Python map to apply function to each element of an iterable like list, tuple,set

By using map we can apply function to each item of any iterable

map(function,iterable)

function can be built in or user defined
iterable can be list, tuple , set etc.

Using built-in function

String function len returns length of a string.

my_list=['Alex','Ronald','John']
my_list1=map(len,my_list) # using built in function len 
print(list(my_list1))

Output

[4, 6, 4]

Using user defined function

The function my_function will add 5 and return to each number it receives.

MATH=[20,30,40]
def my_function(n):
    return n+5
my_list1=map(my_function,MATH)
print(list(my_list1))

Output

[25, 35, 45]

Using lambda with map()

Sometime our function may require one input parmeter.

MATH=[20,30,40]
def my_function(n):
    return n+5

my_list1=map(lambda n:my_function(n),MATH)
print(list(my_list1))

Using Multiple iterators

We can get sum of three subjects

MATH=[20,30,40]
ENGLISH=[30,40,50]
SCIENCE=[40,50,60]
def my_function(a,b,c):
    return a+b+c
my_list1=map(my_function,MATH,ENGLISH,SCIENCE)
print(list(my_list1))

Output

[90, 120, 150]

Creating string from list

Here before using join() we can convert all elements to string by using str. We will apply map() to all elements to convert them to string.

my_list=['You','have','to','pass','in',3,'languages']
my_str = ' #'.join(map(str,my_list)) # from list create string
print(my_str)

When the required output is a list, a list comprehension can also be used to transform each item of an iterable.

list tuple Python- Tutorials

Subhendu Mohapatra

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map function

Using built-in function

Using user defined function

Using lambda with map()

Using Multiple iterators

Creating string from list

Subhendu Mohapatra