Subclasses in Python

[Peter Otten]

Thomas Philips wrote:

> I followed Shalabh's suggestion and rewrote Alien as a subclass of
> Player, and used self.__Class__.<whatever I need to access> to access
> the class attributes in the class and subclass. Works like a charm,
> but I'm having some difficulty printing class names. I want
> self.__class__ to return just the name of the class without some
> ancillary stuff thrown in. A snippet of code follows:
> 
> class Player(object):
>     #Class attributes for class Player
>     threshold = 50
>     initial_strength=100
>     n=0
> 
>     #Private methods for class Player
>     def __init__(self,name):
>         self.name = name
>         self.strength = self.__class__.initial_strength
>         self.__class__.n +=1
>         print self.__class__

make that
          print self.__class__.__name__
          
> class Alien(Player):
>     #Class attributes for subclass Alien
>     threshold = 30
>     initial_strength=150
>     n=0
> 
> When a new object is instantiated, the print statement in __init__
> gives me
> <class '__main__.Player'>
> or
> <class '__main__.Alien'>
> How can I just get it to return
> 
> Player
> or
> Alien
> 
> Interestingly, if I do a class comparison of the form
> 
> if self.__class__== Alien:

This compares two *classes* not classnames. Even classes with the same name 
defined, say, in a function would be recognized as not equal:

>>> def makeClass():
...     class A(object): pass
...     return A
...
>>> A1 = makeClass()
>>> A2 = makeClass()
>>> A1
<class '__main__.A'>
>>> A2
<class '__main__.A'>
>>> A1 == A2
False

Now compare the names:

>>> A1.__name__, A2.__name__
('A', 'A')
>>> A1.__name__ == A2.__name__
True
>>>

>     foo
> elif self.__class__== Player
>     bar
> 
> The comparison proceeds correctly. How can I get it to print the class
> name cleanly? Do I have to convert <class '__main__.Alien'> to a
> string and then use one or more string functions to clean it up?

No, "<class '__main__.Alien'>" is the string that is generated when the
class Alien is converted to string. If you want something else you have to
change to a custom metaclass - better stick to Alien.__name__.

Peter