Python: self.class vs. type(self)

Question

I’m wondering if there is a difference between

class Test(object):
    def __init__(self):
        print self.__class__.__name__

and

class Test(object):
    def __init__(self):
        print type(self).__name__

?

Is there a reason to prefer one or the other?

(In my use case I want to use it to determine the logger name, but I guess this doesn’t matter)

Asked By: Martin Schulze

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Source

Answer 1

As far as I am aware, the latter is just a nicer way of doing the former.

It’s actually not that unusual in Python, consider repr(x), which just calls x.__repr__() or len(x), which just calls x.__len__(). Python prefers to use built-ins for common functions that you are likely to use over a range of classes, and generally implements these by calling __x__() methods.

Answered By: Gareth Latty

Answer 2

>>> class Test(object): pass
>>> t = Test()
>>> type(t) is t.__class__
True
>>> type(t)
__main__.Test

So those two are the same. ~~I would use self.__class__ since it’s more obvious what it is.~~

However, type(t) won’t work for old-style classes since the type of an instance of an old-style class is instance while the type of a new-style class instance is its class:

>>> class Test(): pass
>>> t = Test()
>>> type(t) is t.__class__
False
>>> type(t)
instance

Answered By: ThiefMaster

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