[Tutor] super constructor usage

[Mats Wichmann]

On 03/29/2017 04:02 PM, Mats Wichmann wrote:
> On 03/29/2017 08:33 AM, Rafael Knuth wrote:
> 
>> class A:
>>     def __init__(self, message):
>>         self.message = message
>>         print(message)
>>
>> I then modified the child class B like this:
>>
>> class B(A):
>>     def __init__(self, message):
>>         print("This is the message from your parent class A:")
>>         super(B, self).__init__(message)
>>
>> B("BlaBla")
>>
>> That works, however I am not sure about what exactly happens inside the code.
>> What I am concerned about is whether the argument is being actually
>> inherited from the parent class A or does B overwrite the argument.
>> Can anyone advise what the correct solution would be (in case mine is wrong).
>> Thank you.
> 
> Alan (as usual) already sorted this.
> 
> Just to try to fill in some of these questions - what's inherited,
> overridden, etc., I'm pasting a bit of code I wrote for somewhere else
> to demonstrate what's going on. 

etc.

To make sure there's an even simpler answer than poring through all
those cases (which I think is useful), also try this minimal rewrite of
your example:

class A(object):
    def __init__(self, message):
        self.message = message + " (decorated by superclass)"

class B(A):
    def __init__(self, message):
        print("Class B initializer called with %s argument" % message)
        super().__init__(message)

b = B("BlaBla")
print("instance message =", b.message)