multiple inharitance super() question

[Alex Greif]

Hi,

Before 2.2 I could initialize multiple super classes like this:
class B(A,AA):
def __init__(self, args):
A.__init__(self,args)
AA.__init__(self,args)

Tutorials say that since python 2.2 superclasses should be initialized
with the super() construct.

class A(object):
def __init__(self, args):
...

class B(A):
def __init__(self, args):
super(B, self).__init__(args)


BUT what happens if B extends from A and AA like:

class A(object):
def __init__(self, args):
...

class AA(object):
def __init__(self, args):
...

class B(A,AA):
def __init__(self, args):
super(B, self).__init__(args)


How can I tell that B.__init__() should initialize A and AA?
Or is the new super() so clever to call A.__init__() and AA.__init__()
internally?

thanks,
Alex Greif


________________________________________
http://www.fotobuch-xxl.de/

 

[Peter Otten]

BUT what happens if B extends from A and AA like:

class A(object):
def __init__(self, args):
...

class AA(object):
def __init__(self, args):
...

class B(A,AA):
def __init__(self, args):
super(B, self).__init__(args)


How can I tell that B.__init__() should initialize A and AA?
Or is the new super() so clever to call A.__init__() and AA.__init__()
internally?

Yes but only if you put a super() call into A/AA.__init__().

class A(object):
def __init__(self, args):
print "init A"
super(A, self).__init__(args)

class AA(object):
def __init__(self, args):
print "init AA"
super(AA, self).__init__(args)


class B(A, AA):
def __init__(self, args):
print "init B"
super(B, self).__init__(args)

if __name__ == "__main__":
B(42)

The most significant constraint of that layout is that all __init__()
methods need compatible signatures.
Of course explicit invocation of baseclass initializers will continue to
work...

Peter