Question

I know that comparison of types is not recommended, but I have some code that does this in an if elif series. However, I am confused as to how None values work.

def foo(object)
    otype = type(object)
    #if otype is None: # this doesn't work
    if object is None: # this works fine
        print("yep")
    elif otype is int:
    elif ...

How come I can compare just fine with is int and so forth, but not with is None? types.NoneType seems to be gone in Python 3.2, so I can’t use that…

The following

i = 1
print(i)
print(type(i))
print(i is None)
print(type(i) is int)

prints

1
<class 'int'>
False
True

whereas

i = None
print(i)
print(type(i))
print(i is None)
print(type(i) is None)

prints

None
<class 'NoneType'>
True
False

I guess None is special, but what gives? Does NoneType actually exist, or is Python lying to me?

Answer 1

None is a special-case singleton provided by Python. NoneType is the type of the singleton object. type(i) is None is False, but type(i) is type(None) should be true.