CODEWITHSUNDEEP
pythonrecursion
mista619
mista619

Reputation: 11

No result returned during recursion

So I was creating a simple recursive function which essentially compares two strings, 'string' and 'target', and if they're the same, the function replaces the 'target' with 'rep', much like the function of find and replace you would see in a text editor. My issue is, is that the function returns nothing. Is that because it hasn't hit my base case or am I missing an extra return somewhere?

def helperfn(string,target,rep,x): # x is always initially set to zero
    if x==len(string): #base case
        target=rep
        return target
    if len(string)==len(target):
        if string[x]==target[x]:
            helperfn(string,target,rep,(x+1))
    else:
         return "string and target are not the same"

A few examples of what the expected output should be:

helperfn("noway","noway","yes",0)=>"yes"
helperfn("ok","ok","never",0)=>"never"

Upvotes: 0

Views: 35

Answers (2)

Brian Besmanoff
Brian Besmanoff

Reputation: 31

When you call the function recursively, you want to return that value.

return helperfn(string,target,rep,(x+1))

Upvotes: 3

Yu Hao
Yu Hao

Reputation: 122383

It's because you never returned anything explicitly in one branch. Change

if len(string)==len(target):
    if string[x]==target[x]:
        helperfn(string,target,rep,(x+1))

to

if len(string)==len(target):
    if string[x]==target[x]:
        return helperfn(string,target,rep,(x+1))

Upvotes: 1

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