Re: [Tutor] problem with a sub-class
On 30/11/2017 22:08, Alan Gauld via Tutor wrote: On 30/11/17 15:37, Shall, Sydney wrote: My problem is with constructing a sub-class. My sub-class is constructed as follows: import Population_ProductivityV24 as POCWP Note that POCWP is an alias for the *module* Population_ProductivityV24. It is not a class. line 27 : class SimulateCycleZero(POCWP): Here you define a class that subclasses your imported module. Frankly I'm surprised that you don't get an error there but hey... line 28 : def __init__(self, dirname_p): But this is now an init for a subclass of module. The error message is as follows: File "/Users/sydney/AnacondaProjects/Capital/Capital_with_productivity/Current_Versions/Simulate_Cycle_Zero_V3.py", line 27, in class SimulateCycleZero(POCWP): TypeError: module.__init__() takes at most 2 arguments (3 given) So I'm guessing the use of a module to subclass has confused things and I confess I'm not clear on exactly what is going on and why you get this message. But I'm pretty sure you don;t want to subclass your imported module and thats the mistake. Thanks to Alan and Peter for explaining sub-classing to me. I understand a bit better now. My program is corrected and does not give the error any more. -- Sydney ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] problem with a sub-class
Alan Gauld via Tutor wrote:
> On 30/11/17 15:37, Shall, Sydney wrote:
>
>> My problem is with constructing a sub-class.
>>
>> My sub-class is constructed as follows:
>>
>> import Population_ProductivityV24 as POCWP
>
> Note that POCWP is an alias for the *module* Population_ProductivityV24.
> It is not a class.
>
>> line 27 : class SimulateCycleZero(POCWP):
>
> Here you define a class that subclasses your imported module.
> Frankly I'm surprised that you don't get an error there
> but hey...
>
>> line 28 : def __init__(self, dirname_p):
>
> But this is now an init for a subclass of module.
>
>> The error message is as follows:
>>
>>File
>>
"/Users/sydney/AnacondaProjects/Capital/Capital_with_productivity/Current_Versions/Simulate_Cycle_Zero_V3.py",
>> line 27, in
>> class SimulateCycleZero(POCWP):
>>
>> TypeError: module.__init__() takes at most 2 arguments (3 given)
>
> So I'm guessing the use of a module to subclass
> has confused things and I confess I'm not clear on
> exactly what is going on and why you get this message.
A class is an instance of its metaclass.
class A:
pass
is roughly equivalent to
A = type("A", (), {}) # classname, base classes, class attributes
and
class B(A):>>> class A:
... def __init__(self, *args):
... print("__init__{}".format(args))
...
>>> class B(A()): pass
...
__init__()
__init__('B', (<__main__.A object at 0x7f3db8a1c048>,), {'__module__':
'__main__', '__qualname__': 'B'})
>>> assert isinstance(B, A)
>>> isinstance(B, A)
>>>
>>>
True
>>> B()
>>>
>>>
Traceback (most recent call last):
File "", line 1, in
TypeError: 'A' object is not callable
foo = 42
is roughly equivalent to
B = type(A)("B", (A,), {"foo": 42})
When you subclass from an instance of A instead of A itself this becomes
a = A()
B = type(a)("B", (a,), {"foo": 42})
which can be simplified to
B = A("B", (a,), {"foo": 42})
If this succeeds B is bound to an instance of A, but usually you'll see a
TypeError, either immediately as the OP,
>>> class A: pass
...
>>> class B(A()): pass
...
Traceback (most recent call last):
File "", line 1, in
TypeError: object() takes no parameters
or later when you try to instantiate B:
>>> class A:
... def __init__(self, *args):
... print("__init__{}".format(args))
...
>>> class B(A()): pass
...
__init__()
__init__('B', (<__main__.A object at 0x7f3db8a1c048>,), {'__module__':
'__main__', '__qualname__': 'B'})
>>> isinstance(B, A)
>>>
>>>
True
>>> B()
>>>
>>>
Traceback (most recent call last):
File "", line 1, in
TypeError: 'A' object is not callable
> But I'm pretty sure you don;t want to subclass your
> imported module and thats the mistake.
__
Re: [Tutor] problem with a sub-class
On 30/11/17 15:37, Shall, Sydney wrote: > My problem is with constructing a sub-class. > > My sub-class is constructed as follows: > > import Population_ProductivityV24 as POCWP Note that POCWP is an alias for the *module* Population_ProductivityV24. It is not a class. > line 27 : class SimulateCycleZero(POCWP): Here you define a class that subclasses your imported module. Frankly I'm surprised that you don't get an error there but hey... > line 28 : def __init__(self, dirname_p): But this is now an init for a subclass of module. > The error message is as follows: > >File > "/Users/sydney/AnacondaProjects/Capital/Capital_with_productivity/Current_Versions/Simulate_Cycle_Zero_V3.py", > > line 27, in > class SimulateCycleZero(POCWP): > > TypeError: module.__init__() takes at most 2 arguments (3 given) So I'm guessing the use of a module to subclass has confused things and I confess I'm not clear on exactly what is going on and why you get this message. But I'm pretty sure you don;t want to subclass your imported module and thats the mistake. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] problem with a sub-class
I am almost a beginner. I have an error message which I cannot understand. My problem is with constructing a sub-class. I use; MAC OS V10.13.1 Anaconda Python 3.5 My base Class works properly and all 136 tests of the Base Class are correct. My sub-class is constructed as follows: import sys import random import numpy as np import pylab import copy import Population_InitV8 as POCI import Population_ProductivityV24 as POCWP line 27 : class SimulateCycleZero(POCWP): line 28 : def __init__(self, dirname_p): The program follows on from this. The error message is as follows: File "/Users/sydney/AnacondaProjects/Capital/Capital_with_productivity/Current_Versions/Simulate_Cycle_Zero_V3.py", line 27, in class SimulateCycleZero(POCWP): TypeError: module.__init__() takes at most 2 arguments (3 given) My problem is that I do not understand to which file the word 'module' in the error message applies. It seems to me that somewhere I am providing 3 arguments when only a maximum of two are required. When I do the following, I get the same error message. line 27 : class SimulateCycleZero(POCWP): line 28 : def __init__(self): I would appreciate some guidance , please. Sydney _ Professor Sydney Shall Department of Haematology/Oncology Phone: +(0)2078489200 E-Mail: sydney.shall [Correspondents outside the College should add @kcl.ac.uk] ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
