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Membership testing in Python

schedule Aug 12, 2023
Last updated
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Python
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Membership testing in Python checks to see if a value is part of a sequence such as a list or set. We can perform membership testing using the in operator or not in operator.

To check whether 'a' is in the list my_list:

my_list = ['a', 'b', 'c']
'a' in my_list
True

For a performance boost, note that membership testing with a set is significantly faster than using a list or a tuple:

my_list = ['a', 'b', 'c', 'd','e','f','g']
my_set = {'a', 'b', 'c', 'd', 'e', 'f', 'g'}

%timeit 'g' in my_list
%timeit 'g' in my_set
159 ns ± 53.2 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
44.9 ns ± 2.62 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
robocat
Published by Arthur Yanagisawa
Edited by 0 others
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