Inconsistency in Python programming language?

[Gribouillis]

Here is a new version. You don't need to import the io module.

def func(s):
    t = re.sub(r'\s+', '', s)
    sign = True
    for tok in generate_tokens(iter([t, '']).__next__):
        if sign and tok[1] in ('-', '+'):
            sign = False
            continue
        if tok[0] == NUMBER:
            return ast.literal_eval(t[:tok[3][1]])
        return 0
    return 0

If there is still an error, please give full bug report!