(Python) RecursionError: maximum recursion depth exceeded

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Borislav Hadzhiev

Last updated: May 1, 2022

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(Python) RecursionError: maximum recursion depth exceeded #

The Python "RecursionError: maximum recursion depth exceeded" occurs when a function is being called so many times that the invocations exceed the recursion limit. To solve the error, specify a base case that has to be met to exit the recursion or set a higher recursion limit.

recursionerror maximum recursion depth exceeded

Here is an example of how the error occurs.

main.py
def example(): example() # ⛔️ RecursionError: maximum recursion depth exceeded example()

We call the function, which then calls itself until the recursion limit is exceeded.

You can get the current value of the recursion limit by using the sys.getrecursionlimit() method.

main.py
import sys # 👇️ 1000 print(sys.getrecursionlimit()) # 👇️ set recursion limit to 2000 sys.setrecursionlimit(2000) # 👇️ 2000 print(sys.getrecursionlimit())

The getrecursionlimit method returns the maximum depth of the Python interpreter stack.

You can use the setrecursionlimit method if you need to update this value.

To solve the error from the example, we have to specify a condition at which the function stops calling itself.

main.py
counter = 0 def example(num): global counter if num < 0: return # 👈️ this stops the function from endlessly calling itself counter += 1 example(num - 1) example(3) print(counter) # 👉️ 4

This time we check if the function was invoked with a number that is less than 0 on every invocation.

If the number is less than 0, we simply return from the function so we don't exceed the maximum depth of the Python interpreter stack.

If the passed in value is not less than zero, we call the function with the passed in value minus 1, which keeps us moving toward the case where the if check is satisfied.

A recursive function calls itself until a condition is met. If there is no condition to be met in your function, it will call itself until the maximum depth of the Python interpreter stack is exceeded.

You might also get this error if you have an infinite loop that calls a function somewhere.

ma
def do_math(a, b): return a + b while True: result = do_math(10, 10) print(result)
Our while loop keeps calling the function and since we don't have a condition that would exit the loop, we eventually exceed the interpreter stack.

This works in a very similar way to a function calling itself without a base condition.

Here's an example of how to specify a condition that has to be met to exit the loop.

main.py
def do_math(a, b): return a + b total = 0 i = 10 while i > 0: total += do_math(5, 5) i = i - 1 print(total) # 👉️ 100

If the i variable is equal to or less than 0, the condition in the while loop is not satisfied, so we exit the loop.

If you can't track exactly where your error occurs, look at the error message.

maximum recursion depth exceeded error message

The screenshot above shows that the error occurred on line 84 in the example() function.

You can also see that the error occurred in the main.py file.

Conclusion #

The Python "RecursionError: maximum recursion depth exceeded" occurs when a function is being called so many times that the invocations exceed the recursion limit. To solve the error, specify a base case that has to be met to exit the recursion or set a higher recursion limit.

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