backslashes."""
  1122.         string, quote_types = self._str_literal_helper(string, quote_types=quote_types)
  1123.         quote_type = quote_types[0]
  1124.         self.write(f"{quote_type}{string}{quote_type}")
  1126.     def visit_JoinedStr(self, node):
  1127.         self.write("f")
  1128.         if self._avoid_backslashes:
  1129.             self._fstring_JoinedStr(node, self.buffer_writer)
  1130.             self._write_str_avoiding_backslashes(self.buffer)
  1131.             return
  1133.         # If we don't need to avoid backslashes globally (i.e., we only need
  1134.         # to avoid them inside FormattedValues), it's cosmetically preferred
  1135.         # to use escaped whitespace. That is, it's preferred to use backslashes
  1136.         # for cases like: f"{x}\n". To accomplish this, we keep track of what
  1137.         # in our buffer corresponds to FormattedValues and what corresponds to
  1138.         # Constant parts of the f-string, and allow escapes accordingly.
  1139.         buffer = []
  1140.         for value in node.values:
  1141.             meth = getattr(self, "_fstring_" + type(value).__name__)
  1142.             meth(value, self.buffer_writer)
  1143.             buffer.append((self.buffer, isinstance(value, Constant)))
  1144.         new_buffer = []
  1145.         quote_types = _ALL_QUOTES
  1146.         for value, is_constant in buffer:
  1147.             # Repeatedly narrow down the list of possible quote_types
  1148.             value, quote_types = self._str_literal_helper(
  1149.                 value, quote_types=quote_types,
  1150.                 escape_special_whitespace=is_constant
  1151.             )
  1152.             new_buffer.append(value)
  1153.         value = "".join(new_buffer)
  1154.         quote_type = quote_types[0]
  1155.         self.write(f"{quote_type}{value}{quote_type}")
  1157.     def visit_FormattedValue(self, node):
  1158.         self.write("f")
  1159.         self._fstring_FormattedValue(node, self.buffer_writer)
  1160.         self._write_str_avoiding_backslashes(self.buffer)
  1162.     def _fstring_JoinedStr(self, node, write):
  1163.         for value in node.values:
  1164.             meth = getattr(self, "_fstring_" + type(value).__name__)
  1165.             meth(value, write)
  1167.     def _fstring_Constant(self, node, write):
  1168.         if not isinstance(node.value, str):
  1169.             raise ValueError("Constants inside JoinedStr should be a string.")
  1170.         value = node.value.replace("{", "{{").replace("}", "}}")
  1171.         write(value)
  1173.     def _fstring_FormattedValue(self, node, write):
  1174.         write("{")
  1175.         unparser = type(self)(_avoid_backslashes=True)
  1176.         unparser.set_precedence(_Precedence.TEST.next(), node.value)
  1177.         expr = unparser.visit(node.value)
  1178.         if expr.startswith("{"):
  1179.             write(" ")  # Separate pair of opening brackets as "{ {"
  1180.         if "\\" in expr:
  1181.             raise ValueError("Unable to avoid backslash in f-string expression part")
  1182.         write(expr)
  1183.         if node.conversion != -1:
  1184.             conversion = chr(node.conversion)
  1185.             if conversion not in "sra":
  1186.                 raise ValueError("Unknown f-string conversion.")
  1187.             write(f"!{conversion}")
  1188.         if node.format_spec:
  1189.             write(":")
  1190.             meth = getattr(self, "_fstring_" + type(node.format_spec).__name__)
  1191.             meth(node.format_spec, write)
  1192.         write("}")
  1194.     def visit_Name(self, node):
  1195.         self.write(node.id)
  1197.     def _write_docstring(self, node):
  1198.         self.fill()
  1199.         if node.kind == "u":
  1200.             self.write("u")
  1201.         self._write_str_avoiding_backslashes(node.value, quote_types=_MULTI_QUOTES)
  1203.     def _write_constant(self, value):
  1204.         if isinstance(value, (float, complex)):
  1205.             # Substitute overflowing decimal literal for AST infinities,
  1206.             # and inf - inf for NaNs.
  1207.             self.write(
  1208.                 repr(value)
  1209.                 .replace("inf", _INFSTR)
  1210.                 .replace("nan", f"({_INFSTR}-{_INFSTR})")
  1211.             )
  1212.         elif self._avoid_backslashes and isinstance(value, str):
  1213.             self._write_str_avoiding_backslashes(value)
  1214.         else:
  1215.             self.write(repr(value))
  1217.     def visit_Constant(self, node):
  1218.         value = node.value
  1219.         if isinstance(value, tuple):
  1220.             with self.delimit("(", ")"):
  1221.                 self.items_view(self._write_constant, value)
  1222.         elif value is ...:
  1223.             self.write("...")
  1224.         else:
  1225.             if node.kind == "u":
  1226.                 self.write("u")
  1227.             self._write_constant(node.value)
  1229.     def visit_List(self, node):
  1230.         with self.delimit("[", "]"):
  1231.             self.interleave(lambda: self.write(", "), self.traverse, node.elts)
  1233.     def visit_ListComp(self, node):
  1234.         with self.delimit("[", "]"):
  1235.             self.traverse(node.elt)
  1236.             for gen in node.generators:
  1237.                 self.traverse(gen)
  1239.     def visit_GeneratorExp(self, node):
  1240.         with self.delimit("(", ")"):
  1241.             self.traverse(node.elt)
  1242.             for gen in node.generators:
  1243.                 self.traverse(gen)
  1245.     def visit_SetComp(self, node):
  1246.         with self.delimit("{", "}"):
  1247.             self.traverse(node.elt)
  1248.             for gen in node.generators:
  1249.                 self.traverse(gen)
  1251.     def visit_DictComp(self, node):
  1252.         with self.delimit("{", "}"):
  1253.             self.traverse(node.key)
  1254.             self.write(": ")
  1255.             self.traverse(node.value)
  1256.             for gen in node.generators:
  1257.                 self.traverse(gen)
  1259.     def visit_comprehension(self, node):
  1260.         if node.is_async:
  1261.             self.write(" async for ")
  1262.         else:
  1263.             self.write(" for ")
  1264.         self.set_precedence(_Precedence.TUPLE, node.target)
  1265.         self.traverse(node.target)
  1266.         self.write(" in ")
  1267.         self.set_precedence(_Precedence.TEST.next(), node.iter, *node.ifs)
  1268.         self.traverse(node.iter)
  1269.         for if_clause in node.ifs:
  1270.             self.write(" if ")
  1271.             self.traverse(if_clause)
  1273.     def visit_IfExp(self, node):
  1274.         with self.require_parens(_Precedence.TEST, node):
  1275.             self.set_precedence(_Precedence.TEST.next(), node.body, node.test)
  1276.             self.traverse(node.body)
  1277.             self.write(" if ")
  1278.             self.traverse(node.test)
  1279.             self.write(" else ")
  1280.             self.set_precedence(_Precedence.TEST, node.orelse)
  1281.             self.traverse(node.orelse)
  1283.     def visit_Set(self, node):
  1284.         if node.elts:
  1285.             with self.delimit("{", "}"):
  1286.                 self.interleave(lambda: self.write(", "), self.traverse, node.elts)
  1287.         else:
  1288.             # `{}` would be interpreted as a dictionary literal, and
  1289.             # `set` might be shadowed. Thus:
  1290.             self.write('{*()}')
  1292.     def visit_Dict(self, node):
  1293.         def write_key_value_pair(k, v):
  1294.             self.traverse(k)
  1295.             self.write(": ")
  1296.             self.traverse(v)
  1298.         def write_item(item):
  1299.             k, v = item
  1300.             if k is None:
  1301.                 # for dictionary unpacking operator in dicts {**{'y': 2}}
  1302.                 # see PEP 448 for details
  1303.                 self.write("**")
  1304.                 self.set_precedence(_Precedence.EXPR, v)
  1305.                 self.traverse(v)
  1306.             else:
  1307.                 write_key_value_pair(k, v)
  1309.         with self.delimit("{", "}"):
  1310.             self.interleave(
  1311.                 lambda: self.write(", "), write_item, zip(node.keys, node.values)
  1312.             )
  1314.     def visit_Tuple(self, node):
  1315.         with self.delimit("(", ")"):
  1316.             self.items_view(self.traverse, node.elts)
  1318.     unop = {"Invert": "~", "Not": "not", "UAdd": "+", "USub": "-"}
  1319.     unop_precedence = {
  1320.         "not": _Precedence.NOT,
  1321.         "~": _Precedence.FACTOR,
  1322.         "+": _Precedence.FACTOR,
  1323.         "-": _Precedence.FACTOR,
  1324.     }
  1326.     def visit_UnaryOp(self, node):
  1327.         operator = self.unop[node.op.__class__.__name__]
  1328.         operator_precedence = self.unop_precedence[operator]
  1329.         with self.require_parens(operator_precedence, node):
  1330.             self.write(operator)
  1331.             # factor prefixes (+, -, ~) shouldn't be seperated
  1332.             # from the value they belong, (e.g: +1 instead of + 1)
  1333.             if operator_precedence is not _Precedence.FACTOR:
  1334.                 self.write(" ")
  1335.             self.set_precedence(operator_precedence, node.operand)
  1336.             self.traverse(node.operand)
  1338.     binop = {
  1339.         "Add": "+",
  1340.         "Sub": "-",
  1341.         "Mult": "*",
  1342.         "MatMult": "@",
  1343.         "Div": "/",
  1344.         "Mod": "%",
  1345.         "LShift": "<<",
  1346.         "RShift": ">>",
  1347.         "BitOr": "|",
  1348.         "BitXor": "^",
  1349.         "BitAnd": "&",
  1350.         "FloorDiv": "//",
  1351.         "Pow": "**",
  1352.     }
  1354.     binop_precedence = {
  1355.         "+": _Precedence.ARITH,
  1356.         "-": _Precedence.ARITH,
  1357.         "*": _Precedence.TERM,
  1358.         "@": _Precedence.TERM,
  1359.         "/": _Precedence.TERM,
  1360.         "%": _Precedence.TERM,
  1361.         "<<": _Precedence.SHIFT,
  1362.         ">>": _Precedence.SHIFT,
  1363.         "|": _Precedence.BOR,
  1364.         "^": _Precedence.BXOR,
  1365.         "&": _Precedence.BAND,
  1366.         "//": _Precedence.TERM,
  1367.         "**": _Precedence.POWER,
  1368.     }
  1370.     binop_rassoc = frozenset(("**",))
  1371.     def visit_BinOp(self, node):
  1372.         operator = self.binop[node.op.__class__.__name__]
  1373.         operator_precedence = self.binop_precedence[operator]
  1374.         with self.require_parens(operator_precedence, node):
  1375.             if operator in self.binop_rassoc:
  1376.                 left_precedence = operator_precedence.next()
  1377.                 right_precedence = operator_precedence
  1378.             else:
  1379.                 left_precedence = operator_precedence
  1380.                 right_precedence = operator_precedence.next()
  1382.             self.set_precedence(left_precedence, node.left)
  1383.             self.traverse(node.left)
  1384.             self.write(f" {operator} ")
  1385.             self.set_precedence(right_precedence, node.right)
  1386.             self.traverse(node.right)
  1388.     cmpops = {
  1389.         "Eq": "==",
  1390.         "NotEq": "!=",
  1391.         "Lt": "<",
  1392.         "LtE": "<=",
  1393.         "Gt": ">",
  1394.         "GtE": ">=",
  1395.         "Is": "is",
  1396.         "IsNot": "is not",
  1397.         "In": "in",
  1398.         "NotIn": "not in",
  1399.     }
  1401.     def visit_Compare(self, node):
  1402.         with self.require_parens(_Precedence.CMP, node):
  1403.             self.set_precedence(_Precedence.CMP.next(), node.left, *node.comparators)
  1404.             self.traverse(node.left)
  1405.             for o, e in zip(node.ops, node.comparators):
  1406.                 self.write(" " + self.cmpops[o.__class__.__name__] + " ")
  1407.                 self.traverse(e)
  1409.     boolops = {"And": "and", "Or": "or"}
  1410.     boolop_precedence = {"and": _Precedence.AND, "or": _Precedence.OR}
  1412.     def visit_BoolOp(self, node):
  1413.         operator = self.boolops[node.op.__class__.__name__]
  1414.         operator_precedence = self.boolop_precedence[operator]
  1416.         def increasing_level_traverse(node):
  1417.             nonlocal operator_precedence
  1418.             operator_precedence = operator_precedence.next()
  1419.             self.set_precedence(operator_precedence, node)
  1420.             self.traverse(node)
  1422.         with self.require_parens(operator_precedence, node):
  1423.             s = f" {operator} "
  1424.             self.interleave(lambda: self.write(s), increasing_level_traverse, node.values)
  1426.     def visit_Attribute(self, node):
  1427.         self.set_precedence(_Precedence.ATOM, node.value)
  1428.         self.traverse(node.value)
  1429.         # Special case: 3.__abs__() is a syntax error, so if node.value
  1430.         # is an integer literal then we need to either parenthesize
  1431.         # it or add an extra space to get 3 .__abs__().
  1432.         if isinstance(node.value, Constant) and isinstance(node.value.value, int):
  1433.             self.write(" ")
  1434.         self.write(".")
  1435.         self.write(node.attr)
  1437.     def visit_Call(self, node):
  1438.         self.set_precedence(_Precedence.ATOM, node.func)
  1439.         self.traverse(node.func)
  1440.         with self.delimit("(", ")"):
  1441.             comma = False
  1442.             for e in node.args:
  1443.                 if comma:
  1444.                     self.write(", ")
  1445.                 else:
  1446.                     comma = True
  1447.                 self.traverse(e)
  1448.             for e in node.keywords:
  1449.                 if comma:
  1450.                     self.write(", ")
  1451.                 else:
  1452.                     comma = True
  1453.                 self.traverse(e)
  1455.     def visit_Subscript(self, node):
  1456.         def is_simple_tuple(slice_value):
  1457.             # when unparsing a non-empty tuple, the parentheses can be safely
  1458.             # omitted if there aren't any elements that explicitly requires
  1459.             # parentheses (such as starred expressions).
  1460.             return (
  1461.                 isinstance(slice_value, Tuple)
  1462.                 and slice_value.elts
  1463.                 and not any(isinstance(elt, Starred) for elt in slice_value.elts)
  1464.             )
  1466.         self.set_precedence(_Precedence.ATOM, node.value)
  1467.         self.traverse(node.value)
  1468.         with self.delimit("[", "]"):
  1469.             if is_simple_tuple(node.slice):
  1470.                 self.items_view(self.traverse, node.slice.elts)
  1471.             else:
  1472.                 self.traverse(node.slice)
  1474.     def visit_Starred(self, node):
  1475.         self.write("*")
  1476.         self.set_precedence(_Precedence.EXPR, node.value)
  1477.         self.traverse(node.value)
  1479.     def visit_Ellipsis(self, node):
  1480.         self.write("...")
  1482.     def visit_Slice(self, node):
  1483.         if node.lower:
  1484.             self.traverse(node.lower)
  1485.         self.write(":")
  1486.         if node.upper:
  1487.             self.traverse(node.upper)
  1488.         if node.step:
  1489.             self.write(":")
  1490.             self.traverse(node.step)
  1492.     def visit_Match(self, node):
  1493.         self.fill("match ")
  1494.         self.traverse(node.subject)
  1495.         with self.block():
  1496.             for case in node.cases:
  1497.                 self.traverse(case)
  1499.     def visit_arg(self, node):
  1500.         self.write(node.arg)
  1501.         if node.annotation:
  1502.             self.write(": ")
  1503.             self.traverse(node.annotation)
  1505.     def visit_arguments(self, node):
  1506.         first = True
  1507.         # normal arguments
  1508.         all_args = node.posonlyargs + node.args
  1509.         defaults = [None] * (len(all_args) - len(node.defaults)) + node.defaults
  1510.         for index, elements in enumerate(zip(all_args, defaults), 1):
  1511.             a, d = elements
  1512.             if first:
  1513.                 first = False
  1514.             else:
  1515.                 self.write(", ")
  1516.             self.traverse(a)
  1517.             if d:
  1518.                 self.write("=")
  1519.                 self.traverse(d)
  1520.             if index == len(node.posonlyargs):
  1521.                 self.write(", /")
  1523.         # varargs, or bare '*' if no varargs but keyword-only arguments present
  1524.         if node.vararg or node.kwonlyargs:
  1525.             if first:
  1526.                 first = False
  1527.             else:
  1528.                 self.write(", ")
  1529.             self.write("*")
  1530.             if node.vararg:
  1531.                 self.write(node.vararg.arg)
  1532.                 if node.vararg.annotation:
  1533.                     self.write(": ")
  1534.                     self.traverse(node.vararg.annotation)
  1536.         # keyword-only arguments
  1537.         if node.kwonlyargs:
  1538.             for a, d in zip(node.kwonlyargs, node.kw_defaults):
  1539.                 self.write(", ")
  1540.                 self.traverse(a)
  1541.                 if d:
  1542.                     self.write("=")
  1543.                     self.traverse(d)
  1545.         # kwargs
  1546.         if node.kwarg:
  1547.             if first:
  1548.                 first = False
  1549.             else:
  1550.                 self.write(", ")
  1551.             self.write("**" + node.kwarg.arg)
  1552.             if node.kwarg.annotation:
  1553.                 self.write(": ")
  1554.                 self.traverse(node.kwarg.annotation)
  1556.     def visit_keyword(self, node):
  1557.         if node.arg is None:
  1558.             self.write("**")
  1559.         else:
  1560.             self.write(node.arg)
  1561.             self.write("=")
  1562.         self.traverse(node.value)
  1564.     def visit_Lambda(self, node):
  1565.         with self.require_parens(_Precedence.TEST, node):
  1566.             self.write("lambda ")
  1567.             self.traverse(node.args)
  1568.             self.write(": ")
  1569.             self.set_precedence(_Precedence.TEST, node.body)
  1570.             self.traverse(node.body)
  1572.     def visit_alias(self, node):
  1573.         self.write(node.name)
  1574.         if node.asname:
  1575.             self.write(" as " + node.asname)
  1577.     def visit_withitem(self, node):
  1578.         self.traverse(node.context_expr)
  1579.         if node.optional_vars:
  1580.             self.write(" as ")
  1581.             self.traverse(node.optional_vars)
  1583.     def visit_match_case(self, node):
  1584.         self.fill("case ")
  1585.         self.traverse(node.pattern)
  1586.         if node.guard:
  1587.             self.write(" if ")
  1588.             self.traverse(node.guard)
  1589.         with self.block():
  1590.             self.traverse(node.body)
  1592.     def visit_MatchValue(self, node):
  1593.         self.traverse(node.value)
  1595.     def visit_MatchSingleton(self, node):
  1596.         self._write_constant(node.value)
  1598.     def visit_MatchSequence(self, node):
  1599.         with self.delimit("[", "]"):
  1600.             self.interleave(
  1601.                 lambda: self.write(", "), self.traverse, node.patterns
  1602.             )
  1604.     def visit_MatchStar(self, node):
  1605.         name = node.name
  1606.         if name is None:
  1607.             name = "_"
  1608.         self.write(f"*{name}")
  1610.     def visit_MatchMapping(self, node):
  1611.         def write_key_pattern_pair(pair):
  1612.             k, p = pair
  1613.             self.traverse(k)
  1614.             self.write(": ")
  1615.             self.traverse(p)
  1617.         with self.delimit("{", "}"):
  1618.             keys = node.keys
  1619.             self.interleave(
  1620.                 lambda: self.write(", "),
  1621.                 write_key_pattern_pair,
  1622.                 zip(keys, node.patterns, strict=True),
  1623.             )
  1624.             rest = node.rest
  1625.             if rest is not None:
  1626.                 if keys:
  1627.                     self.write(", ")
  1628.                 self.write(f"**{rest}")
  1630.     def visit_MatchClass(self, node):
  1631.         self.set_precedence(_Precedence.ATOM, node.cls)
  1632.         self.traverse(node.cls)
  1633.         with self.delimit("(", ")"):
  1634.             patterns = node.patterns
  1635.             self.interleave(
  1636.                 lambda: self.write(", "), self.traverse, patterns
  1637.             )
  1638.             attrs = node.kwd_attrs
  1639.             if attrs:
  1640.                 def write_attr_pattern(pair):
  1641.                     attr, pattern = pair
  1642.                     self.write(f"{attr}=")
  1643.                     self.traverse(pattern)
  1645.                 if patterns:
  1646.                     self.write(", ")
  1647.                 self.interleave(
  1648.                     lambda: self.write(", "),
  1649.                     write_attr_pattern,
  1650.                     zip(attrs, node.kwd_patterns, strict=True),
  1651.                 )
  1653.     def visit_MatchAs(self, node):
  1654.         name = node.name
  1655.         pattern = node.pattern
  1656.         if name is None:
  1657.             self.write("_")
  1658.         elif pattern is None:
  1659.             self.write(node.name)
  1660.         else:
  1661.             with self.require_parens(_Precedence.TEST, node):
  1662.                 self.set_precedence(_Precedence.BOR, node.pattern)
  1663.                 self.traverse(node.pattern)
  1664.                 self.write(f" as {node.name}")
  1666.     def visit_MatchOr(self, node):
  1667.         with self.require_parens(_Precedence.BOR, node):
  1668.             self.set_precedence(_Precedence.BOR.next(), *node.patterns)
  1669.             self.interleave(lambda: self.write(" | "), self.traverse, node.patterns)
  1671. def unparse(ast_obj):
  1672.     unparser = _Unparser()
  1673.     return unparser.visit(ast_obj)
  1676. def main():
  1677.     import argparse
  1679.     parser = argparse.ArgumentParser(prog='python -m ast')
  1680.     parser.add_argument('infile', type=argparse.FileType(mode='rb'), nargs='?',
  1681.                         default='-',
  1682.                         help='the file to parse; defaults to stdin')
  1683.     parser.add_argument('-m', '--mode', default='exec',
  1684.                         choices=('exec', 'single', 'eval', 'func_type'),
  1685.                         help='specify what kind of code must be parsed')
  1686.     parser.add_argument('--no-type-comments', default=True, action='store_false',
  1687.                         help="don't add information about type comments")
  1688.     parser.add_argument('-a', '--include-attributes', action='store_true',
  1689.                         help='include attributes such as line numbers and '
  1690.                              'column offsets')
  1691.     parser.add_argument('-i', '--indent', type=int, default=3,
  1692.                         help='indentation of nodes (number of spaces)')
  1693.     args = parser.parse_args()
  1695.     with args.infile as infile:
  1696.         source = infile.read()
  1697.     tree = parse(source, args.infile.name, args.mode, type_comments=args.no_type_comments)
  1698.     print(dump(tree, include_attributes=args.include_attributes, indent=args.indent))
  1700. if __name__ == '__main__':
  1701.     main()