Fundamentals of Python Programming

Python reduce() function

Board Infinity
Board Infinity
Python reduce() function

    A-Z about Python Variables

    Python data Types

    String Concatenation in Python

    String formatting in Python

    Python print() Function

    Everything you need to know about Strings in Python

    Not Equal Operator in Python

    How to sort string in Python?

    Python For Loop

    Python While Loop

    Everything You Need to Know About Tuples in Python | Data Science

    Learn Different Methods to convert a List into a Tuple in Python

    List Slicing in Python

    Converting String to Float in Python

    List Index Out of Range Error in Python

    Python Sort() Function

    Python 2D Array

    How to Remove Key from Python Dictionary?

    Python dictionary values()

    Converting String to Dictionary in Python

    Bytes to String in Python

    Python reduce() function

    What are defaultdict in Python?

    Generators in Python

    Learn about range() in Python

    Python numpy.linspace()

    Exit Command in Python

    Python Virtual Environment

Introduction

A function and an iterable (such as a list, tuple, dictionary, etc.) are sent to Python's reduce() method to perform functional computing. The function returns the result after the calculation is complete (applying the function on the iterable).

The functools module in Python defines the reduce() method, which only delivers a single value as output after reducing the entire iterable to a single integer, string, or boolean. It does not return any iterators or multiple values. Let us understand what a reduce function in Python is.

reduce() Function: What is It?

Python's reduce() function applies a pre-defined function to each element of an iterable (such as a list, tuple, dictionary, etc.) and generates a single-valued result. Applying the reduce function to the iterable passed as an argument yields this single-valued output, which only returns a single integer, string, or boolean.

Without explicitly programming For loops, processing iterables using reduce() is very convenient. Reduce() is a built-in function written in the C programming language, making it much more optimized and faster. It is similar to a for loop in Python.

The functools module, which must be imported before calling the function in our program, contains the reduce() function in Python. This single value output denotes that only one integer, string, or boolean is returned due to applying the reduce function to the iterable. Let us look at the syntax of reduce function in Python.

Syntax

functools.reduce(function, iterable)

These two parameters in reduce function are

  • Reduce() takes a function as its first argument. The result will be computed cumulatively, applying this function to each element in an iterable.
  • The second argument can be repeated. Python objects that can be iterated over or looped over are known as iterables. Examples include lists, tuples, sets, dictionaries, generators, iterators, etc.

Let us look at the working of reduce function in Python.

Working of Reduce Function in Python

The reduce() function in the functools module of Python only returns one value and doesn't return any other values. Steps for using Python's reduce function are mentioned below:

  1. The iterable's first two elements are subject to the function passed as an argument.
  2. The function is then applied to both the most recent result that was generated and the subsequent element in the iterable.
  3. The iterable is processed until the end of this process.
  4. Applying the reduce function to the iterable causes the single value to be returned.

Let us look at the example of reduce function in Python.

Examples

We will discuss different examples by using reduce() function in Python.

Lamba Function with Reduce Function

In the given example, a lambda function has been defined to use the reduce function to iteratively calculate the multiplication of two numbers on the passed list.

from functools import reduce

myNumbs = [1, 2, 3, 4]
res = reduce(lambda a, b: a * b, myNumbs)
print(res)

Output

24

write your code here: Coding Playground

Predefined Function with Reduce Function

Now, a pre-defined function called sum is used as an argument in the reduce() function, that is passed a list of numbers and returns the sum of any two numbers that are passed to it.

from functools import reduce
# calculates the sum of two elements

def sum(a,b):
    return a+b

res = reduce(sum, [2, 5, 3, 7])
print(res)

Output

17

write your code here: Coding Playground

Operator Function with Reduce Function

Operator functions and the reduce function are sometimes implemented together in Python. Operator functions are the fundamental pre-defined logical, bitwise, and mathematical operations bundled into a single operator module in Python. Let's investigate the relationship between operator functions and the reduce function.

import functools
import operator

myNumbs = [-1, 8, 12, 6, 3]
# Using add operator
print("The sum using add operator function is", functools.reduce(operator.add, myNumbs))

# Using Concat operator
print(functools.reduce(operator.concat, ["Board ", "Infinity"]))

Output

The sum using add operator function is 28
Board Infinity

write your code here: Coding Playground

Let us understand how can we use reduce function in Python with three parameters.

reduce() Function with Three Parameters

In Python 3, the reduce function, or reduce(), supports both two and three parameters. To put it simply, reduce(), if it is present, places the third parameter before the value of the second one. The third argument then acts as the default one if the second argument is an empty sequence.

Code

from functools import reduce
myNumbs = (1, 5, 9, 19, 23)

# Using 3 Parameters
print(reduce(lambda a, b: a+b, myNumbs, 4))

Output

61

write your code here: Coding Playground

Conclusion

Python's Reduce function enables us to apply reduction operations to iterables using lambda and callable functions. A function called reduce() reduces the elements of an iterable to a single cumulative value. The reduce function in Python solves various straightforward issues, including adding and multiplying iterables of numbers.

Even though many Python functions, such as sum(), any(), and min(), have largely replaced the Reduce function, it is still a very common technique in functional programming.