{"id":20053,"date":"2020-07-24T02:06:13","date_gmt":"2020-07-24T09:06:13","guid":{"rendered":"https:\/\/careerkarma.com\/blog\/?p=20053"},"modified":"2023-12-01T03:56:01","modified_gmt":"2023-12-01T11:56:01","slug":"python-recursion","status":"publish","type":"post","link":"https:\/\/careerkarma.com\/blog\/python-recursion\/","title":{"rendered":"Python Recursion: A Guide"},"content":{"rendered":"\n

How to Use Python Recursion<\/h2>\n\n\n\n

Python recursion is an intimidating topic for beginners. Let\u2019s dispel the myth that recursion is difficult by defining it. Recursion is a method of programming where a function calls itself.
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That sounds simple, right? When you get the hang of it, recursion is not a difficult concept.
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In this Python tutorial, we\u2019re going to talk about recursion and how it works. We\u2019ll walk through an example of recursion using factorial functions to help you get started with this method of programming.<\/p>\n\n\n\n

What is Recursion?<\/h2>\n\n\n\n

Recursion is where you define something in terms of itself.
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A recursive function solves problems by calling itself over again. This behavior is supported in most major programming languages, such as Python. They are a crucial part of computer science and data science.
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Recursion is useful when the solution to a problem can be found by breaking it down into smaller problems which all use the same formula. These types of problems are often called \u201crecursive algorithms.\u201d The key to solving them is in the name!<\/p>\n\n\n\n

Iterative vs. Recursive<\/h2>\n\n\n\n

There are two ways to solve an algorithm: iteratively or recursively.
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Iterative solutions to algorithms are regarded as \u201cpowerful but ugly.\u201d They get the job done, but they don\u2019t exactly do it in the most elegant way. To properly understand recursive algorithms, we need to look at iterative functions.
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An iterative function<\/a> is a function that solves a problem using a loop. It will execute the code inside a loop until that loop is complete. A recursive function is a function that breaks a problem down into smaller parts and solves each part by calling itself.<\/p>\n\n\n\n

Factorials: The Iterative Example<\/h2>\n\n\n\n

Factorials are a good way to demonstrate recursion and iterative thinking. In math, factorials are the sum of a number and every number before it multiplied together.
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The factorial of 5 is equal to 5 * 4 * 3 * 2 * 1. The factorial of 2 is equal to 2 * 1.
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To calculate a factorial, we can write an iterative function:<\/p>\n\n\n\n

def factorial(number):\n\ttotal = 1\n\tfor n in range(1, number + 1):\n\t\ttotal = total * n\n\treturn total<\/pre><\/div>\n\n\n\n
This function uses a for loop<\/a> to iterate through all numbers in the range<\/a> of 1 and the number we have specified plus 1. For each iteration, the number the loop is iterating over is multiplied by the total. Let\u2019s call our function to find the factorial:
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answer = factorial(4)\nprint(answer)<\/pre><\/div>\n\n\n\n
Our code returns: 24. To arrive at this solution, our code runs:<\/p>\n\n\n\n