Python: Recursion only one output

Question

I wanted to write a recursive function to fit curves. For some reasons my results didn't looked good so I boiled down the problem to one easy example:

Number = 6
Successor = 0

def Fuction(Number, Successor):
    if (Number - Successor)+1>0:
       Successor += 1
       Fuction(Number, Successor)
    else:
        return(Fuction(Number, Successor))


A = Fuction(Number, Successor) 
print(f'The Successor of {Number} is {A}')

When I do this the Kernel dies. How can I fix it? (I followed the awnser : Why does my recursive function return none)

"The kernel dies" -- yikes! Are you sure this isn't just the CPython interpreter gently raising an error? What output are you expecting here and why use recursion at all? — ggorlen
– ggorlen, Commented Jun 2, 2021 at 15:17
Why are you calling Fuction() again in the if (Number - Successor) + 1 > 0 branch? When do you expect this function to stop recurring, and what is it supposed to return in that branch? — Green Cloak Guy
– Green Cloak Guy, Commented Jun 2, 2021 at 15:17
I expect this function to stop recurring if "Successor = Number + 1". Again this is an abstract version of my real problem. I just want to know how I can use the return function such that the output reads: "The Successor of 6 is 7" — Phicalc
– Phicalc, Commented Jun 2, 2021 at 15:21
I'm afraid to ask, but why not do 6 + 1? The problem here should be pretty clear by stepping with a debugger or adding a print. Your base case is supposed to be the else branch. "Base case" means "stop the recursion", yet you do return(Fuction(Number, Successor)) in this branch, continuing the recursion infinitely. You can just return Successor, then your problem reduces to the link you provided because the recursive branch isn't returning anything. As an aside, only classes should start with uppercase letters. The convention is to use lower-case for vars. — ggorlen
– ggorlen, Commented Jun 2, 2021 at 15:25
Again: This is an abstract version of my real problem. I want to create a recursive function to fit data (without using lmfit whatsoever). I want my output not just to be something I print but something I can use in my code later. When I return successor, I get the awnser 'none' when it's in the else block, or the awnser 'the successor of 6 is 1' — Phicalc
– Phicalc, Commented Jun 2, 2021 at 15:40

Milos Stojanovic · Accepted Answer · 2021-06-02 15:33:11Z

1

Maybe something like this?

Number = 6
Successor = 0

def Fuction(Number, Successor):
    if (Number - Successor) + 1 == 0: # base case for interrupting recursion
        return Successor
    Successor += 1
    return Fuction(Number, Successor)

A = Fuction(Number, Successor) # will be 7
print(f'The Successor of {Number} is {A}')

You can also do it like this which is more similar to your code example:

def Fuction(Number, Successor):
    if (Number - Successor) + 1 > 0:
        Successor += 1
        return Fuction(Number, Successor)
    return Successor

answered Jun 2, 2021 at 15:33

Milos Stojanovic

1,1421 gold badge9 silver badges23 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Dharman · Accepted Answer · 2021-06-02 16:02:14Z

0

The problem here is that the recursion does not terminate. The issue occurs when Number=6 and Successor=7, Fuction(6,7) just calls Fuction(6,7) again and again until the interpreter crashes due its recursion limit being exceeded. I believe this is when your kernel dies.

The solution here is to find the right base case for the recursion where it can return without making another recursive call.

Here's a nice video explaining how to implement recursion.

edited Jun 2, 2021 at 16:02

Dharman♦

33.9k27 gold badges106 silver badges157 bronze badges

answered Jun 2, 2021 at 15:56

Abhilash

1994 silver badges14 bronze badges

Collectives™ on Stack Overflow

Python: Recursion only one output

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related