pythonhashset

Any reason there is no returned value from `set.add`?

Current, since the returned value from set.add is always None. I have to do the following.

if 1 in s:
    print 'already found'
    return
s.add(1)

Would it be nice if I can

if not s.add(1):
    print 'already found'
    return
Solution 
  • >>> None == False
False
>>> None == True
False
>>> None == None
True
>>> not None
True

    If s.add always returns None, then your condition will always be True. But since s is a set, just add the value to it. You can't have duplicate values in a set, by definition :

    >>> a = set()
>>> a.add(1)
>>> a
{1}
>>> a.add(1)
>>> a
{1}

    If you just want to know if 1 is in the set, then do if 1 in s.