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Python find item in list

Last Updated on Wednesday 5th Oct 2022

python where in list

Checking if something is inside

Checking whether something is inside a list or not.You can use the in operator.

					3 in [1, 2, 3] # => True


python find in list

Filtering a collection

Finding all elements in a sequence that meet a certain condition. You can use list comprehension or generator expressions for that

					matches = [x for x in lst if fulfills_some_condition(x)]
matches = (x for x in lst if x > 6)


Finding the location of an item

					[1,2,3].index(2) # => 1
[1,2,3].index(4) # => ValueError


python list find

if you have duplicates, .index always returns the lowest index

					[1,2,3,2].index(2) # => 1


python search list

Finding the first occurrence

If you only want the first thing that matches a condition (but you don't know what it is yet), it's fine to use a for loop

					next(x for x in lst if ...)
next((x for x in lst if ...), [default value])


If there are duplicates and you want all the indexes then you can use enumerate()

					[i for i,x in enumerate([1,2,3,2]) if x==2] # => [1, 3]


python find item in list