"""

ast

~~~

The `ast` module helps Python applications to process trees of the Python

abstract syntax grammar. The abstract syntax itself might change with

each Python release; this module helps to find out programmatically what

the current grammar looks like and allows modifications of it.

An abstract syntax tree can be generated by passing `ast.PyCF_ONLY_AST` as

a flag to the `compile()` builtin function or by using the `parse()`

function from this module. The result will be a tree of objects whose

classes all inherit from `ast.AST`.

A modified abstract syntax tree can be compiled into a Python code object

using the built-in `compile()` function.

Additionally various helper functions are provided that make working with

the trees simpler. The main intention of the helper functions and this

module in general is to provide an easy to use interface for libraries

that work tightly with the python syntax (template engines for example).

:copyright: Copyright 2008 by Armin Ronacher.

:license: Python License.

"""

import sys

import re

from _ast import *

from contextlib import contextmanager, nullcontext

from enum import IntEnum, auto, _simple_enum

def parse(source, filename='<unknown>', mode='exec', *,

type_comments=False, feature_version=None, optimize=-1):

"""

Parse the source into an AST node.

Equivalent to compile(source, filename, mode, PyCF_ONLY_AST).

Pass type_comments=True to get back type comments where the syntax allows.

"""

flags = PyCF_ONLY_AST

if optimize > 0:

flags |= PyCF_OPTIMIZED_AST

if type_comments:

flags |= PyCF_TYPE_COMMENTS

if feature_version is None:

feature_version = -1

elif isinstance(feature_version, tuple):

major, minor = feature_version # Should be a 2-tuple.

if major != 3:

raise ValueError(f"Unsupported major version: {major}")

feature_version = minor

# Else it should be an int giving the minor version for 3.x.

return compile(source, filename, mode, flags,

_feature_version=feature_version, optimize=optimize)

def literal_eval(node_or_string):

"""

Evaluate an expression node or a string containing only a Python

expression. The string or node provided may only consist of the following

Python literal structures: strings, bytes, numbers, tuples, lists, dicts,

sets, booleans, and None.

Caution: A complex expression can overflow the C stack and cause a crash.

"""

if isinstance(node_or_string, str):

node_or_string = parse(node_or_string.lstrip(" \t"), mode='eval')

if isinstance(node_or_string, Expression):

node_or_string = node_or_string.body

def _raise_malformed_node(node):

msg = "malformed node or string"

if lno := getattr(node, 'lineno', None):

msg += f' on line {lno}'

raise ValueError(msg + f': {node!r}')

def _convert_num(node):

if not isinstance(node, Constant) or type(node.value) not in (int, float, complex):

_raise_malformed_node(node)

return node.value

def _convert_signed_num(node):

if isinstance(node, UnaryOp) and isinstance(node.op, (UAdd, USub)):

operand = _convert_num(node.operand)

if isinstance(node.op, UAdd):

return + operand

else:

return - operand

return _convert_num(node)

def _convert(node):

if isinstance(node, Constant):

return node.value

elif isinstance(node, Tuple):

return tuple(map(_convert, node.elts))

elif isinstance(node, List):

return list(map(_convert, node.elts))

elif isinstance(node, Set):

return set(map(_convert, node.elts))

elif (isinstance(node, Call) and isinstance(node.func, Name) and

node.func.id == 'set' and node.args == node.keywords == []):

return set()

elif isinstance(node, Dict):

if len(node.keys) != len(node.values):

_raise_malformed_node(node)

return dict(zip(map(_convert, node.keys),

map(_convert, node.values)))

elif isinstance(node, BinOp) and isinstance(node.op, (Add, Sub)):

left = _convert_signed_num(node.left)

right = _convert_num(node.right)

if isinstance(left, (int, float)) and isinstance(right, complex):

if isinstance(node.op, Add):

return left + right

else:

return left - right

return _convert_signed_num(node)

return _convert(node_or_string)

def dump(node, annotate_fields=True, include_attributes=False, *, indent=None):

"""

Return a formatted dump of the tree in node. This is mainly useful for

debugging purposes. If annotate_fields is true (by default),

the returned string will show the names and the values for fields.

If annotate_fields is false, the result string will be more compact by

omitting unambiguous field names. Attributes such as line

numbers and column offsets are not dumped by default. If this is wanted,

include_attributes can be set to true. If indent is a non-negative

integer or string, then the tree will be pretty-printed with that indent

level. None (the default) selects the single line representation.

"""

def _format(node, level=0):

if indent is not None:

level += 1

prefix = '\n' + indent * level

sep = ',\n' + indent * level

else:

prefix = ''

sep = ', '

if isinstance(node, AST):

cls = type(node)

args = []

allsimple = True

keywords = annotate_fields

for name in node._fields:

try:

value = getattr(node, name)

except AttributeError:

keywords = True

continue

if value is None and getattr(cls, name, ...) is None:

keywords = True

continue

value, simple = _format(value, level)

allsimple = allsimple and simple

if keywords:

args.append('%s=%s' % (name, value))

else:

args.append(value)

if include_attributes and node._attributes:

for name in node._attributes:

try:

value = getattr(node, name)

except AttributeError:

continue

if value is None and getattr(cls, name, ...) is None:

continue

value, simple = _format(value, level)

allsimple = allsimple and simple

args.append('%s=%s' % (name, value))

if allsimple and len(args) <= 3:

return '%s(%s)' % (node.__class__.__name__, ', '.join(args)), not args

return '%s(%s%s)' % (node.__class__.__name__, prefix, sep.join(args)), False

elif isinstance(node, list):

if not node:

return '[]', True

return '[%s%s]' % (prefix, sep.join(_format(x, level)[0] for x in node)), False

return repr(node), True

if not isinstance(node, AST):

raise TypeError('expected AST, got %r' % node.__class__.__name__)

if indent is not None and not isinstance(indent, str):

indent = ' ' * indent

return _format(node)[0]

def copy_location(new_node, old_node):

"""

Copy source location (`lineno`, `col_offset`, `end_lineno`, and `end_col_offset`

attributes) from *old_node* to *new_node* if possible, and return *new_node*.

"""

for attr in 'lineno', 'col_offset', 'end_lineno', 'end_col_offset':

if attr in old_node._attributes and attr in new_node._attributes:

value = getattr(old_node, attr, None)

# end_lineno and end_col_offset are optional attributes, and they

# should be copied whether the value is None or not.

if value is not None or (

hasattr(old_node, attr) and attr.startswith("end_")

):

setattr(new_node, attr, value)

return new_node

def fix_missing_locations(node):

"""

When you compile a node tree with compile(), the compiler expects lineno and

col_offset attributes for every node that supports them. This is rather

tedious to fill in for generated nodes, so this helper adds these attributes

recursively where not already set, by setting them to the values of the

parent node. It works recursively starting at *node*.

"""

def _fix(node, lineno, col_offset, end_lineno, end_col_offset):

if 'lineno' in node._attributes:

if not hasattr(node, 'lineno'):

node.lineno = lineno

else:

lineno = node.lineno

if 'end_lineno' in node._attributes:

if getattr(node, 'end_lineno', None) is None:

node.end_lineno = end_lineno

else:

end_lineno = node.end_lineno

if 'col_offset' in node._attributes:

if not hasattr(node, 'col_offset'):

node.col_offset = col_offset

else:

col_offset = node.col_offset

if 'end_col_offset' in node._attributes:

if getattr(node, 'end_col_offset', None) is None:

node.end_col_offset = end_col_offset

else:

end_col_offset = node.end_col_offset

for child in iter_child_nodes(node):

_fix(child, lineno, col_offset, end_lineno, end_col_offset)

_fix(node, 1, 0, 1, 0)

return node

def increment_lineno(node, n=1):

"""

Increment the line number and end line number of each node in the tree

starting at *node* by *n*. This is useful to "move code" to a different

location in a file.

"""

for child in walk(node):

# TypeIgnore is a special case where lineno is not an attribute

# but rather a field of the node itself.

if isinstance(child, TypeIgnore):

child.lineno = getattr(child, 'lineno', 0) + n

continue

if 'lineno' in child._attributes:

child.lineno = getattr(child, 'lineno', 0) + n

if (

"end_lineno" in child._attributes

and (end_lineno := getattr(child, "end_lineno", 0)) is not None

):

child.end_lineno = end_lineno + n

return node

def iter_fields(node):

"""

Yield a tuple of ``(fieldname, value)`` for each field in ``node._fields``

that is present on *node*.

"""

for field in node._fields:

try:

yield field, getattr(node, field)

except AttributeError:

pass

def iter_child_nodes(node):

"""

Yield all direct child nodes of *node*, that is, all fields that are nodes

and all items of fields that are lists of nodes.

"""

for name, field in iter_fields(node):

if isinstance(field, AST):

yield field

elif isinstance(field, list):

for item in field:

if isinstance(item, AST):

yield item

def get_docstring(node, clean=True):

"""

Return the docstring for the given node or None if no docstring can

be found. If the node provided does not have docstrings a TypeError

will be raised.

If *clean* is `True`, all tabs are expanded to spaces and any whitespace

that can be uniformly removed from the second line onwards is removed.

"""

if not isinstance(node, (AsyncFunctionDef, FunctionDef, ClassDef, Module)):

raise TypeError("%r can't have docstrings" % node.__class__.__name__)

if not(node.body and isinstance(node.body[0], Expr)):

return None

node = node.body[0].value

if isinstance(node, Constant) and isinstance(node.value, str):

text = node.value

else:

return None

if clean:

import inspect

text = inspect.cleandoc(text)

return text

_line_pattern = re.compile(r"(.*?(?:\r\n|\n|\r|$))")

def _splitlines_no_ff(source, maxlines=None):

"""Split a string into lines ignoring form feed and other chars.

This mimics how the Python parser splits source code.

"""

lines = []

for lineno, match in enumerate(_line_pattern.finditer(source), 1):

if maxlines is not None and lineno > maxlines:

break

lines.append(match[0])

return lines

def _pad_whitespace(source):

r"""Replace all chars except '\f\t' in a line with spaces."""

result = ''

for c in source:

if c in '\f\t':

result += c

else:

result += ' '

return result

def get_source_segment(source, node, *, padded=False):

"""Get source code segment of the *source* that generated *node*.

If some location information (`lineno`, `end_lineno`, `col_offset`,

or `end_col_offset`) is missing, return None.

If *padded* is `True`, the first line of a multi-line statement will

be padded with spaces to match its original position.

"""

try:

if node.end_lineno is None or node.end_col_offset is None:

return None

lineno = node.lineno - 1

end_lineno = node.end_lineno - 1

col_offset = node.col_offset

end_col_offset = node.end_col_offset

except AttributeError:

return None

lines = _splitlines_no_ff(source, maxlines=end_lineno+1)

if end_lineno == lineno:

return lines[lineno].encode()[col_offset:end_col_offset].decode()

if padded:

padding = _pad_whitespace(lines[lineno].encode()[:col_offset].decode())

else:

padding = ''

first = padding + lines[lineno].encode()[col_offset:].decode()

last = lines[end_lineno].encode()[:end_col_offset].decode()

lines = lines[lineno+1:end_lineno]

lines.insert(0, first)

lines.append(last)

return ''.join(lines)

def walk(node):

"""

Recursively yield all descendant nodes in the tree starting at *node*

(including *node* itself), in no specified order. This is useful if you

only want to modify nodes in place and don't care about the context.

"""

from collections import deque

todo = deque([node])

while todo:

node = todo.popleft()

todo.extend(iter_child_nodes(node))

yield node

class NodeVisitor(object):

"""

A node visitor base class that walks the abstract syntax tree and calls a

visitor function for every node found. This function may return a value

which is forwarded by the `visit` method.

This class is meant to be subclassed, with the subclass adding visitor

methods.

Per default the visitor functions for the nodes are ``'visit_'`` +

class name of the node. So a `TryFinally` node visit function would

be `visit_TryFinally`. This behavior can be changed by overriding

the `visit` method. If no visitor function exists for a node

(return value `None`) the `generic_visit` visitor is used instead.

Don't use the `NodeVisitor` if you want to apply changes to nodes during

traversing. For this a special visitor exists (`NodeTransformer`) that

allows modifications.

"""

def visit(self, node):

"""Visit a node."""

method = 'visit_' + node.__class__.__name__

visitor = getattr(self, method, self.generic_visit)

return visitor(node)

def generic_visit(self, node):

"""Called if no explicit visitor function exists for a node."""

for field, value in iter_fields(node):

if isinstance(value, list):

for item in value:

if isinstance(item, AST):

self.visit(item)

elif isinstance(value, AST):

self.visit(value)

def visit_Constant(self, node):

value = node.value

type_name = _const_node_type_names.get(type(value))

if type_name is None:

for cls, name in _const_node_type_names.items():

if isinstance(value, cls):

type_name = name

break

if type_name is not None:

method = 'visit_' + type_name

try:

visitor = getattr(self, method)

except AttributeError:

pass

else:

import warnings

warnings.warn(f"{method} is deprecated; add visit_Constant",

DeprecationWarning, 2)

return visitor(node)

return self.generic_visit(node)

class NodeTransformer(NodeVisitor):

"""

A :class:`NodeVisitor` subclass that walks the abstract syntax tree and

allows modification of nodes.

The `NodeTransformer` will walk the AST and use the return value of the

visitor methods to replace or remove the old node. If the return value of

the visitor method is ``None``, the node will be removed from its location,

otherwise it is replaced with the return value. The return value may be the

original node in which case no replacement takes place.

Here is an example transformer that rewrites all occurrences of name lookups

(``foo``) to ``data['foo']``::

class RewriteName(NodeTransformer):

def visit_Name(self, node):

return Subscript(

value=Name(id='data', ctx=Load()),

slice=Constant(value=node.id),

ctx=node.ctx

)

Keep in mind that if the node you're operating on has child nodes you must

either transform the child nodes yourself or call the :meth:`generic_visit`

method for the node first.

For nodes that were part of a collection of statements (that applies to all

statement nodes), the visitor may also return a list of nodes rather than

just a single node.

Usually you use the transformer like this::

node = YourTransformer().visit(node)

"""

def generic_visit(self, node):

for field, old_value in iter_fields(node):

if isinstance(old_value, list):

new_values = []

for value in old_value:

if isinstance(value, AST):

value = self.visit(value)

if value is None:

continue

elif not isinstance(value, AST):

new_values.extend(value)

continue

new_values.append(value)

old_value[:] = new_values

elif isinstance(old_value, AST):

new_node = self.visit(old_value)

if new_node is None:

delattr(node, field)

else:

setattr(node, field, new_node)

return node

_DEPRECATED_VALUE_ALIAS_MESSAGE = (

"{name} is deprecated and will be removed in Python {remove}; use value instead"

)

_DEPRECATED_CLASS_MESSAGE = (

"{name} is deprecated and will be removed in Python {remove}; "

"use ast.Constant instead"

)

# If the ast module is loaded more than once, only add deprecated methods once

if not hasattr(Constant, 'n'):

# The following code is for backward compatibility.

# It will be removed in future.

def _n_getter(self):

"""Deprecated. Use value instead."""

import warnings

warnings._deprecated(

"Attribute n", message=_DEPRECATED_VALUE_ALIAS_MESSAGE, remove=(3, 14)

)

return self.value

def _n_setter(self, value):

import warnings

warnings._deprecated(

"Attribute n", message=_DEPRECATED_VALUE_ALIAS_MESSAGE, remove=(3, 14)

)

self.value = value

def _s_getter(self):

"""Deprecated. Use value instead."""

import warnings

warnings._deprecated(

"Attribute s", message=_DEPRECATED_VALUE_ALIAS_MESSAGE, remove=(3, 14)

)

return self.value

def _s_setter(self, value):

import warnings

warnings._deprecated(

"Attribute s", message=_DEPRECATED_VALUE_ALIAS_MESSAGE, remove=(3, 14)

)

self.value = value

Constant.n = property(_n_getter, _n_setter)

Constant.s = property(_s_getter, _s_setter)

class _ABC(type):

def __init__(cls, *args):

cls.__doc__ = """Deprecated AST node class. Use ast.Constant instead"""

def __instancecheck__(cls, inst):

if cls in _const_types:

import warnings

warnings._deprecated(

f"ast.{cls.__qualname__}",

message=_DEPRECATED_CLASS_MESSAGE,

remove=(3, 14)

)

if not isinstance(inst, Constant):

return False

if cls in _const_types:

try:

value = inst.value

except AttributeError:

return False

else:

return (

isinstance(value, _const_types[cls]) and

not isinstance(value, _const_types_not.get(cls, ()))

)

return type.__instancecheck__(cls, inst)

def _new(cls, *args, **kwargs):

for key in kwargs:

if key not in cls._fields:

# arbitrary keyword arguments are accepted

continue

pos = cls._fields.index(key)

if pos < len(args):

raise TypeError(f"{cls.__name__} got multiple values for argument {key!r}")

if cls in _const_types:

import warnings

warnings._deprecated(

f"ast.{cls.__qualname__}", message=_DEPRECATED_CLASS_MESSAGE, remove=(3, 14)

)

return Constant(*args, **kwargs)

return Constant.__new__(cls, *args, **kwargs)

class Num(Constant, metaclass=_ABC):

_fields = ('n',)

__new__ = _new

class Str(Constant, metaclass=_ABC):

_fields = ('s',)

__new__ = _new

class Bytes(Constant, metaclass=_ABC):

_fields = ('s',)

__new__ = _new

class NameConstant(Constant, metaclass=_ABC):

__new__ = _new

class Ellipsis(Constant, metaclass=_ABC):

_fields = ()

def __new__(cls, *args, **kwargs):

if cls is _ast_Ellipsis:

import warnings

warnings._deprecated(

"ast.Ellipsis", message=_DEPRECATED_CLASS_MESSAGE, remove=(3, 14)

)

return Constant(..., *args, **kwargs)

return Constant.__new__(cls, *args, **kwargs)

# Keep another reference to Ellipsis in the global namespace

# so it can be referenced in Ellipsis.__new__

# (The original "Ellipsis" name is removed from the global namespace later on)

_ast_Ellipsis = Ellipsis

_const_types = {

Num: (int, float, complex),

Str: (str,),

Bytes: (bytes,),

NameConstant: (type(None), bool),

Ellipsis: (type(...),),

}

_const_types_not = {

Num: (bool,),

}

_const_node_type_names = {

bool: 'NameConstant', # should be before int

type(None): 'NameConstant',

int: 'Num',

float: 'Num',

complex: 'Num',

str: 'Str',

bytes: 'Bytes',

type(...): 'Ellipsis',

}

class slice(AST):

"""Deprecated AST node class."""

class Index(slice):

"""Deprecated AST node class. Use the index value directly instead."""

def __new__(cls, value, **kwargs):

return value

class ExtSlice(slice):

"""Deprecated AST node class. Use ast.Tuple instead."""

def __new__(cls, dims=(), **kwargs):

return Tuple(list(dims), Load(), **kwargs)

# If the ast module is loaded more than once, only add deprecated methods once

if not hasattr(Tuple, 'dims'):

# The following code is for backward compatibility.

# It will be removed in future.

def _dims_getter(self):

"""Deprecated. Use elts instead."""

return self.elts

def _dims_setter(self, value):

self.elts = value

Tuple.dims = property(_dims_getter, _dims_setter)

class Suite(mod):

"""Deprecated AST node class. Unused in Python 3."""

class AugLoad(expr_context):

"""Deprecated AST node class. Unused in Python 3."""

class AugStore(expr_context):

"""Deprecated AST node class. Unused in Python 3."""

class Param(expr_context):

"""Deprecated AST node class. Unused in Python 3."""

# Large float and imaginary literals get turned into infinities in the AST.

# We unparse those infinities to INFSTR.

_INFSTR = "1e" + repr(sys.float_info.max_10_exp + 1)

@_simple_enum(IntEnum)

class _Precedence:

"""Precedence table that originated from python grammar."""

NAMED_EXPR = auto() # <target> := <expr1>

TUPLE = auto() # <expr1>, <expr2>

YIELD = auto() # 'yield', 'yield from'

TEST = auto() # 'if'-'else', 'lambda'

OR = auto() # 'or'

AND = auto() # 'and'

NOT = auto() # 'not'

CMP = auto() # '<', '>', '==', '>=', '<=', '!=',

# 'in', 'not in', 'is', 'is not'

EXPR = auto()

BOR = EXPR # '|'

BXOR = auto() # '^'

BAND = auto() # '&'

SHIFT = auto() # '<<', '>>'

ARITH = auto() # '+', '-'

TERM = auto() # '*', '@', '/', '%', '//'

FACTOR = auto() # unary '+', '-', '~'

POWER = auto() # '**'

AWAIT = auto() # 'await'

ATOM = auto()

def next(self):

try:

return self.__class__(self + 1)

except ValueError:

return self

_SINGLE_QUOTES = ("'", '"')

_MULTI_QUOTES = ('"""', "'''")

_ALL_QUOTES = (*_SINGLE_QUOTES, *_MULTI_QUOTES)

class _Unparser(NodeVisitor):

"""Methods in this class recursively traverse an AST and

output source code for the abstract syntax; original formatting

is disregarded."""

def __init__(self):

self._source = []

self._precedences = {}

self._type_ignores = {}

self._indent = 0

self._in_try_star = False

def interleave(self, inter, f, seq):

"""Call f on each item in seq, calling inter() in between."""

seq = iter(seq)

try:

f(next(seq))

except StopIteration:

pass

else:

for x in seq:

inter()

f(x)

def items_view(self, traverser, items):

"""Traverse and separate the given *items* with a comma and append it to

the buffer. If *items* is a single item sequence, a trailing comma

will be added."""

if len(items) == 1:

traverser(items[0])

self.write(",")

else:

self.interleave(lambda: self.write(", "), traverser, items)

def maybe_newline(self):

"""Adds a newline if it isn't the start of generated source"""

if self._source:

self.write("\n")

def fill(self, text=""):

"""Indent a piece of text and append it, according to the current

indentation level"""

self.maybe_newline()

self.write(" " * self._indent + text)

def write(self, *text):

"""Add new source parts"""

self._source.extend(text)

@contextmanager

def buffered(self, buffer = None):

if buffer is None:

buffer = []

original_source = self._source

self._source = buffer

yield buffer

self._source = original_source

@contextmanager

def block(self, *, extra = None):

"""A context manager for preparing the source for blocks. It adds

the character':', increases the indentation on enter and decreases

the indentation on exit. If *extra* is given, it will be directly

appended after the colon character.

"""

self.write(":")

if extra:

self.write(extra)

self._indent += 1

yield

self._indent -= 1

@contextmanager

def delimit(self, start, end):

"""A context manager for preparing the source for expressions. It adds

*start* to the buffer and enters, after exit it adds *end*."""

self.write(start)

yield

self.write(end)

def delimit_if(self, start, end, condition):

if condition:

return self.delimit(start, end)

else:

return nullcontext()

def require_parens(self, precedence, node):

"""Shortcut to adding precedence related parens"""

return self.delimit_if("(", ")", self.get_precedence(node) > precedence)

def get_precedence(self, node):

return self._precedences.get(node, _Precedence.TEST)

def set_precedence(self, precedence, *nodes):

for node in nodes:

self._precedences[node] = precedence

def get_raw_docstring(self, node):

"""If a docstring node is found in the body of the *node* parameter,

return that docstring node, None otherwise.

Logic mirrored from ``_PyAST_GetDocString``."""

if not isinstance(

node, (AsyncFunctionDef, FunctionDef, ClassDef, Module)

) or len(node.body) < 1:

return None

node = node.body[0]

if not isinstance(node, Expr):

return None

node = node.value

if isinstance(node, Constant) and isinstance(node.value, str):

return node

def get_type_comment(self, node):

comment = self._type_ignores.get(node.lineno) or node.type_comment

if comment is not None:

return f" # type: {comment}"

def traverse(self, node):

if isinstance(node, list):

for item in node:

self.traverse(item)

else:

super().visit(node)

# Note: as visit() resets the output text, do NOT rely on

# NodeVisitor.generic_visit to handle any nodes (as it calls back in to

# the subclass visit() method, which resets self._source to an empty list)

def visit(self, node):

"""Outputs a source code string that, if converted back to an ast

(using ast.parse) will generate an AST equivalent to *node*"""

self._source = []

self.traverse(node)

return "".join(self._source)

def _write_docstring_and_traverse_body(self, node):

if (docstring := self.get_raw_docstring(node)):

self._write_docstring(docstring)

self.traverse(node.body[1:])

else:

self.traverse(node.body)

def visit_Module(self, node):

self._type_ignores = {

ignore.lineno: f"ignore{ignore.tag}"

for ignore in node.type_ignores

}

self._write_docstring_and_traverse_body(node)

self._type_ignores.clear()

def visit_FunctionType(self, node):

with self.delimit("(", ")"):

self.interleave(

lambda: self.write(", "), self.traverse, node.argtypes

)

self.write(" -> ")

self.traverse(node.returns)

def visit_Expr(self, node):

self.fill()

self.set_precedence(_Precedence.YIELD, node.value)

self.traverse(node.value)

def visit_NamedExpr(self, node):

with self.require_parens(_Precedence.NAMED_EXPR, node):

self.set_precedence(_Precedence.ATOM, node.target, node.value)

self.traverse(node.target)

self.write(" := ")

self.traverse(node.value)

def visit_Import(self, node):

self.fill("import ")

self.interleave(lambda: self.write(", "), self.traverse, node.names)

def visit_ImportFrom(self, node):

self.fill("from ")

self.write("." * (node.level or 0))

if node.module:

self.write(node.module)

self.write(" import ")

self.interleave(lambda: self.write(", "), self.traverse, node.names)

def visit_Assign(self, node):

self.fill()

for target in node.targets:

self.set_precedence(_Precedence.TUPLE, target)

self.traverse(target)

self.write(" = ")

self.traverse(node.value)

if type_comment := self.get_type_comment(node):

self.write(type_comment)

def visit_AugAssign(self, node):

self.fill()

self.traverse(node.target)

self.write(" " + self.binop[node.op.__class__.__name__] + "= ")

self.traverse(node.value)

def visit_AnnAssign(self, node):

self.fill()

with self.delimit_if("(", ")", not node.simple and isinstance(node.target, Name)):

self.traverse(node.target)

self.write(": ")

self.traverse(node.annotation)

if node.value:

self.write(" = ")

self.traverse(node.value)

def visit_Return(self, node):

self.fill("return")

if node.value:

self.write(" ")

self.traverse(node.value)

def visit_Pass(self, node):

self.fill("pass")

def visit_Break(self, node):

self.fill("break")

def visit_Continue(self, node):

self.fill("continue")

def visit_Delete(self, node):

self.fill("del ")

self.interleave(lambda: self.write(", "), self.traverse, node.targets)

def visit_Assert(self, node):

self.fill("assert ")

self.traverse(node.test)

if node.msg:

self.write(", ")

self.traverse(node.msg)

def visit_Global(self, node):

self.fill("global ")

self.interleave(lambda: self.write(", "), self.write, node.names)

def visit_Nonlocal(self, node):

self.fill("nonlocal ")

self.interleave(lambda: self.write(", "), self.write, node.names)

def visit_Await(self, node):

with self.require_parens(_Precedence.AWAIT, node):

self.write("await")

if node.value:

self.write(" ")

self.set_precedence(_Precedence.ATOM, node.value)

self.traverse(node.value)

def visit_Yield(self, node):

with self.require_parens(_Precedence.YIELD, node):

self.write("yield")

if node.value:

self.write(" ")

self.set_precedence(_Precedence.ATOM, node.value)

self.traverse(node.value)

def visit_YieldFrom(self, node):

with self.require_parens(_Precedence.YIELD, node):

self.write("yield from ")

if not node.value:

raise ValueError("Node can't be used without a value attribute.")

self.set_precedence(_Precedence.ATOM, node.value)

self.traverse(node.value)

def visit_Raise(self, node):

self.fill("raise")

if not node.exc:

if node.cause:

raise ValueError(f"Node can't use cause without an exception.")

return