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Using a variable from one class to another one in python

I want to use a variable from class A for some computation in class B. I,m not sure that I use the self.out from the class A in class B appropriately?
Class A:
class A(nn.Module):
def __init__(self):
super(A, self).__init__()
self.out = func()
Class B:
class B(nn.Module):
def __init__(self):
super(A, self).__init__()
self.result = function_1() + A.self.out

Maybe this is what you need. I made a small example of what I understood.
These "prints" were placed to improve the understanding that Class "C" can fetch any function or variable from the other parent classes.
class A():
def __init__(self):
variable = None
def test(self, number):
return f'another class {number}'
class B():
def __init__(self):
self.data = None
self.out = self.print_data(5)
def print_data(self, number):
return number
def print_elem(self):
return self.data
class C(A, B):
def __init__(self):
super().__init__()
c = C()
print(c.print_data(8))
print(c.out)
c.data = 100
print(c.print_elem())
print(c.test(3))

Python encapsulate data for a class

I have two python classes, A and B that inherits from A.
At runtime, I only have one instance of class A, but many instances of class B.
class A:
def __init__(self, a):
self.a = a
def _init2 (self, AA)
self.a = AA.a
class B(A):
def __init__(self, AA, b):
super()._init2(AA)
self.b = b
AA = A(0)
BB = B(AA, 1)
Is this the good way of writing it ? It seems ugly ...

It would probably be better to remove init2 and only use __init__. Having both is confusing and unnatural.
class A:
def __init__(self, obj):
# I believe that this is what you tried to achieve
if isinstance(obj, type(self)):
self.a = obj.a
else:
self.a = obj
class B(A):
def __init__(self, A, b):
super().__init__(A)
self.b = b
On a side note, there are too many things called A here. The A in def __init__(self, A, b): is most probably not referring to the A that you expect.

One constant value for multiple classes

Let's say that I have six different classes and three of them should use the same constant value. What can we do? We either:
Define as global variable
A = 1
class B:
def __init__(self):
self.a = A
class C:
def __init__(self):
self.a = A
class D:
def __init__(self):
self.a = A
Define as class level for 1 class and give it to another class:
class B:
A = 1
def __init__(self):
self.b = 2
class C:
def __init__(self, a):
self.a = a
self.b = 3
b = B()
c = B(a=b.A)
The second way I just made up and as for me it's dirty and not convenient. Is there any way to avoid using a global variable?

Use class inheritance:
class Holder:
a = 4
class A(Holder):
pass
print A().a

You could use inheritance, using B as the base class
class B:
A = 1
def __init__(self):
self.b = 2
class C(B):
def __init__(self):
B.__init__(self)
self.a = B.A
self.b = 3
b = B()
c = C()
print c.a

Accidentally calling an ovverriden method from base class's __init__

This program seems to do everything by the book, yet this issue cropped up: while a base class was being init'ed a member method was called that is overriden in the derived class and assumes that the derived class has been constructed.
Is there some best practice to protect against this?
#!/usr/bin/env python3
class A:
def __init__(self):
self.ax = 1
print(self)
def __repr__(self):
return "{} ax: {}".format(self.__class__.__name__, self.ax)
class B(A):
def __init__(self):
super().__init__()
self.bx = 10
def __repr__(self):
return super().__repr__() + " bx: {}".format(self.bx)
if __name__ == "__main__":
B()
And here's the error:
AttributeError: 'B' object has no attribute 'bx'

Generally, unless you really know what you are doing, you want to call the superclass initialization after everything your class needs to do is done. Same with this example, repr is trying to print self.bx before you initialize it. If you do
class B(A):
def __init__(self):
self.bx = 10
super().__init__()
def __repr__(self):
return super().__repr__() + " bx: {}".format(self.bx)
it works as expected

Edited:
Instead of doing computation on __init__, one idea may be to do that in a factory function/classmethod.
Example instead of doing:
class A:
def __init__(self, a, b):
self.a = a
self.b = b
self.initialize()
def initialize(self):
# do some things
Do:
class A:
def __init__(self, a, b):
self.a = a
self.b = b
#classmethod
def from_a_b(cls, a, b):
instance = cls(a, b)
instance.initialize()
return instance

using a variable from a method of another class in python

I have code that goes like this:
class A(object):
def __init__(self, master):
"""Some work here"""
def do_this(self):
self.B = B.do_that()
print self.B[1]
class B(object):
def __init__(self, master):
"""Some work here"""
def do_that(self):
p = (1, 2)
I can't make the method in class A to use that self.B as a tuple. Help.

For starters, do_that() doesn't return anything. So calling it will pretty much do nothing.
self.B = B.do_that() also won't work. You have to first create an instance of the class B:
mything = B(your_parameters)
mything.do_that()
And if you want that to return something (i.e, the tuple), you should change your do_that() to:
def do_that(self):
return (1, 2)
One final note, this can all be achieved through Inheritance:
class A(B): # Inherits Class B
def __init__(self,master):
"""Some work here"""
def do_this(self):
print self.do_that()[1] # This is assuming the do_that() function returns that tuple
Using the inheritance method:
>>> class B:
... def __init__(self, master):
... """Some work here"""
... def do_that(self):
... return (1,2)
...
>>> class A(B):
... def __init__(self, master):
... """Some work here"""
... def do_this(self):
... print self.do_that()[1]
...
>>> mything = A('placeholder')
>>> mything.do_this()
2

First you have to instantiate B as a property of A in the method A.do_this().
The following code should work.
def do_this(self):
b = B()
self.B = b.do_that()
print self.B[1]