Question

Is this just two ways to write the same code? Is there any functional difference I should be aware of?

>>> a = 'foo'
>>> if not a == 'bar':
...     'its not'
... 
'its not'
>>> if a != 'bar':
...     'its not'
... 
'its not'

Answer 1

In python, to check whether or not an object is equal or not equal to another object, special functions are called. __eq__ is called to check ==, while __ne__ is called to check !=

In general, an object could define __ne__ differently than __eq__.

E.g.

class Junk(object):
    def __ne__(self, other):
        return False

    def __eq__(self, other):
        return False

j = Junk()
print not j == 1
print j != 1

This yields:

True
False

However, this would be especially evil… You usually should never have to worry about this.