Python | Count occurrences of an element in a list

Given a list in Python and a number x, count the 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

Method 1: Count Occurrences of Element in Python List using a loop in python

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: Count Occurrences of Element in Python List using count()

The idea is to use the list method count() to count the 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 3: Count Occurrences of Element in Python List using Counter()

The counter method returns a dictionary with occurrences of all elements as a key-value pair, where the key is the element and the 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

Method 4: Count Occurrences of Element in Python List using countof() method

Operator.countOf() is used for counting the number of occurrences of b in a. It counts the number of occurrences of value. It returns the Count of a number of occurrences of value.

Python3

import operator as op

# declaring the list
l = [1, 1, 2, 2, 2, 3, 3, 4, 4, 5, 5]

# driver program
x = 2
print(f"{x} has occurred {op.countOf(l, x)} times")

Output:

2 has occurred 3 times

Method 5: Count the Number of Occurrences using a dictionary comprehension

Python allows dictionary comprehensions. We can create dictionaries using simple expressions. A dictionary comprehension takes the form {key: value for (key, value) in iterable}

Python3

lis = ['a', 'd', 'd', 'c', 'a', 'b', 'b', 'a', 'c', 'd', 'e']
occurrence = {item: lis.count(item) for item in lis}
print(occurrence.get('e'))

Output:

1

Method 6: Using the panda’s library

Pandas Series.value_counts() function return a Series containing counts of unique values. The resulting object will be in descending order so that the first element is the most frequently-occurring element.

Python3

import pandas as pd

# declaring the list
l = [1, 1, 2, 2, 2, 3, 3, 4, 4, 5, 5]

count = pd.Series(l).value_counts()
print ("Element    Count")
print(count)

Output:

Element    Count
2    3
1    2
3    2
4    2
5    2
dtype: int64