Python sys.setrecursionlimit() method



The Python sys.setrecursionlimit() method is used to set the maximum depth of the Python interpreter stack to a specified limit. This is useful when dealing with recursive functions as Python's default recursion limit is relatively low i.e. usually 1000 which can cause a RecursionError for deep recursions.

By increasing the recursion limit using sys.setrecursionlimit(limit) we allow deeper recursions to occur without hitting the limit though it should be used with caution since excessively deep recursion can lead to a stack overflow and crash the program. Properly managing recursion depth is crucial to avoid infinite recursion and system instability.

Syntax

Following is the syntax and parameters of Python sys.setrecursionlimit() method −

sys.setrecursionlimit(limit)

Parameter

This method accepts an integer value that representing the new recursion limit.

Return value

This method does not return any value.

Example 1

Following is the example showing that the recursion limit is increased from the default 1000 to 2000 by allowing the recursive function to handle deeper recursions without triggering a RecursionError −

Open Compiler
import sys # Default recursion limit print(sys.getrecursionlimit()) # Set a new recursion limit sys.setrecursionlimit(2000) print(sys.getrecursionlimit()) # Example of a recursive function def recursive_function(n): if n == 0: return 0 else: return 1 + recursive_function(n - 1) try: print(recursive_function(1500)) except RecursionError: print("Recursion limit exceeded")

Output

1000
2000
1500

Example 2

This example shows how to handle functions that require deeper recursion with the help of sys.setrecursionlimit() method −

Open Compiler
import sys # Function with deep recursion def deep_recursion(n): if n == 0: return "Reached the end" else: return deep_recursion(n - 1) # Try with default recursion limit try: print(deep_recursion(1500)) # Likely to raise RecursionError except RecursionError: print("RecursionError with default limit") # Set a higher recursion limit sys.setrecursionlimit(2000) # Try again with higher limit try: print(deep_recursion(1500)) # Should work without error except RecursionError: print("RecursionError even with higher limit")

Output

RecursionError with default limit
Reached the end

Example 3

This example calculates the factorial of a large number showing the need to increase the recursion limit to handle large recursive computations −

Open Compiler
import sys # Factorial function with recursion def factorial(n): if n == 0: return 1 else: return n * factorial(n - 1) # Default recursion limit is usually sufficient try: print(factorial(995)) # Should work fine except RecursionError: print("Recursion limit exceeded") # Increase recursion limit to handle larger inputs sys.setrecursionlimit(1500) try: print(factorial(1200)) # Should work now with increased limit except RecursionError: print("Recursion limit exceeded even with higher limit")

Output

4064374293729118100717076205049963163696947795811066648039580324660695257469883785154417906181986826077637
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0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
python_modules.htm
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