Python Count Occurrence Of Elements

There are several ways to count the occurrence of elements in a Python list. One way is to use the list.count() method which takes an element as an argument and returns the number of times it appears in the list. For example:

a = [1, 2, 3, 4, 1, 2, 1]
b = a.count(1) # b is 3
c = a.count(5) # c is 0

Another way is to use a loop and a counter variable to iterate over the list and increment the counter whenever the element is found. For example:

a = [1, 2, 3, 4, 1, 2, 1]
x = 1
count = 0
for ele in a:
    if ele == x:
        count += 1
# count is 3 

A third way is to use a dictionary or a defaultdict to store the elements as keys and their counts as values. For example:

from collections import defaultdict

a = [1, 2, 3, 4, 1 ,2 ,1]
occurrence = defaultdict(lambda:0)
for ele in a:
    occurrence[ele] += 1
# occurrence is {1:3 ,2:2 ,3:1 ,4:1}

It is good to have an idea of the number of times elements occurred in your data structure.

from collections import Counter
data= [96,95,96,87,87,88,56,57,57]occurences = Counter(data)
print(occurences)
# output Counter({96: 2, 87: 2, 57: 2, 95: 1, 88: 1, 56: 1})

If you have any questions about this code, you can drop a line in comment.

 

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