Why self?

[David LeBlanc]

What do you know - another programmer whose first encounter with a computer
didn't involve killing 4,000 aliens from the planet "Mongo"!

Well said!

Now if someone would just stand up and call eXtreme Programming the EXtreme
BS that it is! :P

BTW, Charles Semeyonie (sp?) who originated "hungarian" notation has
repented publically. It started out as a learning aid for newbie MS
programmers and grew an evil life of it's own.


David LeBlanc
Seattle, WA USA

> -----Original Message-----
> From: python-list-admin at python.org
> [mailto:python-list-admin at python.org]On Behalf Of Matt Gerrans
> Sent: Friday, July 05, 2002 19:24
> To: python-list at python.org
> Subject: Re: Why self?
>
>
> > What I mean by the legacy part is that you have to name self in the
> > list of arguments to the class methods.
> > This part is redundant - but once you are inside a method, it is fine
> > that you have to explicitly qualify by self when refering to class
> > variables.
>
> I kind of like this part of the syntax, especially when using
> os.path.walk()
> with a walker method in a class; it is very clear what is going
> on with the
> "self" pointer, as opposed to the implicit pointer in C++ which can be
> confusing in similar circumstances.
>
> > As holger points out, a frequent source of errors in C++ is that a
> > method takes an argument with the same name as a class variable -
> > which then hides the class variable.
>
> I don't agree with this argument -- a simple compiler warning solves this
> problem; no need to throw out the baby with the bath water.   I also don't
> think it is a frequent source of errors.
>
> In Python, I think the required "self" reference in methods is a
> case where
> the solution is worse than the problem it solves.   Since
> indentation is the
> method of scoping in Python, this addition of five characters to each
> instance variable is particularly annoying -- a one-line statement that
> contains several instance variables can easily become unmanageable.
>
> It's a bit like that horrible blight on the programming community called
> "Hungarian Notation" that needlessly polutes code with incomprehensible
> variable prefixes so that you know your string is really a long
> pointer to a
> zero terminated array of signed 8-bit characters.   As if you cared, or
> needed to be constantly innundated with such superfluous information.
> Fortunately, the Hungarian Notation investation has for the most part been
> limited to Microsoft's C and C++ APIs and thier usage, but hasn't infected
> others -- and nowadays it even seems to be on the decline in Redmond (C#
> examples are generally free of it).
>
> I never had a much of problem in C++ with distinguishing member variables
> from local variables and I never liked those cheesy ("Some cheese, please,
> my good man!") conventions of always using "m_" or "this->".   If you keep
> your methods small and clean, you don't need all this slop.
>
> However, since Python doesn't have declarations, some method is
> required to
> distinguish whether an assignment in a class's method is an
> assignment to a
> instance variable or a local variable.   I prefer the solution of simply
> making it illegal to have local variable names match class variable names.
> Hmm... this doesn't help with the problem of globals, but there
> is a keyword
> for that.
>
> > When I prototype new classes, the methods often start out as
> > functions, and typically I forget to add self to the argument list
> > when they are promoted to methods.
>
> Me too!
>
>
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