Check if element exists in tuple of tuples

Question

I have a list of tuples that look like :

CODES = (     ('apple', 'reddelicious'),     ('caramel', 'sweetsticky'),     ('banana', 'yellowfruit'), ) 

What's the best way to check if a value exists in that tuple? For example I want to be able to say:

'apple' in CODES 

and get True

Answer 1

You are looking for any():

if any('apple' in code for code in CODES):     ... 

Combined with a simple generator expression, this does the task. The generator expression takes each tuple and yields True if it is contains 'apple'. any() then returns True when the first item it requests returns True (otherwise, False). Hence this does what you want. It also reads nicely - if any of the tuples contain 'apple'.

If you are doing this a massive number of times and need performance, then it might be worth making a set of all of the values to allow you to do this very quickly:

cache = set(itertools.chain.from_iterable(CODES))) 

Naturally, constructing this will be slow and use memory, so it wouldn't be a good idea unless you need a lot of performance and will be doing a lot of membership checks.

Answer 2

You can use itertools.chain():

Using it with in will result in short-circuiting, similar to any().

In [30]: CODES = (    ....:     ('apple', 'reddelicious'),    ....:     ('caramel', 'sweetsticky'),    ....:     ('banana', 'yellowfruit'),    ....: )   In [31]: from itertools import chain  In [32]: 'apple' in chain(*CODES) Out[32]: True  In [33]: 'foo' in chain(*CODES) Out[33]: False 

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For performance comparisons you can check my other answer.