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[Python] Attributes vs dictionary

post #1 of 5
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Really quick question - I'm wondering whether it's better to have a class definition with 8 seperate attributes (and methods, of course!), or whether to have a single dictionary with the values in there? My gut feel says attributes will be more readable, but I'm not sure whether it's the right way to go from a performance/memory usage perspective (and which way is the 'proper' way to go). This is Python 2 btw, but answers satisfying both would be nice
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post #2 of 5
I don't know much about Python, but having direct access to a variable is always faster than a dictionary due to lookup times. I'm speaking from a C++/C# perspective, a dictionary might be different in Python.
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post #3 of 5
Thread Starter 
Quote:
Originally Posted by lordikon View Post
I don't know much about Python, but having direct access to a variable is always faster than a dictionary due to lookup times. I'm speaking from a C++/C# perspective, a dictionary might be different in Python.
It's implemented in C, so I'd expect the same (or similar) rules apply. I've since found out that all variables/attributes of a Python object are dictionaries anyway, so I suspect it's a moot point. I'll go with the attributes I think, as a container object is just an extra layer of abstraction that I don't need to worry about.

I've also thought about it since the OP, and I've realised that I'm going to need getter/setter methods (although I might use properties somehow) on this class, which takes away a bit of the worry. I'm trying to re-use as much code as possible, as the program will be doing the same things many times to many lots of data. The less code, the less likely an annoying typo might cause an annoying bug
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post #4 of 5
Use attributes if you know what each one is called, i.e. their names remain static.

Use the dictionary if you're doing something more clever and dynamic, i.e. their names are calculated and/or you have a variable number of keys.

We have classes with dozens of fields... yes it sucks but it's the right way to do it. As far as the computer is concerned there's no difference between a class with one field or one thousand - use what ever gives the best representation of your object as it exists in real life; model it outside the code first and then it will easily translate.

Some of their data models at work are so harebrained, absolutely not even close to the way things really are when looked at through the glasses of real-world simplicity, it drives me crazy. Ever try to build an entire _stable app on top of a nonsense data model??? Instead of data clearly dictating relationships and behavior, we have data that doesn't make any sense, and then a whole set of nonsense rules on top of the nonsense data to try and make a lick of sense out of it. it's totally crazy
Edited by lloyd mcclendon - 8/17/11 at 9:25pm
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post #5 of 5
Thread Starter 
Yeah, I've gone with the attributes - one hell of an ugly __init__ method though
I'm focussing on the data first (pretty much the only thing I've worked on so far), then I'll start slowly building up methods & other classes to provide the actual functionality. It feels like the right way to go; I'll only run into difficulty when the method start interacting and calling each other. It's hard to make the code remain "dynamic" where things are passed into the method rather than being hard-coded there. I'm not that experienced...

I'm also making the switch to Python 3 - mostly it seems the same, but I'm bound to mess it up somewhere
Oh, and I'm going to code the program seperately from the GUI - never done that one before, but this project is too huge to get all the GUI crap in the way. In that respect, I like the way Android does it - code in Java/Dalvik, GUI in XML. Completely seperate, it's really neat
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