gclient_eval.py 文件源码

def _gclient_eval(node_or_string, global_scope, filename='<unknown>'):
  """Safely evaluates a single expression. Returns the result."""
  _allowed_names = {'None': None, 'True': True, 'False': False}
  if isinstance(node_or_string, basestring):
    node_or_string = ast.parse(node_or_string, filename=filename, mode='eval')
  if isinstance(node_or_string, ast.Expression):
    node_or_string = node_or_string.body
  def _convert(node):
    if isinstance(node, ast.Str):
      return node.s
    elif isinstance(node, ast.Num):
      return node.n
    elif isinstance(node, ast.Tuple):
      return tuple(map(_convert, node.elts))
    elif isinstance(node, ast.List):
      return list(map(_convert, node.elts))
    elif isinstance(node, ast.Dict):
      return collections.OrderedDict(
          (_convert(k), _convert(v))
          for k, v in zip(node.keys, node.values))
    elif isinstance(node, ast.Name):
      if node.id not in _allowed_names:
        raise ValueError(
            'invalid name %r (file %r, line %s)' % (
                node.id, filename, getattr(node, 'lineno', '<unknown>')))
      return _allowed_names[node.id]
    elif isinstance(node, ast.Call):
      if not isinstance(node.func, ast.Name):
        raise ValueError(
            'invalid call: func should be a name (file %r, line %s)' % (
                filename, getattr(node, 'lineno', '<unknown>')))
      if node.keywords or node.starargs or node.kwargs:
        raise ValueError(
            'invalid call: use only regular args (file %r, line %s)' % (
                filename, getattr(node, 'lineno', '<unknown>')))
      args = map(_convert, node.args)
      return global_scope[node.func.id](*args)
    elif isinstance(node, ast.BinOp) and isinstance(node.op, ast.Add):
      return _convert(node.left) + _convert(node.right)
    elif isinstance(node, ast.BinOp) and isinstance(node.op, ast.Mod):
      return _convert(node.left) % _convert(node.right)
    else:
      raise ValueError(
          'unexpected AST node: %s %s (file %r, line %s)' % (
              node, ast.dump(node), filename,
              getattr(node, 'lineno', '<unknown>')))
  return _convert(node_or_string)