How do you count the number of occurrences in a list?

Below are the three solutions:

Fastest is using a for loop and storing it in a Dict.

Table of Contents Show

Below are the three solutions:
Python | Count occurrences of an element in a list
Python List count()
How to count the number of occurrences of a list item in Python
Use .count() to Count Number of Occurrences in a Python List

import time from collections import Counter def countElement(a): g = {} for i in a: if i in g: g[i] +=1 else: g[i] =1 return g z = [1,1,1,1,2,2,2,2,3,3,4,5,5,234,23,3,12,3,123,12,31,23,13,2,4,23,42,42,34,234,23,42,34,23,423,42,34,23,423,4,234,23,42,34,23,4,23,423,4,23,4] #Solution 1 - Faster st = time.monotonic() for i in range(1000000): b = countElement(z) et = time.monotonic() print(b) print('Simple for loop and storing it in dict - Duration: {}'.format(et - st)) #Solution 2 - Fast st = time.monotonic() for i in range(1000000): a = Counter(z) et = time.monotonic() print (a) print('Using collections.Counter - Duration: {}'.format(et - st)) #Solution 3 - Slow st = time.monotonic() for i in range(1000000): g = dict([(i, z.count(i)) for i in set(z)]) et = time.monotonic() print(g) print('Using list comprehension - Duration: {}'.format(et - st))

Result

#Solution 1 - Faster

{1: 4, 2: 5, 3: 4, 4: 6, 5: 2, 234: 3, 23: 10, 12: 2, 123: 1, 31: 1, 13: 1, 42: 5, 34: 4, 423: 3} Simple for loop and storing it in dict - Duration: 12.032000000000153

#Solution 2 - Fast

Counter({23: 10, 4: 6, 2: 5, 42: 5, 1: 4, 3: 4, 34: 4, 234: 3, 423: 3, 5: 2, 12: 2, 123: 1, 31: 1, 13: 1}) Using collections.Counter - Duration: 15.889999999999418

#Solution 3 - Slow

{1: 4, 2: 5, 3: 4, 4: 6, 5: 2, 34: 4, 423: 3, 234: 3, 42: 5, 12: 2, 13: 1, 23: 10, 123: 1, 31: 1} Using list comprehension - Duration: 33.0

Python | Count occurrences of an element in a list

Given a list in Python and a number x, count number of occurrences of x in the given list.
Examples:

Input : lst = [15, 6, 7, 10, 12, 20, 10, 28, 10] x = 10 Output : 3 10 appears three times in given list. Input : lst = [8, 6, 8, 10, 8, 20, 10, 8, 8] x = 16 Output : 0

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Method 1 (Simple approach)
We keep a counter that keeps on increasing if the required element is found in the list.

Python3

# Python code to count the number of occurrences

def countX(lst, x):

count = 0

for ele in lst:

if (ele == x):

count = count + 1

return count
# Driver Code

lst = [8, 6, 8, 10, 8, 20, 10, 8, 8]

x = 8

print('{} has occurred {} times'.format(x, countX(lst, x)))

Output: 8 has occurred 5 times

Method 2 (Using count())
The idea is to use list method count() to count number of occurrences.

Python3

# Python code to count the number of occurrences

def countX(lst, x):

return lst.count(x)
# Driver Code

lst = [8, 6, 8, 10, 8, 20, 10, 8, 8]

x = 8

print('{} has occurred {} times'.format(x, countX(lst, x)))

Output: 8 has occurred 5 times

Method 2 (Using Counter())
Counter method returns a dictionary with occurrences of all elements as a key-value pair, where key is the element and value is the number of times that element has occurred.

Python3

from collections import Counter
# declaring the list

l = [1, 1, 2, 2, 3, 3, 4, 4, 5, 5]
# driver program

x = 3

d = Counter(l)

print('{} has occurred {} times'.format(x, d[x]))

Output: 3 has occurred 2 times

Article Tags :

Python

Python list-programs

python-list

Practice Tags :

python-list

Read Full Article

Python List count()

In this tutorial, we will learn about the Python List count() method with the help of examples.

The count() method returns the number of times the specified element appears in the list.

Example

# create a list numbers = [2, 3, 5, 2, 11, 2, 7]

# check the count of 2 count = numbers.count(2)

print('Count of 2:', count) # Output: Count of 2: 3

How to count the number of occurrences of a list item in Python

Use .count() to Count Number of Occurrences in a Python List

The easiest way to count the number of occurrences in a Python list of a given item is to use the Python .count() method. The method is applied to a given list and takes a single argument. The argument passed into the method is counted and the number of occurrences of that item in the list is returned.

Let’s see how we can use the .count() method to count the number of occurrences in a Python list:

# Count the Number of Occurrences in a Python list using .count() items = ['a', 'b', 'a', 'c', 'd', 'd', 'd', 'c', 'a', 'b'] count_a = items.count('a') print(f'{count_a=}') # Returns: count_a=3

We can see here that when we apply the .count() method to a list and pass in the item that we want to count, that the number of occurrences are returned.

Let’s see what would happen if we pass in an item that does not exist in the list:

# Count the Number of Occurrences in a Python list using .count() items = ['a', 'b', 'a', 'c', 'd', 'd', 'd', 'c', 'a', 'b'] count_f = items.count('f') print(f'{count_f=}') # Returns: count_f=0

When an item doesn’t exist in a list and the .count() method is applied, the value of 0 is returned.

This method is a very Pythonic way to get the number of occurrences in a Python list for a single item. However, if you wanted to count the number occurrences of more than one item in a list, it’d be much better to use a different method, such as the Counter library.

This is exactly what you’ll learn in the next section!

Need to automate renaming files? Check out this in-depth guide on using pathlib to rename files. More of a visual learner, the entire tutorial is also available as a video in the post!