ast.literal_eval() throws an error when passed parameter evaluated to be a normal string

Question

I have a python function to which a string is passed as parameter, the parameter may be a string representation of int, array,dictionary or a normal string

for int,array and dictionary its working properly, but if the parameter is a normal string the ast.literal_eval() throws error

import ast # below statements throw error #output_value = ast.literal_eval('someNormalString') #output_value = ast.literal_eval('name1 name2 name3') #below statements work fine output_value = ast.literal_eval('5') output_value = ast.literal_eval('[{"id":"XYZ_GTTC_TYR", "name":"Suction"}]') output_value = ast.literal_eval('["name1","name2"]') print(output_value)

is there any way to to handle it if the param is just a normal string?

below is my python function

def func(key): value = ast.literal_eval(value) return value

You should preferably know whether your value is supposed to represent something that can be eval'd or not. What if you have a string that looks like a valid literal, but is supposed to be a plain string? — deceze
– deceze ♦, Commented Jun 10, 2021 at 9:24
Side note: those are valid list and dictionary literals, but they also happen to be valid JSON. Are you sure JSON isn't what you need to be using? — Alex Hall
– Alex Hall, Commented Jun 10, 2021 at 10:22

Seon · Accepted Answer · 2021-06-10 09:26:01Z

A good way to understand what's happening here is to think of ast.literal_eval as a (highly simplified) python interpreter, which evaluates what's inside the string.

When you run ast.literal_eval('someNormalString'), it's as if you told python to evaluate someNormalString - which obviosuly raises an error.

Try: ast.literal_eval("'someNormalString'") so ast is evaluating 'someNormalString' instead.

Tom McLean · Accepted Answer · 2021-06-10 09:24:33Z

The code is viewing the string as someNormalString but it actually needs to use 'someNormalString'. To achieve this, alter the code like so:

output_value = ast.literal_eval("'someNormalString'") output_value = ast.literal_eval("'name1 name2 name3'")

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