2014/1/21 CM <cmpyt...@gmail.com>: > I've been learning and using Python for a number of years now but never > really go particularly disciplined about all good coding practices. I've > definitely 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 > different modules and the flow of information may jump around quite a bit, > sometimes 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 > recommend to manage this? A system of notes? A way to simplify the flow? > And what 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 value > 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 Frame > object in a GUI, like wxPython. Now let's say ALL the code is within this > wxFrame class object. So, any object that is named with "self." prepended, > 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.GetCurrentCustomer(). 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. NOW, the question is, which of these should I do? This: > > def GetCurrentCustomer(self): > self.current_customer = #do some database stuff here.... > > Or this: > > def GetCurrentCustomer(self): > current_customer = #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 whatever > 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 expensive? 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 > understand what the best practices are in this regard. I have found in some > cases the first method seemed handy, but I'm not sure what the best way of > thinking about this is. > > 3) Generally, what are other tools or approaches you would use to organize > well a good-sized project so to avoid fighting yourself later when you don't > understand your own code and the flow of information through it? By good > 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. -- https://mail.python.org/mailman/listinfo/python-list
