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# Membership testing in Python

schedule Aug 12, 2023
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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) ```
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