Lambda and filter in Python Examples

Prerequisite : Lambda in Python

Given a list of numbers, find all numbers divisible by 13.

Input : my_list = [12, 65, 54, 39, 102, 
                     339, 221, 50, 70]
Output : [65, 39, 221]

We can use Lambda function inside the filter() built-in function to find all the numbers divisible by 13 in the list. In Python, anonymous function means that a function is without a name.

The filter() function in Python takes in a function and a list as arguments. This offers an elegant way to filter out all the elements of a sequence “sequence”, for which the function returns True.

# Python Program to find numbers divisible
# by thirteen from a list using anonymous
# function

# Take a list of numbers.
my_list = [12, 65, 54, 39, 102, 339, 221, 50, 70, ]

# use anonymous function to filter and comparing
# if divisible or not
result = list(filter(lambda x: (x % 13 == 0), my_list))

# printing the result
print(result)

Output:

[65, 39, 221]

Given a list of strings, find all palindromes.

# Python Program to find palindromes in
# a list of strings.

my_list = ["geeks", "geeg", "keek", "practice", "aa"]

# use anonymous function to filter palindromes.
# Please refer below article for details of reversed
# https://www.geeksforgeeks.org/reverse-string-python-5-different-ways/
result = list(filter(lambda x: (x == "".join(reversed(x))), my_list))

# printing the result
print(result)

Output :

['geeg', 'keek', 'aa']

Given a list of strings and a string str, print all anagrams of str

# Python Program to find all anagrams of str in
# a list of strings.
from collections import Counter

my_list = ["geeks", "geeg", "keegs", "practice", "aa"]
str = "eegsk"

# use anonymous function to filter anagrams of x.
# Please refer below article for details of reversed
# https://www.geeksforgeeks.org/anagram-checking-python-collections-counter/
result = list(filter(lambda x: (Counter(str) == Counter(x)), my_list))

# printing the result
print(result)

Output :

['geeks', 'keegs']