ValueError: malformed string when using ast.literal_eval

Question

It is widely known that using eval() is a potential security risk so the use of ast.literal_eval(node_or_string) is promoted

However In python 2.7 it re

Answer 1

Use the source, luke!

http://hg.python.org/cpython/file/2.7/Lib/ast.py#l40 http://hg.python.org/cpython/file/3.2/Lib/ast.py#l39

You will find your answer in there. Specifically, the 2.7 version has the weird restriction on line 70 that the right node of the BinOp is complex.

>>> sys.version
'2.7.3 (default, Sep 26 2013, 20:03:06) \n[GCC 4.6.3]'
>>> ast.literal_eval('9 + 0j')
(9 + 0j)
>>> ast.literal_eval('0j + 9')
ValueError: malformed string

I'm guessing that the intention of 2.7 was to allow literal_eval of complex literals for example numbers like 9 + 0j, and it was never intended to do simple integer additions. Then in python 3 they beefed up the literal_eval to handle these cases.