1 # -*- coding: utf-8 -*-
2 """ Backport of Python 2.6's ast.py for Python 2.5
4 __all__ = ['literal_eval']
6 from ast import literal_eval
9 from _ast import __version__
12 def parse(expr, filename='<unknown>', mode='exec'):
14 Parse an expression into an AST node.
15 Equivalent to compile(expr, filename, mode, PyCF_ONLY_AST).
17 return compile(expr, filename, mode, PyCF_ONLY_AST)
20 def literal_eval(node_or_string):
22 Safely evaluate an expression node or a string containing a Python
23 expression. The string or node provided may only consist of the
24 following Python literal structures: strings, numbers, tuples, lists,
25 dicts, booleans, and None.
27 _safe_names = {'None': None, 'True': True, 'False': False}
28 if isinstance(node_or_string, basestring):
29 node_or_string = parse(node_or_string, mode='eval')
30 if isinstance(node_or_string, Expression):
31 node_or_string = node_or_string.body
33 if isinstance(node, Str):
35 elif isinstance(node, Num):
37 elif isinstance(node, Tuple):
38 return tuple(map(_convert, node.elts))
39 elif isinstance(node, List):
40 return list(map(_convert, node.elts))
41 elif isinstance(node, Dict):
42 return dict((_convert(k), _convert(v)) for k, v
43 in zip(node.keys, node.values))
44 elif isinstance(node, Name):
45 if node.id in _safe_names:
46 return _safe_names[node.id]
47 raise ValueError('malformed string')
48 return _convert(node_or_string)