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gh-124503: simplified ast.literal_eval #137010

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gh-124503: simplified ast.literal_eval #137010

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97 changes: 52 additions & 45 deletions Lib/ast.py
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Original file line number Diff line number Diff line change
Expand Up @@ -57,53 +57,60 @@ def literal_eval(node_or_string):
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 = parse(node_or_string.lstrip(" \t"), mode='eval').body
elif 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 _convert_literal(node_or_string)


def _convert_literal(node):
"""
Used by `literal_eval` to convert an AST node into a value.
"""
if isinstance(node, Constant):
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)
if isinstance(node, Dict) and len(node.keys) == len(node.values):
return dict(zip(
map(_convert_literal, node.keys),
map(_convert_literal, node.values),
))
if isinstance(node, Tuple):
return tuple(map(_convert_literal, node.elts))
if isinstance(node, List):
return list(map(_convert_literal, node.elts))
if isinstance(node, Set):
return set(map(_convert_literal, node.elts))
if (
isinstance(node, Call) and isinstance(node.func, Name)
and node.func.id == 'set' and node.args == node.keywords == []
):
return set()
if (
isinstance(node, UnaryOp)
and isinstance(node.op, (UAdd, USub))
and isinstance(node.operand, Constant)
and type(operand := node.operand.value) in (int, float, complex)
):
if isinstance(node.op, UAdd):
return + operand
else:
return - operand
if (
isinstance(node, BinOp)
and isinstance(node.op, (Add, Sub))
and isinstance(node.left, (Constant, UnaryOp))
and isinstance(node.right, Constant)
and type(left := _convert_literal(node.left)) in (int, float)
and type(right := _convert_literal(node.right)) is complex
):
if isinstance(node.op, Add):
return left + right
else:
return left - right
msg = "malformed node or string"
if lno := getattr(node, 'lineno', None):
msg += f' on line {lno}'
raise ValueError(msg + f': {node!r}')


def dump(
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