Python Map, Filter & Reduce Functions

Python Map Function

The map() function in Python is a built-in function that applies a function to each element of an iterable (such as a list, tuple, or string) and returns a new iterator with the transformed elements.

The map() function has the following syntax:

map(function, iterable)

This is an example of a list transformation using the map() function:

numbers = [1, 2, 3, 4, 5]
# Map (map(function, list))
# block of code to add 10 to each value in our list

result = map(lambda item: item + 10, numbers)
print(list(result))

The map() function is a convenient way to apply a function to many elements in an iterable. It is often used to transform or filter the elements of a list or other iterable object.

Python Filter Function

The filter() function in Python is a built-in function that takes an iterable and a function as input, and returns an iterator with the elements that return True when passed to the function.

The filter() function has the following syntax:

filter(function, iterable)

This is an example of a list transformation using the filter() function:

numbers = [1, 2, 3, 4, 5]
# Filter (filter(function, list))
# write a python code to filter the items that are divisible by 2

result = filter(lambda item: item % 2 == 0, numbers)
print(list(result))

The filter() function is a convenient way to select specific elements from an iterable based on a certain condition. It is often used to filter lists or other iterable objects to create new lists with only the elements that satisfy a certain criterion.

Python Reduce Function

The reduce() function in Python is a built-in function that applies a function to an iterable in a cumulative manner to reduce the iterable to a single value. It is a part of the functools module, so you need to import it before you can use it.

The reduce() function has the following syntax:

reduce(function, iterable, initializer=None)

The reduce() function is a function that takes in two arguments and returns a single value. The 'iterable' is an iterable object, such as a list, tuple, or string. The initializer is an optional argument that specifies an initial value to be used in the reduction. If the initializer is not provided, the reduce() function will use the first element of the iterable as the initial value.

This is an example of a list transformation using the reduce() function:

numbers = [1, 2, 3, 4, 5]
# Reduce (reduce(function, list))
# we use the reduce function to reduce a list into a single value

from functools import reduce

result = reduce(lambda a, b: a + b , numbers)
print(result)

The reduce() function is a useful tool for performing a cumulative operation on an iterable object. It can be used to perform a wide variety of tasks, such as calculating the sum or product of a list of numbers, finding the longest string in a list, or concatenating a list of strings.