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Date: Tue, 21 Jan 2014 21:03:56 +0000
Subject: Re: how to avoid spaghetti in Python?
From: andrea crotti <andrea.crotti.0@gmail.com>
To: CM <cmpython@gmail.com>
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2014/1/21 CM <cmpython@gmail.com>:
> I've been learning and using Python for a number of years now but never r=
eally go particularly disciplined about all good coding practices.  I've de=
finitely learned *some*, but I'm hoping this year to take a good step up in=
 terms of refactoring, maintainability, and mostly just "de-spaghettizing" =
my approach to writing Python programs.
>

It's not really a problem of Python, you just want to learn more about
OO principles and good design practices, and about that there are
hundreds of good books to read!

>
> A few specific questions in this area...
>
> 1) One of my main "spaghetti problems" is something I don't know what to =
ever call.  Basically it is that I sometimes have a "chain" of functions or=
 objects that get called in some order and these functions may live in diff=
erent modules and the flow of information may jump around quite a bit, some=
times through 4-5 different parts of the code, and along the way variables =
get modified (and those variables might be child objects of the whole class=
, or they may just be objects that exist only within functions' namespaces,=
 or both).  This is hard to debug and maintain.  What would people recommen=
d to manage this?  A system of notes?  A way to simplify the flow?  And wha=
t is this problem called (if something other than just spaghetti code) so I=
 can Google more about it?
>

Just define clearly objects and methods and how they interact with
each other in a logic way, and you won't have this problem anymore.

> 2) A related question:  Often I find there are two ways to update the val=
ue of an object, and I don't know what's best in which circumstances... To =
begin to explain, let's say the code is within a class that represents a Fr=
ame object in a GUI, like wxPython.  Now let's say ALL the code is within t=
his wxFrame class object.  So, any object that is named with "self." prepen=
ded, like self.panel, or self.current_customer, or self.current_date, will =
be a child object of that frame class, and therefore is sort of "global" to=
 the whole frame's namespace and can therefore be accessed from within any =
function in the class. So let's say I have a function called self.GetCurren=
tCustomer().  To actually get the name of the current customer into RAM, it=
 goes into the database and uses some rule to get the current customer.  NO=
W, the question is, which of these should I do?  This:
>
>       def GetCurrentCustomer(self):
>           self.current_customer =3D #do some database stuff here....
>
> Or this:
>
>       def GetCurrentCustomer(self):
>           current_customer =3D #do some database stuff here....
>           return current_customer
>
> And what difference does it make?  In the first case, I am just updating =
the "global" object of the current_customer, so that any function can then =
use it.  In the second case, I am only returning the current_customer to wh=
atever function(s) call this GetCurrentCustomer() function.
>

GetCurrentCustomer should be really get_current_customer if you don't
want people screaming at you.
And about the question it depends, is the database stuff going to be expens=
ive?
Do you need to have always a new value?

And by the way  if you're never actually using "self" in a method
maybe it should be a function, or at least a classmethod instead.

> My hunch is the first way leads to spaghetti problems.  But I want to und=
erstand what the best practices are in this regard. I have found in some ca=
ses the first method seemed handy, but I'm not sure what the best way of th=
inking about this is.
>
> 3) Generally, what are other tools or approaches you would use to organiz=
e well a good-sized project so to avoid fighting yourself later when you do=
n't understand your own code and the flow of information through it?  By go=
od sized, say about 20,000 lines of Python code, or something like that.
>

Good architecture and some meaningful directory structure is good
enough, to navigate Emacs + ack and I'm already very productive even
with bigger projects than that.