{"id":247,"date":"2020-10-05T06:01:43","date_gmt":"2020-10-05T06:01:43","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=247"},"modified":"2025-03-26T12:44:12","modified_gmt":"2025-03-26T12:44:12","slug":"python-recursive-functions","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-basics\/python-recursive-functions\/","title":{"rendered":"Python Recursive Functions"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about Python recursive functions and how to use them to simplify your code.<\/p>\n\n\n\n

Introduction to recursive functions #<\/a><\/h2>\n\n\n\n

A recursive function is a function<\/a> that calls itself until it doesn’t.<\/p>\n\n\n\n

The following fn()<\/code> function is a recursive function because it has a call to itself:<\/p>\n\n\n

def<\/span> fn<\/span>()<\/span>:<\/span>\n    # ...<\/span>\n    fn()\n    # ...<\/span>\n<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In the fn()<\/code> function, the #...<\/code> means other code.<\/p>\n\n\n\n
def<\/span> fn<\/span>()<\/span>:<\/span>\n    # ...<\/span>\n    if<\/span> condition:\n        # stop calling itself<\/span>\n    else<\/span>:\n        fn()\n    # ...<\/span>\n<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Typically, you use a recursive function to divide a big problem that’s difficult to solve into smaller problems that are easier to solve.<\/p>\n\n\n\n
In programming, you’ll often find the recursive functions used in data structures and algorithms like trees, graphs, and binary searches.<\/p>\n\n\n\n
Python recursive function examples #<\/a><\/h2>\n\n\n\n
Let’s take some examples of using Python recursive functions.<\/p>\n\n\n\n
A simple recursive function example in Python #<\/a><\/h3>\n\n\n\n
Suppose you need to develop a countdown function that counts down from a specified number to zero.<\/p>\n\n\n\n
For example, if you call the function that counts down from 3, it’ll show the following output:<\/p>\n\n\n
3<\/span>\n2<\/span>\n1<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The following defines the count_down()<\/code> function:<\/p>\n\n\n
def<\/span> count_down<\/span>(start)<\/span>:<\/span>\n    \"\"\" Count down from a number  \"\"\"<\/span>\n    print(start)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
If you call the count_down()<\/code> function now:<\/p>\n\n\n
count_down(3<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
…it’ll show only the number 3.<\/p>\n\n\n\n
To show the numbers 3, 2, and 1, you need to:<\/p>\n\n\n\n
Additionally, a recursive function needs to have a condition to stop calling itself. So you need to add an if statement<\/a> like this:<\/p>\n\n\n