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up vote 0 down vote favorite

I am writing some sort of simple web-interpreter for vk.com . I look for messages, check if they are valid Python code, and then I want to execute that code, and return any stdout to code sender. I have implemented anything but code checker.

import ast

def is_valid(code): 
    try:
        ast.parse(code)
    except SyntaxError:
        print('Input isnt code.')
        return False
    print('Code is ok.')
    return True

is_valid() always return True regardless of what comes in. Im really confused...

share|improve this question
    
Can you give an example of non-code that returns True. – AChampion 18 hours ago
    
>>> is_valid('test') Code is ok. True – MaxLunar 18 hours ago
4  
That's valid code - an identifier. – AChampion 18 hours ago
up vote 1 down vote accepted

Keep in mind, the difference between a runtime error and a parser error is significant in your case and example. The statement:

test

is valid code. Even though this statement will throw a NameError when the Python VM executes the code, the parser will not know that it actually wasn't assigned a value before the statement is parsed, so that's why it's a runtime error, and not a syntax error.

share|improve this answer
    
Thanks! Ill fix it by throwing NameError then – MaxLunar 18 hours ago
1  
@MaxLunar you can't throw a NameError, because how would you know that the user's code is using a variable that wasn't assigned a value? – self 18 hours ago
    
@MaxLunar I think you have a misunderstanding here. Is x + 1 valid code? – Noufal Ibrahim 18 hours ago
    
Hm, If i send message that tell user that his variable wasnt defined yet if NameError is raised... – MaxLunar 18 hours ago
    
@Noufal Ibrahim x + 1 is valid code – MaxLunar 18 hours ago

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