Hello everyone In this article, I will introduce you to the concept of Thread Rules in Python. You all find out in my article!
What is recursion?
Recursion means that a function calls itself back.
An example of t is to place two parallel mirrors facing each other. Any object in between them will be reflected called recursion.
Recursive Functions in Python
In Python, we know that one function can call other functions. It is even possible for the function to call itself. These types of structures are called recursive functions.
The following image shows the operation of a recursive function called the recurse .
The following is an example of a recursive function to find the factorial of an integer.
The factorial of a number is the product of all integers between 1 and that number. Example: the factorial of 6 (denoted by 6!) Is 1*2*3*4*5*6 = 720
Example of a recursive function
1 2 3 4 5 6 7 8 9 10 11 12 13 | def factorial(x): """This is a recursive function to find the factorial of an integer""" if x == 1: return 1 else: return (x * factorial(x-1)) num = 3 print("The factorial of", num, "is", factorial(num)) |
The result will be
1 2 | The factorial of 3 is 6 |
In the example above factorial() is a recursive function because it calls itself.
When we call this function with a positive integer, it recursively calls itself by decrementing the number
Each function multiplies the number by the factorial of the number below it until it equals one. How to call this recursive function can be explained in the following steps.
1 2 3 4 5 6 7 | factorial(3) # 1st call with 3 3 * factorial(2) # 2nd call with 2 3 * 2 * factorial(1) # 3rd call with 1 3 * 2 * 1 # return from 3rd call as number=1 3 * 2 # return from 2nd call 6 # return from 1st call |
Here’s an image that explains step-by-step how to treat recursive functions:
Our recursion ends when the number drops to 1. This is called a mandatory condition.
Note that every recursive function must have a condition that is required to stop recursion otherwise the function calls itself indefinitely.
By default, the maximum depth of recursion is 1000 . If the limit is passed, it results in a RecursionError error.
Below is an example where the depth limit is exceeded.
1 2 3 4 | def recursor(): recursor() recursor() |
The error will display as follows:
1 2 3 4 5 6 7 8 | Traceback (most recent call last): File " <span class="token tag"><span class="token tag"><span class="token punctuation"><</span> string</span> <span class="token punctuation">></span></span> ", line 3, in <span class="token tag"><span class="token tag"><span class="token punctuation"><</span> module</span> <span class="token punctuation">></span></span> File " <span class="token tag"><span class="token tag"><span class="token punctuation"><</span> string</span> <span class="token punctuation">></span></span> ", line 2, in a File " <span class="token tag"><span class="token tag"><span class="token punctuation"><</span> string</span> <span class="token punctuation">></span></span> ", line 2, in a File " <span class="token tag"><span class="token tag"><span class="token punctuation"><</span> string</span> <span class="token punctuation">></span></span> ", line 2, in a [Previous line repeated 996 more times] RecursionError: maximum recursion depth exceeded |
Some advantages of Recursion
- When using the Recursive function, the code will be cleaned and optimized.
- A complex request can be broken down into smaller, simpler tasks using recursion.
Conclude
Below I have introduced you to the concept of Recursion in Python. If you have any questions, please leave a comment below.
See more details
https://www.programiz.com/python-programming/object-oriented-programming