I've noticed with latest python 3.1 checkout (68631) if I have this
object hierarchy with a default __init__ in the superclass to be used
by the subclasses which don't necessarily need an __init__ it blows up
with a TypeError.
class Field(object):
def __init__(self, data):
"""Default init for the subclasses"""
print("init class=%r, self=%r" % (self.__class__.__name__, self))
super(Field, self).__init__(data)
self.data = self.orig = data
class IntegerField(Field):
def __init__(self, data):
"""Overridden init"""
super(IntegerField, self).__init__(data)
self.data = int(data)
class StringField(Field):
pass
f1 = StringField('abc')
f2 = IntegerField('10')
print("f1=%r" % f1.data)
print("f2=%r" % f2.data)
print(type(f1))
print(type(f2))
It blows up with
init class='StringField', self=<__main__.StringField object at 0xb7d47b4c>
Traceback (most recent call last):
File "subclass-super-problem-py3k.py", line 17, in <module>
f1 = StringField('abc')
File "subclass-super-problem-py3k.py", line 5, in __init__
super(Field, self).__init__(data)
TypeError: object.__init__() takes no parameters
The exact same code runs under py 2.5 just fine.
I can't think of anything to write in Field.__init__ to tell whether
super is about to run __init__ on object.
The problem can be fixed (inelegantly IMHO) like this
class BaseField(object):
def __init__(self, data):
"""Default init for the subclasses"""
self.data = self.orig = data
class Field(BaseField):
def __init__(self, data):
"""Another Default init for the subclasses"""
super(Field, self).__init__(data)
class IntegerField(Field):
def __init__(self, data):
"""Overridden init"""
super(IntegerField, self).__init__(data)
self.data = int(data)
class StringField(Field):
pass
f1 = StringField('abc')
f2 = IntegerField('10')
print("f1=%r" % f1.data)
print("f2=%r" % f2.data)
print(type(f1))
print(type(f2))
Is this a bug or a feature? Is there a better work-around?
--
Nick Craig-Wood <n...@craig-wood.com> -- http://www.craig-wood.com/nick
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