The problem with using tuples and lists to hold structures

August 18, 2008

If you need to hold several bits of data about something in Python, it's awfully tempting to just put everything into a tuple or a list and be done with it; it's certainly the easiest way, and so crops up often.

(I've read that that Pythonic way to decide between a list and a tuple is whether or not the data is all the same type, in which case you use a tuple, or different types, in which case you use a list. I don't bother paying attention to this; I generally use a tuple if the data elements don't get changed and a list if they do.)

The problem with using lists and tuples instead of actual structures for this is that you are stuffing structured data into unstructured objects. The result is that the structure of the data only exists implicitly in your code, instead of explicitly in the objects. This is both harder to read and more prone to errors (especially since the structure of the data is going to be in more than one place, all of which had better agree).

All of this makes me think that I should be using some sort of structures in my Python code much more than I am now. Even if the idiom itself takes some explaining, I think that the overall code will be simpler and clearer.

(And the basic version is not all that much code, either.)

Update: I was wrong about the Python use of lists and tuples; it is lists that are for data that is all the same type, and tuples for data that is a different type. See the comments for details.

Written on 18 August 2008.
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Last modified: Mon Aug 18 22:32:23 2008
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