what is happening at __init__

[Benjamin Tai]

Hi,

I was simply curious, finding out what is happening at the class
constructor. The followings are the questions/answers that I come up
with, in related with my program attached:

Q 1) "self" is already assigned to the instance of the class at the
point entering the constructor.
Q 2) Although "self" is assigned to a new value within the function, it
is in a local scope.
Q 3) A constructor must return None, it cannot return "self".
Q 4) The address of instance matches with the instance within the
constructor.
Q 5) Even though the constructor returns None, the instance is properly
initialised (with inherited attributes).



The following is my program:

#############

class A:
    x = 100

class B(A):

    def __init__(self):
        #  Q1
        print 'inside constructor self is ', self
        self = 300
        # Q2
        print 'inside constructor self is ', self
        # Q3
        return None

b = 200
b = B()
print 'after constructor instance b is ', b
# Q4
print 'instance b contains attribute x, valued ', b.x
# Q5

############


The following is the trace:

prompt > inside constructor self is  <__main__.B instance at 0x80e9c94>
prompt > inside constructor self is  300
prompt > after constructor instance b is  <__main__.B instance at
0x80e9c94>
prompt > instance b contains attribute x, valued  100




Could anyone tell me whether the explanation is correct or not? Any
comments would be appreciated.

Thanks

Ben