Python Map, Filter, and Reduce

Map Function:

Python map function is used to return the new list from another list ,this accepts another function and a sequence of ‘iterables’  as parameter  and returns the resulting sequence after applying the function to each iterable .

Syntax:

map(func, iterables)

Example:

list_1=(1, 2, 3, 4)
res=map(lambda x: x**2, numbers)
print(list(res))

Output: [1, 4, 9, 16]

Filter Function: 

In Python, filter function is a built-in function which is used to returns  an iterator were the each element in a sequence is filtered through a function to test if it satisfy a given condition or not.

Syntax:

filter(function, iterable)

Example:

def func_1(var):
    vowels = ['a', 'e', 'i', 'o', 'u']
    if (var in vowels):
        return True
    else:
        return False
  
  
# sequence
list_1 = ['p', 'y', 't', 'h', 'o', 'n', 'p', 'r','o','g','r','a','m']
  
# using filter function
filtered = filter(func_1, list_1)
  
print('The filtered letters are:')
for x in filtered:
    print(x)

Output:

The filtered letters are:
o
o
a

Reduce Function :

In Python, reduce() function is defined in the functools module. It is used to apply a particular function passed in its argument to all of the list elements mentioned in the sequence passed along.

Syntax:

reduce(func, iterable ,[initial])

Example:

from functools import reduce
def func_1(a,b):
    return a*b

res=reduce(func_1, range(1,10))
print ('Factorial of 9: ', res)

Output: Factorial of 9: 362880