How do i remove a recursion error in python?
I have this tail recursive function here: Show
It works up to
asked Jul 23, 2010 at 23:04
14 It is a guard against a stack overflow, yes. Python (or rather, the CPython implementation) doesn't optimize tail
recursion, and unbridled recursion causes stack overflows. You can check the recursion limit with
and change the recursion limit with
but doing so is dangerous -- the standard limit is a little conservative, but Python stackframes can be quite big. Python isn't a functional language and tail recursion is not a particularly efficient technique. Rewriting the algorithm iteratively, if possible, is generally a better idea.
Rob Bednark 23.8k20 gold badges78 silver badges117 bronze badges answered Jul 23, 2010 at 23:08
Thomas WoutersThomas Wouters 127k23 gold badges146 silver badges122 bronze badges 10 Looks like you just need to set a higher recursion depth:
answered Jul 23, 2010 at 23:07
David YoungDavid Young 4,5432 gold badges20 silver badges18 bronze badges 2 It's
to avoid a stack overflow. The Python interpreter limits the depths of recursion to help you avoid infinite recursions, resulting in stack overflows. Try increasing the recursion limit ( From the Python documentation:
answered Jul 23, 2010 at 23:08
ScharronScharron 16.8k6 gold badges42 silver badges63 bronze badges 1 If you often need to change the recursion limit (e.g. while solving programming puzzles) you can define a simple context manager like this:
Then to call a function with a custom limit you can do:
On exit from the body of the P.S. You may also want to increase the stack size of the Python process for big values of the recursion limit. That can be done via the answered May 1, 2018 at 16:37
Eugene YarmashEugene Yarmash 135k37 gold badges309 silver badges367 bronze badges 2
The Linux kernel limits the stack of processes. Python stores local variables on the stack of the interpreter, and so recursion takes up stack space of the interpreter. If the Python interpreter tries to go over the stack limit, the Linux kernel makes it segmentation fault. The stack limit size is controlled with the Python offers access to those system calls through the
Example program: main.py
Of course, if you keep increasing From bash, you can see and set the stack limit (in kb) with:
The default value for me is 8Mb. See also:
Tested on Ubuntu 16.10, Python 2.7.12. answered Jan 28, 2017 at 23:40
3 Use a language that guarantees tail-call optimisation. Or use iteration. Alternatively, get cute with decorators. answered Jul 23, 2010 at 23:12
Marcelo CantosMarcelo Cantos 177k38 gold badges321 silver badges362 bronze badges 4 I realize this is an old question but for those reading, I would recommend against using recursion for problems such as this - lists are much faster and avoid recursion entirely. I would implement this as:
(Use n+1 in xrange if you start counting your fibonacci sequence from 0 instead of 1.) answered Sep 6, 2013 at 3:17
DanielDaniel 3,2145 gold badges26 silver badges35 bronze badges 6 I had a similar issue with the error "Max recursion depth exceeded". I discovered the error was being triggered by a corrupt file in the directory I was looping
over with
answered Oct 14, 2014 at 18:14
TylerTyler 1911 silver badge6 bronze badges 3 Of course Fibonacci numbers can be computed in O(n) by applying the Binet formula:
As the commenters note it's not O(1) but O(n) because of answered Oct 8, 2015 at 6:19
rwstrwst 2,4362 gold badges28 silver badges35 bronze badges 9 If you want to get only few Fibonacci numbers, you can use matrix method.
It's fast as numpy uses fast exponentiation algorithm. You get answer in O(log n). And it's better than Binet's formula because it uses only integers. But if you want all Fibonacci numbers up to n, then it's better to do it by memorisation. answered Feb 17, 2018 at 15:57
bebidekbebidek 5643 silver badges8 bronze badges 1 We can do that using
Output
Sourcefunctools lru_cache
answered Oct 26, 2019 at 15:26
EmmaEmma 26.9k10 gold badges41 silver badges65 bronze badges 2 As @alex suggested, you could use a generator function to do this sequentially instead of recursively. Here's the equivalent of the code in your question:
answered Jul 12, 2016 at 16:58
martineaumartineau 115k25 gold badges160 silver badges284 bronze badges RecursionError: maximum recursion depth exceeded in comparison Solution : First it’s better to know when you execute a recursive function in Python on a large input ( > 10^4), you might encounter a “maximum recursion depth exceeded error”. The sys module in Python have a function getrecursionlimit() can show the recursion limit in your Python version.
The default in some version of Python is 1000 and in some other it was 1500 You can change this limitation but it’s very important to know if you increase it very much you will have memory overflow error. So be careful before increase it. You can use setrecursionlimit() to increase this limitation in Python.
Please follow this link for more information about somethings cause this issue : https://elvand.com/quick-sort-binary-search/ answered Mar 17, 2021 at 16:33
Edit: 6 years later I realized my "Use generators" was flippant and didn't answer the question. My apologies. I guess my first
question would be: do you really need to change the recursion limit? If not, then perhaps my or any of the other answers that don't deal with changing the recursion limit will apply. Otherwise, as noted, override the recursion limit using Use generators?
Above
martineau 115k25 gold badges160 silver badges284 bronze badges answered Jul 30, 2015 at 18:32
alexalex 2272 silver badges6 bronze badges 3 Many recommend that increasing recursion limit is a good solution however it is not because there will be always limit. Instead use an iterative solution.
answered Apr 13, 2016 at 8:56
Harun ERGULHarun ERGUL 5,4645 gold badges53 silver badges60 bronze badges I wanted to give you an example for using memoization to compute Fibonacci as this will allow you to compute significantly larger numbers using recursion:
This is still recursive, but uses a simple hashtable that allows the reuse of previously calculated Fibonacci numbers instead of doing them again. answered Mar 12, 2019 at 13:59
eyllanesc 226k18 gold badges131 silver badges199 bronze badges answered May 7, 2019 at 5:35
1 We could also use a variation of dynamic programming bottom up approach
answered Nov 12, 2019 at 16:32
xariezxariez 5091 gold badge5 silver badges17 bronze badges I'm not sure I'm repeating someone but some time ago some good soul wrote Y-operator for recursively called function like:
and then recursive function needs form:
for Fibonacci numbers your function looks like this:
output:
(actually tones of digits) answered Dec 14, 2020 at 14:33
wiesiu_pwiesiu_p 5205 silver badges6 bronze badges How do you fix a recursion error in Python?Try increasing the recursion limit ( sys. setrecursionlimit ) or re-writing your code without recursion. Return the current value of the recursion limit, the maximum depth of the Python interpreter stack. This limit prevents infinite recursion from causing an overflow of the C stack and crashing Python.
How do I bypass recursion limit in Python?The recursion depth limit in Python is by default 1000 . You can change it using sys. setrecursionlimit() function.
What does recursion error mean in Python?A Python RecursionError exception is raised when the execution of your program exceeds the recursion limit of the Python interpreter. Two ways to address this exception are increasing the Python recursion limit or refactoring your code using iteration instead of recursion.
What does recursion error mean?In some ways, recursion is analogous to a loop. Both execute the same code multiple times, and both require a condition (to avoid an infinite loop, or rather, infinite recursion in this case). When there are too many function calls, or a function is missing a base case, JavaScript will throw this error.
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