A common task when working with lists is to count the occurrence of an element.

There are a few ways through which we can achieve this, in this article we will go through these methods and understand them with examples.

Using For loop

A simple for loop can be used with a counter variable which can be incremented every time the target element is found.

Example:

target = 3
source_list = [1, 0, 3, 4, 3, 8, 3]

count = 0
for element in source_list:
    if element == target:
        count += 1
print("Element {target} occured {count} times in {source_list}")

Output:

Element 3 occurred 3 times in [1, 0, 3, 4, 3, 8, 3]

Using count() method

The list data structure in Python has a count() method which returns the count of an element given as a parameter.

Example:

source_list = [1, 0, 3, 4, 3, 8, 3]

print(source_list.count(3))

Output:

3

It is important to note that the count() method makes a complete pass over the list every time it is ran, therefore for counting multiple elements use the collections.Counter approach.

Using collections.Counter

The Python standard library collections can be used to get a count of each and every element in a list. The value returned by the Counter method is a dictionary with the element and its count as key-value pairs.

Example:

from collections import Counter

source_list = [1, 0, 3, 4, 3, 8, 3]

counts_dictionary = Counter(source_list)
print(counts_dictionary)

Output:

Counter({3: 3, 1: 1, 0: 1, 4: 1, 8: 1})

Using operator.countOf()

operator is amongst the standard libraries that come preinstalled with Python. Its countOf() method can be used to count the occurrence of an element in a list.

Example:

from operator import countOf

source_list = [1, 0, 3, 4, 3, 8, 3]

print(countOf(source_list, 3))

Output:

3