Why does this string not work with ast.literal_eval

Question

I get a malformed string error.

Here is my testings

>>> eval("'Hello:: '+'fdsfds'")
'Hello:: fdsfds'
>>> import ast
>>> ast.literal_eval("'Hello:: '+'fdsfds'")
Traceback (most recent call last):
  File "<pyshell#4>", line 1, in <module>
    ast.literal_eval("'Hello:: '+'fdsfds'")
  File "C:\Python27\lib\ast.py", line 80, in literal_eval
    return _convert(node_or_string)
  File "C:\Python27\lib\ast.py", line 79, in _convert
    raise ValueError('malformed string')
ValueError: malformed string

I think ast checks if it can be exec'd ... – Joran Beasley Aug 22 '12 at 19:38 — Joran Beasley, Aug 22 '12 at 19:38

score 8 · Accepted Answer · answered Aug 22 '12 at 19:38

8

From the ast.literal_eval docs:

The string or node provided may only consist of the following Python literal structures: strings, numbers, tuples, lists, dicts, booleans, and None.

Concatenation using + isn't included within that: it's not a literal expression, it's a call to str.__add__. It's the same reason 1+1 or "hello".upper() wouldn't work.

answered Aug 22 '12 at 19:38

David Robinson

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So basically `literal_eval` is utterly useless. – Thomas Dec 30 '13 at 05:06
simple ast.literal_eval("randomalphabets") also throws "malformed node or string: " error, with Python 3.9.2. – ramputan Mar 09 '21 at 13:26

Why does this string not work with ast.literal_eval

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