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Edit File: ast.py
""" 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 from _ast import * from contextlib import contextmanager, nullcontext from enum import IntEnum, auto def parse(source, filename='<unknown>', mode='exec', *, type_comments=False, feature_version=None): """ 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 type_comments: flags |= PyCF_TYPE_COMMENTS if isinstance(feature_version, tuple): major, minor = feature_version # Should be a 2-tuple. assert major == 3 feature_version = minor elif feature_version is None: feature_version = -1 # Else it should be an int giving the minor version for 3.x. return compile(source, filename, mode, flags, _feature_version=feature_version) 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, mode='eval') if isinstance(node_or_string, Expression): node_or_string = node_or_string.body def _raise_malformed_node(node): raise ValueError(f'malformed node or string: {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): 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, Str): text = node.s elif isinstance(node, Constant) and isinstance(node.value, str): text = node.value else: return None if clean: import inspect text = inspect.cleandoc(text) return text def _splitlines_no_ff(source): """Split a string into lines ignoring form feed and other chars. This mimics how the Python parser splits source code. """ idx = 0 lines = [] next_line = '' while idx < len(source): c = source[idx] next_line += c idx += 1 # Keep \r\n together if c == '\r' and idx < len(source) and source[idx] == '\n': next_line += '\n' idx += 1 if c in '\r\n': lines.append(next_line) next_line = '' if next_line: lines.append(next_line) 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) 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 # 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 _getter(self): """Deprecated. Use value instead.""" return self.value def _setter(self, value): self.value = value Constant.n = property(_getter, _setter) Constant.s = property(_getter, _setter) class _ABC(type): def __init__(cls, *args): cls.__doc__ = """Deprecated AST node class. Use ast.Constant instead""" def __instancecheck__(cls, inst): 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: 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 Ellipsis: return Constant(..., *args, **kwargs) return Constant.__new__(cls, *args, **kwargs) _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) class _Precedence(IntEnum): """Precedence table that originated from python grammar.""" TUPLE = auto() 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, *, _avoid_backslashes=False): self._source = [] self._buffer = [] self._precedences = {} self._type_ignores = {} self._indent = 0 self._avoid_backslashes = _avoid_backslashes 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): """Append a piece of text""" self._source.append(text) def buffer_writer(self, text): self._buffer.append(text) @property def buffer(self): value = "".join(self._buffer) self._buffer.clear() return value @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) 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.TUPLE, 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) 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.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 self.write(" ") self.traverse(node.exc) if node.cause: self.write(" from ") self.traverse(node.cause) def visit_Try(self, node): self.fill("try") with self.block(): self.traverse(node.body) for ex in node.handlers: self.traverse(ex) if node.orelse: self.fill("else") with self.block(): self.traverse(node.orelse) if node.finalbody: self.fill("finally") with self.block(): self.traverse(node.finalbody) def visit_ExceptHandler(self, node): self.fill("except") if node.type: self.write(" ") self.traverse(node.type) if node.name: self.write(" as ") self.write(node.name) with self.block(): self.traverse(node.body) def visit_ClassDef(self, node): self.maybe_newline() for deco in node.decorator_list: self.fill("@") self.traverse(deco) self.fill("class " + node.name) with self.delimit_if("(", ")", condition = node.bases or node.keywords): comma = False for e in node.bases: if comma: self.write(", ") else: comma = True self.traverse(e) for e in node.keywords: if comma: self.write(", ") else: comma = True self.traverse(e) with self.block(): self._write_docstring_and_traverse_body(node) def visit_FunctionDef(self, node): self._function_helper(node, "def") def visit_AsyncFunctionDef(self, node): self._function_helper(node, "async def") def _function_helper(self, node, fill_suffix): self.maybe_newline() for deco in node.decorator_list: self.fill("@") self.traverse(deco) def_str = fill_suffix + " " + node.name self.fill(def_str) with self.delimit("(", ")"): self.traverse(node.args) if node.returns: self.write(" -> ") self.traverse(node.returns) with self.block(extra=self.get_type_comment(node)): self._write_docstring_and_traverse_body(node) def visit_For(self, node): self._for_helper("for ", node) def visit_AsyncFor(self, node): self._for_helper("async for ", node) def _for_helper(self, fill, node): self.fill(fill) self.traverse(node.target) self.write(" in ") self.traverse(node.iter) with self.block(extra=self.get_type_comment(node)): self.traverse(node.body) if node.orelse: self.fill("else") with self.block(): self.traverse(node.orelse) def visit_If(self, node): self.fill("if ") self.traverse(node.test) with self.block(): self.traverse(node.body) # collapse nested ifs into equivalent elifs. while node.orelse and len(node.orelse) == 1 and isinstance(node.orelse[0], If): node = node.orelse[0] self.fill("elif ") self.traverse(node.test) with self.block(): self.traverse(node.body) # final else if node.orelse: self.fill("else") with self.block(): self.traverse(node.orelse) def visit_While(self, node): self.fill("while ") self.traverse(node.test) with self.block(): self.traverse(node.body) if node.orelse: self.fill("else") with self.block(): self.traverse(node.orelse) def visit_With(self, node): self.fill("with ") self.interleave(lambda: self.write(", "), self.traverse, node.items) with self.block(extra=self.get_type_comment(node)): self.traverse(node.body) def visit_AsyncWith(self, node): self.fill("async with ") self.interleave(lambda: self.write(", "), self.traverse, node.items) with self.block(extra=self.get_type_comment(node)): self.traverse(node.body) def _str_literal_helper( self, string, *, quote_types=_ALL_QUOTES, escape_special_whitespace=False ): """Helper for writing string literals, minimizing escapes. Returns the tuple (string literal to write, possible quote types). """ def escape_char(c): # \n and \t are non-printable, but we only escape them if # escape_special_whitespace is True if not escape_special_whitespace and c in "\n\t": return c # Always escape backslashes and other non-printable characters if c == "\\" or not c.isprintable(): return c.encode("unicode_escape").decode("ascii") return c escaped_string = "".join(map(escape_char, string)) possible_quotes = quote_types if "\n" in escaped_string: possible_quotes = [q for q in possible_quotes if q in _MULTI_QUOTES] possible_quotes = [q for q in possible_quotes if q not in escaped_string] if not possible_quotes: # If there aren't any possible_quotes, fallback to using repr # on the original string. Try to use a quote from quote_types, # e.g., so that we use triple quotes for docstrings. string = repr(string) quote = next((q for q in quote_types if string[0] in q), string[0]) return string[1:-1], [quote] if escaped_string: # Sort so that we prefer '''"''' over """\"""" possible_quotes.sort(key=lambda q: q[0] == escaped_string[-1]) # If we're using triple quotes and we'd need to escape a final # quote, escape it if possible_quotes[0][0] == escaped_string[-1]: assert len(possible_quotes[0]) == 3 escaped_string = escaped_string[:-1] + "\\" + escaped_string[-1] return escaped_string, possible_quotes def _write_str_avoiding_backslashes(self, string, *, quote_types=_ALL_QUOTES): """Write string literal value with a best effort attempt to avoid backslashes.""" string, quote_types = self._str_literal_helper(string, quote_types=quote_types) quote_type = quote_types[0] self.write(f"{quote_type}{string}{quote_type}") def visit_JoinedStr(self, node): self.write("f") if self._avoid_backslashes: self._fstring_JoinedStr(node, self.buffer_writer) self._write_str_avoiding_backslashes(self.buffer) return # If we don't need to avoid backslashes globally (i.e., we only need # to avoid them inside FormattedValues), it's cosmetically preferred # to use escaped whitespace. That is, it's preferred to use backslashes # for cases like: f"{x}\n". To accomplish this, we keep track of what # in our buffer corresponds to FormattedValues and what corresponds to # Constant parts of the f-string, and allow escapes accordingly. buffer = [] for value in node.values: meth = getattr(self, "_fstring_" + type(value).__name__) meth(value, self.buffer_writer) buffer.append((self.buffer, isinstance(value, Constant))) new_buffer = [] quote_types = _ALL_QUOTES for value, is_constant in buffer: # Repeatedly narrow down the list of possible quote_types value, quote_types = self._str_literal_helper( value, quote_types=quote_types, escape_special_whitespace=is_constant ) new_buffer.append(value) value = "".join(new_buffer) quote_type = quote_types[0] self.write(f"{quote_type}{value}{quote_type}") def visit_FormattedValue(self, node): self.write("f") self._fstring_FormattedValue(node, self.buffer_writer) self._write_str_avoiding_backslashes(self.buffer) def _fstring_JoinedStr(self, node, write): for value in node.values: meth = getattr(self, "_fstring_" + type(value).__name__) meth(value, write) def _fstring_Constant(self, node, write): if not isinstance(node.value, str): raise ValueError("Constants inside JoinedStr should be a string.") value = node.value.replace("{", "{{").replace("}", "}}") write(value) def _fstring_FormattedValue(self, node, write): write("{") unparser = type(self)(_avoid_backslashes=True) unparser.set_precedence(_Precedence.TEST.next(), node.value) expr = unparser.visit(node.value) if expr.startswith("{"): write(" ") # Separate pair of opening brackets as "{ {" if "\\" in expr: raise ValueError("Unable to avoid backslash in f-string expression part") write(expr) if node.conversion != -1: conversion = chr(node.conversion) if conversion not in "sra": raise ValueError("Unknown f-string conversion.") write(f"!{conversion}") if node.format_spec: write(":") meth = getattr(self, "_fstring_" + type(node.format_spec).__name__) meth(node.format_spec, write) write("}") def visit_Name(self, node): self.write(node.id) def _write_docstring(self, node): self.fill() if node.kind == "u": self.write("u") self._write_str_avoiding_backslashes(node.value, quote_types=_MULTI_QUOTES) def _write_constant(self, value): if isinstance(value, (float, complex)): # Substitute overflowing decimal literal for AST infinities, # and inf - inf for NaNs. self.write( repr(value) .replace("inf", _INFSTR) .replace("nan", f"({_INFSTR}-{_INFSTR})") ) elif self._avoid_backslashes and isinstance(value, str): self._write_str_avoiding_backslashes(value) else: self.write(repr(value)) def visit_Constant(self, node): value = node.value if isinstance(value, tuple): with self.delimit("(", ")"): self.items_view(self._write_constant, value) elif value is ...: self.write("...") else: if node.kind == "u": self.write("u") self._write_constant(node.value) def visit_List(self, node): with self.delimit("[", "]"): self.interleave(lambda: self.write(", "), self.traverse, node.elts) def visit_ListComp(self, node): with self.delimit("[", "]"): self.traverse(node.elt) for gen in node.generators: self.traverse(gen) def visit_GeneratorExp(self, node): with self.delimit("(", ")"): self.traverse(node.elt) for gen in node.generators: self.traverse(gen) def visit_SetComp(self, node): with self.delimit("{", "}"): self.traverse(node.elt) for gen in node.generators: self.traverse(gen) def visit_DictComp(self, node): with self.delimit("{", "}"): self.traverse(node.key) self.write(": ") self.traverse(node.value) for gen in node.generators: self.traverse(gen) def visit_comprehension(self, node): if node.is_async: self.write(" async for ") else: self.write(" for ") self.set_precedence(_Precedence.TUPLE, node.target) self.traverse(node.target) self.write(" in ") self.set_precedence(_Precedence.TEST.next(), node.iter, *node.ifs) self.traverse(node.iter) for if_clause in node.ifs: self.write(" if ") self.traverse(if_clause) def visit_IfExp(self, node): with self.require_parens(_Precedence.TEST, node): self.set_precedence(_Precedence.TEST.next(), node.body, node.test) self.traverse(node.body) self.write(" if ") self.traverse(node.test) self.write(" else ") self.set_precedence(_Precedence.TEST, node.orelse) self.traverse(node.orelse) def visit_Set(self, node): if node.elts: with self.delimit("{", "}"): self.interleave(lambda: self.write(", "), self.traverse, node.elts) else: # `{}` would be interpreted as a dictionary literal, and # `set` might be shadowed. Thus: self.write('{*()}') def visit_Dict(self, node): def write_key_value_pair(k, v): self.traverse(k) self.write(": ") self.traverse(v) def write_item(item): k, v = item if k is None: # for dictionary unpacking operator in dicts {**{'y': 2}} # see PEP 448 for details self.write("**") self.set_precedence(_Precedence.EXPR, v) self.traverse(v) else: write_key_value_pair(k, v) with self.delimit("{", "}"): self.interleave( lambda: self.write(", "), write_item, zip(node.keys, node.values) ) def visit_Tuple(self, node): with self.delimit("(", ")"): self.items_view(self.traverse, node.elts) unop = {"Invert": "~", "Not": "not", "UAdd": "+", "USub": "-"} unop_precedence = { "not": _Precedence.NOT, "~": _Precedence.FACTOR, "+": _Precedence.FACTOR, "-": _Precedence.FACTOR, } def visit_UnaryOp(self, node): operator = self.unop[node.op.__class__.__name__] operator_precedence = self.unop_precedence[operator] with self.require_parens(operator_precedence, node): self.write(operator) # factor prefixes (+, -, ~) shouldn't be seperated # from the value they belong, (e.g: +1 instead of + 1) if operator_precedence is not _Precedence.FACTOR: self.write(" ") self.set_precedence(operator_precedence, node.operand) self.traverse(node.operand) binop = { "Add": "+", "Sub": "-", "Mult": "*", "MatMult": "@", "Div": "/", "Mod": "%", "LShift": "<<", "RShift": ">>", "BitOr": "|", "BitXor": "^", "BitAnd": "&", "FloorDiv": "//", "Pow": "**", } binop_precedence = { "+": _Precedence.ARITH, "-": _Precedence.ARITH, "*": _Precedence.TERM, "@": _Precedence.TERM, "/": _Precedence.TERM, "%": _Precedence.TERM, "<<": _Precedence.SHIFT, ">>": _Precedence.SHIFT, "|": _Precedence.BOR, "^": _Precedence.BXOR, "&": _Precedence.BAND, "//": _Precedence.TERM, "**": _Precedence.POWER, } binop_rassoc = frozenset(("**",)) def visit_BinOp(self, node): operator = self.binop[node.op.__class__.__name__] operator_precedence = self.binop_precedence[operator] with self.require_parens(operator_precedence, node): if operator in self.binop_rassoc: left_precedence = operator_precedence.next() right_precedence = operator_precedence else: left_precedence = operator_precedence right_precedence = operator_precedence.next() self.set_precedence(left_precedence, node.left) self.traverse(node.left) self.write(f" {operator} ") self.set_precedence(right_precedence, node.right) self.traverse(node.right) cmpops = { "Eq": "==", "NotEq": "!=", "Lt": "<", "LtE": "<=", "Gt": ">", "GtE": ">=", "Is": "is", "IsNot": "is not", "In": "in", "NotIn": "not in", } def visit_Compare(self, node): with self.require_parens(_Precedence.CMP, node): self.set_precedence(_Precedence.CMP.next(), node.left, *node.comparators) self.traverse(node.left) for o, e in zip(node.ops, node.comparators): self.write(" " + self.cmpops[o.__class__.__name__] + " ") self.traverse(e) boolops = {"And": "and", "Or": "or"} boolop_precedence = {"and": _Precedence.AND, "or": _Precedence.OR} def visit_BoolOp(self, node): operator = self.boolops[node.op.__class__.__name__] operator_precedence = self.boolop_precedence[operator] def increasing_level_traverse(node): nonlocal operator_precedence operator_precedence = operator_precedence.next() self.set_precedence(operator_precedence, node) self.traverse(node) with self.require_parens(operator_precedence, node): s = f" {operator} " self.interleave(lambda: self.write(s), increasing_level_traverse, node.values) def visit_Attribute(self, node): self.set_precedence(_Precedence.ATOM, node.value) self.traverse(node.value) # Special case: 3.__abs__() is a syntax error, so if node.value # is an integer literal then we need to either parenthesize # it or add an extra space to get 3 .__abs__(). if isinstance(node.value, Constant) and isinstance(node.value.value, int): self.write(" ") self.write(".") self.write(node.attr) def visit_Call(self, node): self.set_precedence(_Precedence.ATOM, node.func) self.traverse(node.func) with self.delimit("(", ")"): comma = False for e in node.args: if comma: self.write(", ") else: comma = True self.traverse(e) for e in node.keywords: if comma: self.write(", ") else: comma = True self.traverse(e) def visit_Subscript(self, node): def is_simple_tuple(slice_value): # when unparsing a non-empty tuple, the parentheses can be safely # omitted if there aren't any elements that explicitly requires # parentheses (such as starred expressions). return ( isinstance(slice_value, Tuple) and slice_value.elts and not any(isinstance(elt, Starred) for elt in slice_value.elts) ) self.set_precedence(_Precedence.ATOM, node.value) self.traverse(node.value) with self.delimit("[", "]"): if is_simple_tuple(node.slice): self.items_view(self.traverse, node.slice.elts) else: self.traverse(node.slice) def visit_Starred(self, node): self.write("*") self.set_precedence(_Precedence.EXPR, node.value) self.traverse(node.value) def visit_Ellipsis(self, node): self.write("...") def visit_Slice(self, node): if node.lower: self.traverse(node.lower) self.write(":") if node.upper: self.traverse(node.upper) if node.step: self.write(":") self.traverse(node.step) def visit_arg(self, node): self.write(node.arg) if node.annotation: self.write(": ") self.traverse(node.annotation) def visit_arguments(self, node): first = True # normal arguments all_args = node.posonlyargs + node.args defaults = [None] * (len(all_args) - len(node.defaults)) + node.defaults for index, elements in enumerate(zip(all_args, defaults), 1): a, d = elements if first: first = False else: self.write(", ") self.traverse(a) if d: self.write("=") self.traverse(d) if index == len(node.posonlyargs): self.write(", /") # varargs, or bare '*' if no varargs but keyword-only arguments present if node.vararg or node.kwonlyargs: if first: first = False else: self.write(", ") self.write("*") if node.vararg: self.write(node.vararg.arg) if node.vararg.annotation: self.write(": ") self.traverse(node.vararg.annotation) # keyword-only arguments if node.kwonlyargs: for a, d in zip(node.kwonlyargs, node.kw_defaults): self.write(", ") self.traverse(a) if d: self.write("=") self.traverse(d) # kwargs if node.kwarg: if first: first = False else: self.write(", ") self.write("**" + node.kwarg.arg) if node.kwarg.annotation: self.write(": ") self.traverse(node.kwarg.annotation) def visit_keyword(self, node): if node.arg is None: self.write("**") else: self.write(node.arg) self.write("=") self.traverse(node.value) def visit_Lambda(self, node): with self.require_parens(_Precedence.TEST, node): self.write("lambda ") self.traverse(node.args) self.write(": ") self.set_precedence(_Precedence.TEST, node.body) self.traverse(node.body) def visit_alias(self, node): self.write(node.name) if node.asname: self.write(" as " + node.asname) def visit_withitem(self, node): self.traverse(node.context_expr) if node.optional_vars: self.write(" as ") self.traverse(node.optional_vars) def unparse(ast_obj): unparser = _Unparser() return unparser.visit(ast_obj) def main(): import argparse parser = argparse.ArgumentParser(prog='python -m ast') parser.add_argument('infile', type=argparse.FileType(mode='rb'), nargs='?', default='-', help='the file to parse; defaults to stdin') parser.add_argument('-m', '--mode', default='exec', choices=('exec', 'single', 'eval', 'func_type'), help='specify what kind of code must be parsed') parser.add_argument('--no-type-comments', default=True, action='store_false', help="don't add information about type comments") parser.add_argument('-a', '--include-attributes', action='store_true', help='include attributes such as line numbers and ' 'column offsets') parser.add_argument('-i', '--indent', type=int, default=3, help='indentation of nodes (number of spaces)') args = parser.parse_args() with args.infile as infile: source = infile.read() tree = parse(source, args.infile.name, args.mode, type_comments=args.no_type_comments) print(dump(tree, include_attributes=args.include_attributes, indent=args.indent)) if __name__ == '__main__': main()