In Python, if auth_user_id is not None, fails to match None?

Question

How do I stop my code from executing when a variable is None? I have tried many things. Here is my current incarnation:

post_body = request.POST
auth_user_id = post_body.get("auth_user_id", None)

if auth_user_id is not None:
    print(auth_user_id)
    search_user = SearchUser.objects.get(user_id=auth_user_id)

Right now this code dies on the last line with this error:

ValueError: invalid literal for int() with base 10: 'None'

And this:

        print(auth_user_id)

Shows me "None".

So what is going on? How do I stop the code on None?

Answer 1

Obviously what you get here is the literal string 'None', not the None object - note how the error messages differ, when passing None you get a TypeError, when passing 'None' you get a ValueError:

# py2.7

>>> int(None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: int() argument must be a string or a number, not 'NoneType'
>>> int('None')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: 'None'


# py3
>>> int(None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: int() argument must be a string, a bytes-like object or a number, not 'NoneType'
>>> int('None')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: 'None'

Your problem comes from the HTTP request body (since it's a POST) containing the literal string 'None' for the "auth_user_id" key. Note that using a Django Form with proper validation would avoid the problem.