Python map() function

map() function in Python applies a given function to each element of an iterable (list, tuple, set, etc.) and returns a map object (iterator). It is a higher-order function used for uniform element-wise transformations, enabling concise and efficient code.

Let's start with a simple example of using map() to convert a list of strings into a list of integers.

[1, 2, 3, 4]

Explanation: map() applies int() to each element in 's' which changes their datatype from string to int.

Syntax

map(function, iterable,..)

Parameters:

• function: The function to apply to every element of the iterable.
• iterable: One or more iterable objects (list, tuple, etc.) whose elements will be processed.

Note: You can pass multiple iterables if the function accepts multiple arguments.

Converting map object to a list

By default, map() function returns a map object, which is an iterator. In many cases, we will need to convert this iterator to a list to work with the results directly.

Example: Let's see how to double each element of the given list.

[2, 4, 6, 8]

Explanation:

• map(double, a) applies double() to each element in 'a'.
• list() converts the map object to a list.

map() with lambda

We can use a lambda function instead of a custom function with map() to make code shorter and easier. Let's see how to improve above code for better readability.

[1, 4, 9, 16]

Explanation:lambda x: x ** 2 squares each number and the results are converted into a list.

map() with multiple iterables

We can use map() with multiple iterables if the function we are applying takes more than one argument.

Example: In this example, map() takes two iterables (a and b) and applies lambda function to add corresponding elements from both lists.

[5, 7, 9]

Explanation: map() takes x from 'a' and 'y' from b and adds them.

Converting strings to Uppercase

This example shows how we can use map() to convert a list of strings to uppercase.

['APPLE', 'BANANA', 'CHERRY']

Explanation:str.upper method is applied to each element in the list fruits using map(). The result is a list of uppercase versions of each fruit name.

Extracting first character from strings

In this example, we use map() to extract the first character from each string in a list.

['a', 'b', 'c']

Explanation: lambda s: s[0] extracts first character from each string in the list words. map() applies this lambda function to every element, resulting in a list of the first characters of each word.

Removing whitespaces from strings

In this example, We can use map() to remove leading and trailing whitespaces from each string in a list.

['hello', 'world', 'python']

Explanation:str.strip method removes leading and trailing whitespaces from each string in list strings. map() function applies str.strip to each element and returning a list of trimmed strings.

Calculate fahrenheit from celsius

In this example, we use map() to convert a list of temperatures from Celsius to Fahrenheit.

[32.0, 68.0, 98.6, 212.0]

Explanation:

• lambda c: (c * 9/5) + 32 converts each Celsius temperature to Fahrenheit using standard formula.
• map() function applies this transformation to all items in the list celsius.