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Understanding the Python Map Function

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Ohidur Rahman Bappy

MAR 22, 2025

Understanding the Python map() Function

The map() function is a built-in utility in Python that allows you to apply a specified function to each item of an iterable (e.g., strings, lists, tuples, or dictionaries) and returns an iterable map object with the results.

map() Function Signature

map(function, iterable [, iterable2, iterable3,...iterableN]) --> map object

Example with a Simple Function

Consider the following simple square function:

def square(x):
    return x*x

Now, we can use the map() function to apply this square function to a list of numbers:

>>> numbers = [1, 2, 3, 4, 5]
>>> sqr_list = map(square, numbers)
>>> list(sqr_list)
[1, 4, 9, 16, 25]

In this example, the map() function applies the square function to each element in the numbers list, returning a map object that can be converted to a list of results.

Using map() with Lambda Expressions

The map() function can also be used with lambda functions, providing a convenient way to use small anonymous functions:

>>> sqr_list = map(lambda x: x*x, [1, 2, 3, 4, 5])
>>> list(sqr_list)
[1, 4, 9, 16, 25]

Utilizing map() with Built-in Functions

You can apply built-in functions using map(). Below is an example using the pow() function to map two list objects:

>>> bases = [10, 20, 30, 40, 50]
>>> indices = [1, 2, 3, 4, 5]
>>> powers = list(map(pow, bases, indices))
>>> powers
[10, 400, 27000, 2560000, 312500000]

In this example, pow() is used to raise each number in bases to the power of the corresponding number in indices, resulting in a list of computed powers.

Tags

python