This article will explain how to use recursion in Python functions, with some example code to illustrate the concept.
A recursive function is a function which calls itself one or more times until a condition is met.
If a function that uses recursion calls itself too many times, Python will throw an error.
As this is a demonstration of a code structure rather than anything with any specific syntax, I’ll show a simple example of a recursive function and leave comments explaining what is going on.
Python Recursion Example & Explanation
This example Python code illustrates a recursive function and includes some commentary explaining things:
# Defines a recursive function
# A single parameter is accepted - the count of how many times this function should call itself
def my_recursive_function(count):
# Define a variable to hold the result which is the current number of remaining times for the function to recur
result = count - 1
# If the result is greater than 0, there are still remaining recursions to run
if(result >= 0):
print(result)
# You could put any code here you want to be executed with each recursion
my_recursive_function(count - 1) # The function is calling itself for the next recursion. It is subtracting one from the count so that it doesn't recur infinitely
else:
# The recursion count has been reached, exit the function by returning the result
return result
print("Recursive Function Results:")
my_recursive_function(7) # This is where the function is called for the first time - from there it calls itself
Which will output:
Recursive Function Results: 6 5 4 3 2 1 0
In the above example, boolean operators are used to compare values in an if/else statement.
Recursive functions are not limited to updating variables within them and can update global variables for later use.
What Happens When There’s Too Much Recursion in Python
If your function calls itself too many times, you’ll see the following error generated by Python:
RecursionError: maximum recursion depth exceeded
By default, Python has a recursion limit of 1000.
If you find yourself having to use recursion to the degree that hits this limit, you may want to consider restructuring your code rather than raising that limit. Otherwise, you will find yourself running into performance issues.
One way to achieve this is to split your data into small chunks and deal with it in batches.
Nobody likes software that eats up all of their CPU/RAM.
