def _convert_num(node):
        if isinstance(node, Constant):
            if type(node.value) in (int, float, complex):
                return node.value
>       raise ValueError('malformed node or string: ' + repr(node))
E       ValueError: malformed node or string: <_ast.Name object at 0x7f0e7ebab320>

When a malformed node passes into literal_eval, it raises ValueError with repr of node (which is just a memory address and type). I think using dump(node) at there is a better option, like

node = <_ast.Name object at 0x7fa8279847d0>

    def _convert_num(node):
        if isinstance(node, Constant):
            if type(node.value) in (int, float, complex):
                return node.value
>       raise ValueError('malformed node or string: ' + dump(node))
E       ValueError: malformed node or string: Name(id='a', ctx=Load())