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 Explanation: 10 appears three times in given list. Input: lst = [8, 6, 8, 10, 8, 20, 10, 8, 8], x = 16 Output: 0 Explanation: 16 appears zero times in given list.
Method 1: Count occurrences of an element in a list Using a Loop in Python
We keep a counter that keeps on increasing if the required element is found in the list.
Python3
def countX[lst, x]:
count = 0
for ele in
lst:
if [ele == x]:
count = count + 1
return count
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 an element in a list Using count[]
The idea is to use the list method count[] to count the number of occurrences.
Python3
def countX[lst, x]:
return lst.count[x]
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 an element in a 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
l =
[1, 1, 2, 2, 3, 3, 4, 4, 5, 5]
x = 3
d = Counter[l]
print['{} has occurred {} times'.format[x, d[x]]]
Output:
3 has occurred 2 times
Method 4: Count occurrences of an element in a list Using countof[]
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
l =
[1, 1, 2, 2, 2, 3, 3, 4, 4, 5, 5]
x = 2
print[f"{x} has occurred {op.countOf[l, x]} times"]
Output:
2 has occurred 3 times
Method 5: Count occurrences of an element in a list Using 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: Count occurrences of an element in a list 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
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
Method: Using list comprehension
Python3
l =
[1, 1, 2, 2, 2, 3, 3, 4, 4, 5, 5]
ele=1
x=[i for i in l if i==ele]
print["the element",ele,"occures",len[x],"times"]
Output
the element 1 occures 2 times