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Python supports object-oriented programming and has a concise, readable, and easy-to-learn syntax. It is no wonder that it is one of the most popular programming languages. An integral part of Python are its built-in functions.
We've written a series of articles to help you learn and brush up on the most useful Python functions. In this article, we’ll learn about Python's reduce() function and how to use it.
Note that the function reduce() in Python was originally built-in, and still is, in 2.x versions. But in versions starting 3.0, it has been moved to functools due to readability and performance-related factors. We’ll learn more about reduce() and how to use it in this article.
If you are preparing for a tech interview, check out our technical interview checklist, interview questions page, and salary negotiation e-book to get interview-ready! Also, read Python String join() Method, Python Exit commands, and Type and Isinstance In Python for more content on Python coding interview preparation.
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The reduce() function in Python implements a mathematical technique called folding or reduction. This technique involves reducing a list of items to a single cumulative value. Python’s reduce() operates on any iterable. Also, for using reduce() in Python 3.x, reduce() needs to first be imported using an import statement to the current scope.
Python’s reduce() function takes an existing function and applies the function cumulatively to every item in the given iterable, and gives a single return value. Here’s how it works:
Let us now look at the syntax for reduce().
Syntax of reduce() In Python 3.x
Syntax of reduce() In Python 2.x and Earlier Versions
Here, we take a look at how you can use the Python function reduce() in Python 3.x next time you need it:
For Python 2.x, we can directly use reduce() without needing to import functools as can be seen in the example below:
Found this article helpful? You can learn about more Python functions in our learn folder.
Q1. What is reduce() in Python?
The reduce() function in Python implements a mathematical technique called folding or reduction and works by applying a function to an iterable and reducing it to a single cumulative value.
Q2. What does reduce function return in Python?
Facilitating a functional approach in Python, reduce() takes a function and an iterable as arguments and returns the final computed cumulative value.
Q3. Where in Python is reduce() located?
Starting Python 3.x, the reduce() function is defined and located in the functools module but is a built-in function in earlier versions like Python 2.x.
Q4. Is reduce a built-in function?
Python's reduce() function was originally a built-in function (and still is in Python 2. x), but it was moved to functools.
Q5. What arguments does the reduce() function take in Python?
The reduce() function takes two arguments in Python — function and an iterable.
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