Given a single item, how do I count occurrences of it in a list, in Python?
A related but different problem is counting occurrences of each different element in a collection, getting a dictionary or list as a histogram result instead of a single integer. For that problem, see Using a dictionary to count the items in a list.
Best Answer
If you only want a single item's count, use the
count
method:Important: this is very slow if you are counting multiple different items
Each
count
call goes over the entire list ofn
elements. Callingcount
in a loopn
times meansn * n
total checks, which can be catastrophic for performance.If you want to count multiple items, use
Counter
, which only doesn
total checks.