RecursionError is an exception that occurs when the maximum recursion depth is exceeded. This typically occurs when a function calls itself recursively, and the recursion doesn't have a proper stopping condition (base case).
What Causes RecursionError
RecursionError in Python is caused by a function calling itself recursively without a proper base case. Python has a limit on the number of times a function can call itself recursively. This is to ensure that the function does not execute indefinitely. If this limit is exceeded by a recursive function, a
RecursionError is raised.
Python RecursionError Example
Here’s an example of a Python
RecursionError thrown when calling a recursive function that does not have a base case:
def func(): func() func()
Since the recursive function
func() does not have a terminating condition, calling it creates an infinite loop as the function keeps calling itself over and over again until the
RecursionError: maximum recursion depth exceeded error occurs:
Traceback (most recent call last): File "test.py", line 4, in <module> func() File "test.py", line 2, in func func() File "test.py", line 2, in func func() File "test.py", line 2, in func func() [Previous line repeated 996 more times] RecursionError: maximum recursion depth exceeded
How to Fix RecursionError in Python
Here are some approaches to fix a recursion error in Python:
- Adding a base case: The most common cause of a recursion error is that the function does not have a base case to stop the recursion. In such cases, a base case can be added to the function that stops recursion when a condition is met.
- Increasing the recursion limit: Python has a default maximum recursion depth of 1000. If a function exceeds this limit, it can be increased using the
sys.setrecursionlimit(n)function. Developers should be careful when increasing the limit as this can cause a crash if the recursion is not properly controlled.
- Using an iterative approach: If a recursive approach is causing a recursion error, it may be possible to use an iterative approach instead e.g. a
whileloop. This can reduce the risk of hitting the maximum recursion depth, and in some cases can also lead to more efficient and easier to understand code.
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