[Tutor] Hello and newbie question about "self"

Patrick python-list at puzzled.xs4all.nl
Mon Feb 4 01:38:52 CET 2008

Hi Alan,

Alan Gauld wrote:
> "Patrick" <python-list at puzzled.xs4all.nl> wrote 
>> Can anyone please point me to a document that explains "self" in
>> layman's terms. 
> Try the OOP topic inmy tutorial...

Thanks will have a look.

>> Or lacking such a doc throw in a much appreciated
>> layman's explanation what "self" is and when/where to use it? 
> Others have given code samples but a conceptuial explanation 
> is that 
> a) self is only used in OO programming within metjhods of a class.

Now that really helps. I was wondering about that and this answers it.

> b) self refers to the actual instance of the object receiving the 
>     message with caused the method to be invoked.

This and reading chapter 23 in the book makes things much clearer now.

> Thus if we have a class C with a method m and 3 instances 
> a,b and z then when we invoke a.m() self will refer to a and 
> when we invoke b.m() self will refer to b. This means that the 
> innards of the method can use self to access the instance 
> specific data for that invocation.

Even more clear now :)

> If you have used C++ at all you might recognise it as the 
> same as 'this' in C++ except that in Python you must explicitly 
> specify it whereas C++ creates 'this' magically behind the scenes.

Last time I used C++ was (iirc) in 1987 with a Borland product. I recall
"this" and remember I got stuck on it then too.

> See my tutorial for more on this under the heading 
> "Using classes".

Will do. Thanks for the pointer.

> If you haven't started writing classes yet, you can safely ignore 
> it for now!

I probably won't need to start writing classes but I really want to
finish the book before I start coding something. I have a small script I
did in (horrible) bash and look forward to try to implement it in (less
horrible) Python.

Thanks for your help.


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