# Count of elements matching particular condition in Python

PythonServer Side ProgrammingProgramming

In this article we will see how to get some selected elements out of a Python list. So we need to design some condition and only the elements satisfying that condition should be picked and their count to be printed.

## Wit in and sum

In this approach we use in condition to pick the elements and use some to get their count. 1 is used if the element is present else 0 is used for the result of in condition.

## Example

Live Demo

Alist = ['Mon', 'Wed', 'Mon', 'Tue', 'Thu']
# Given list
print("Given list:\n", Alist)
cnt = sum(1 for i in Alist if i in('Mon','Wed'))
print("Number of times the condition is satisfied in the list:\n",cnt)

## Output

Running the above code gives us the following result −

Given list:
['Mon', 'Wed', 'Mon', 'Tue', 'Thu']
Number of times the condition is satisfied in the list:
3

## With map and lambda

Here also used in condition but also use lambda and map functions. Final we apply the sum function to get the count.

## Example

Live Demo

Alist = ['Mon', 'Wed', 'Mon', 'Tue', 'Thu']
# Given list
print("Given list:\n", Alist)
cnt=sum(map(lambda i: i in('Mon','Wed'), Alist))
print("Number of times the condition is satisfied in the list:\n",cnt)

## Output

Running the above code gives us the following result −

Given list:
['Mon', 'Wed', 'Mon', 'Tue', 'Thu']
Number of times the condition is satisfied in the list:
3

## With reduce

The reduce function applies a particular function to all the elements in a list supplied to it as an argument. We use it along with a in condition finally producing the count of the elements matching the condition.

## Example

Live Demo

from functools import reduce
Alist = ['Mon', 'Wed', 'Mon', 'Tue', 'Thu']
# Given list
print("Given list:\n", Alist)
cnt = reduce(lambda count, i: count + (i in('Mon','Wed')), Alist, 0)
print("Number of times the condition is satisfied in the list:\n",cnt)

## Output

Running the above code gives us the following result −

Given list:
['Mon', 'Wed', 'Mon', 'Tue', 'Thu']
Number of times the condition is satisfied in the list:
3
Published on 04-Jun-2020 11:31:05