How Can I Avoid RecursionError in Python's Recursive Functions?

Exceeding Recursion Depth and Mitigation Strategies

Python programmers commonly encounter stack overflows due to deep recursion. When the maximum recursion depth is exceeded, a RecursionError is raised. This occurs because Python's CPython implementation lacks tail recursion optimization.

Tail Recursive Function Example

Consider the following tail recursive function:

def recursive_function(n, sum):
    if n < 1:
        return sum
    else:
        return recursive_function(n-1, sum+n)

When called with n=998, the function fails with a RecursionError.

Increasing Recursion Limit

Python provides the sys.getrecursionlimit() function to retrieve the current recursion limit. By default, this limit is relatively low to prevent excessive stack consumption. To increase the limit, use sys.setrecursionlimit(new_limit).

Caution

Increasing the recursion limit is potentially hazardous. Python stackframes, which hold function call information, can be sizable. Excessively increasing the limit can exhaust available memory.

Iterative Alternative

As a preferred approach, try to rewrite the algorithm iteratively. Python is not inherently a functional language, and tail recursion may not be an efficient technique. Iterative solutions often perform better.

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