Python Map() Function

Last Updated on April 25, 2023 by Prepbytes

After applying the given function to each item of a given iterable, the Python Map function has the unique capability of returning a map object as a result. And that map object can easily be changed into a list, tuple, set dictionary, or string according to our requirements. Python map function is generally used for changing data types that are stored in an iterable object like a list, tuple, dictionary, or set.

What is the Python Map Function?

The Python map() method applies a function to each item of an iterator that is provided as input. For instance, an iterator can return an iterable map object and be a list, tuple, set, dictionary, or string. Map() is a built-in function in Python.

Syntax:

map(function, iterator1,iterator2 ...iteratorN)

Parameters
Majorly there are two parameters that are required to use the map function in Python.

• Function: It is necessary to provide a map with a function that will be applied to all of the iterator’s available items.
• Iterator: A mandatory iterable object. It could be a list, tuple, etc. The map() function accepts multiple iterator objects as arguments.

Return Value
The python map function will apply the specified function to every item in the iterator and return an iterable map object, such as a list, tuple, or other data structure.

How does the Python Map Function Work?

The iterable object and a function are the two inputs for the map() function. The function passed to map() is a standard function, and it will loop through each value in the supplied iterable object.

Consider, for instance, that you want to determine the square of each integer in a list of numbers.

• We require the function that returns the square of the input in order to obtain the result. The job will involve the following:

  def square(n):
      return n*n

• The following is a list of the things we wish to locate the square for:

  my_list = [2,3,4,5,6,7,8,9]

• Let’s now utilise the built-in map() Python method to get the square of each item in my list.

  Here is the final code:

  def square(n):
      return n*n
  my_list = [2,3,4,5,6,7,8,9]
  updated_list = map(square, my_list)
  print(updated_list)
  print(list(updated_list))

  Output:

  [4, 9, 16, 25, 36, 49, 64, 81]

  • A map object at 0x0000002C59601758 is presented on the screen as the map() function’s result, as seen in the output.
  • To obtain the desired result, you must use a for-loop or the list() method to iterate the map’s output. In the code that displays the values inside the provided list, I’ve used list().
  • Consequently, we are able to obtain the square of each number using the map() function.

Map was given the following list: [2,3,4,5,6,7,8,9] and after applying the square() function, the output of map() was [4, 9, 16, 25, 36, 49, 64, 81].

All of the entries in the list are subject to the square() function thanks to the python map function. For instance, my_list variable updates the list with each number’s square. The updated_list variable holds the out.

Using Python Map Function with Built-in Functions

Python map function as a built-in function can be used with other built-in functions. We’ll use the built-in Python round() method in the example to round the supplied values.

Example:
I have a list called my_list = [2.6743,3.63526,4.2325,5.9687967,6.3265,7.6988,8.232,9.6907] .

Each item’s rounded value from the list must be provided. Round() will be used as the function to map().

my_list = [2.6743,3.63526,4.2325,5.9687967,6.3265,7.6988,8.232,9.6907]
updated_list = map(round, my_list)
print(updated_list)
print(list(updated_list))

Output:

The list is processed by the round() function, which rounds all of the elements values as displayed in the output.

Using Python Map Function with a String as an Iterator

Python map function can also be used on a string. Since a string in Python functions like an array, using it inside the map() is simple.

The function myMapFunc() in the example takes care of changing the provided string to uppercase. The map() method receives the function myMapFunc(). By sending the string to myMapFunc(), the map function will handle changing the given string to uppercase.

Code Implementation

def myMapFunc(s):
    return s.upper()
my_str = "welcome to prepbytes!"
updated_list = map(myMapFunc, my_str)
print(updated_list)
for i in updated_list:
    print(i, end="")

Using Python Map Function with List of Numbers

Each number in the list will be multiplied by 10 in order to deal with the list in map().

We will use the following list: [2,3,4,5,6,7,8,9]. The function myMapFunc() handles multiplying 10 to the integer provided. Along with the list, the function for mapping is provided.

Code Implementation:

def myMapFunc(n):
    return n*10

my_list = [2,3,4,5,6,7,8,9]

updated_list = map(myMapFunc, my_list)
print(updated_list)
print(list(updated_list))

Each number in the list has been multiplied by 10 in the result that is visible.

Using Python Map Function with Tuple

Python objects with items surrounded in round brackets and separated by commas are known as tuples. We’ll use a tuple containing string values in the example. The function we’ll employ will change the values from lowercase to uppercase.

Code Implementation:

def myMapFunc(n):
    return n.upper()

my_tuple = ('php','java','python','c++','c')

updated_list = map(myMapFunc, my_tuple)
print(updated_list)
print(list(updated_list))

The result is a tuple that has all the values changed to uppercase.

Using Python Map Function with Dictionary

Curly brackets({}) are used to generate a dictionary in Python. You can use the dictionary inside the map() function because it is an iterator. Now let’s use the map() function’s dictionary as an iterator.

The following example demonstrates how the dictionary iterator in a map() operates

def myMapFunc(n):
    return n*10
my_dict = {2,3,4,5,6,7,8,9}
finalitems = map(myMapFunc, my_dict)
print(finalitems)
print(list(finalitems))

Using Python Map Function with Set

Set in Python is an unordered collection of items in curly brackets(()). Since set() is also an iterator, you can make use of it inside map() function.

Here is a working example of using set as an iterator inside map()

def myMapFunc(n):
    return n*10
my_set = {2,3,4,5,6,7,8,9}
finalitems = map(myMapFunc, my_set)
print(finalitems)
print(list(finalitems))

Using Python Map Function with the Lambda Function

A set in Python is a group of elements enclosed in curly brackets ({}). You can use set() inside the map() function because it is also an iterator.

Here is a working illustration of how to use the set inside of map() as an iterator.

Code Implementation

def myMapFunc(n):
    return n*10
my_set = {2,3,4,5,6,7,8,9}
finalitems = map(myMapFunc, my_set)
print(finalitems)
print(list(finalitems))

Using Multiple Iterators inside Python Map Function

Here, we will see multiple iterators inside the python map function using a single function inside it.

• Example 1: Passing two list iterators in the python map function
• You can send multiple iterators, such as a list, a tuple, etc., to the map() function at once.
• Suppose you want to add two lists, for instance. Using the map() function, the same thing is possible. my_list1 and my_list2 are the two lists we will employ.
• The first item in my_list1 is added to the first item in my_list2 in the example below. MyMapFunc() accepts elements from my_list1 and my_list2 and returns their sum.
• Here is a working example of using the map() method to combine two lists.

Code Implementation

def myMapFunc(list1, list2):
    return list1+list2

my_list1 = [2,3,4,5,6,7,8,9]
my_list2 = [4,8,12,16,20,24,28]

updated_list = map(myMapFunc, my_list1,my_list2)
print(updated_list)
print(list(updated_list))

Example 2: Passing one Tuple and a list iterator in the python map function
In the map() function, we’ll utilize a list and a tuple iterator. The function is passed to the map; myMapFunc() will retrieve the list and tuple items. An underscore(_) will be used to join the items. The working illustration is displayed below.:

def myMapFunc(list1, tuple1):
    return list1+"_"+tuple1

my_list = ['a','b', 'b', 'd', 'e']
my_tuple = ('PHP','Java','Python','C++','C')

updated_list = map(myMapFunc, my_list,my_tuple)
print(updated_list)
print(list(updated_list))

Output:

Conclusion

• The built-in method map() in Python applies a function to each item in an input iterator. An iterator returns an iterable map object and can, for instance, be a list, a tuple, a string, etc.
• The map() method will apply the specified function to each item in the iterator and produce a tuple, list, or other iterable map object.
• The built-in map() function in Python can be used with other built-in functions to create new functions.
• Python objects with items surrounded in round brackets and separated by commas are known as tuples. A tuple with string values will be used in the example. The function we’ll employ will change the values from lowercase to uppercase.
• Curly brackets({}) are used to generate a dictionary in Python. You can use the dictionary inside the map() function because it is an iterator.
• A set in Python is a group of elements enclosed in curly brackets (()). You can use set() inside the map() function because it is also an iterator.
• In Python, anonymous functions are created using lambda expressions (also known as lambda forms). Therefore, if you wish to utilise lambda inside the map, you must use the lambda keyword ().
• You can use the map() function to communicate several iterators, such as a list or tuple.

FAQ related to Python Map Function

Q1. What does map () function do?
Ans. For each item in an iterable, the map() function calls a predefined function. The object is passed as a parameter to the function.

Q2. What is an iterator in Python?
Ans. An iterator in Python is an object that enables iteration through data collections like lists, tuples, dictionaries, and sets.

Q3. What is filter () in Python?
Ans. Python includes a built-in function called filter(). An iterable, like a list or dictionary, can have the filter function applied to it to create a new iterator. Based on the criteria you supply, this new iterator can filter out specific elements quite well.

Q4. What is zip in Python?
Ans. With the zip() method in Python, you may build an iterator that combines elements from multiple iterables.