Replace input strings and integers

Question

I need to write a function that takes a string (str), and two other strings (call it replace1 and replace2), and an integer (n). The function shall return a new string, where all the string inputs from replace1 in the first string (str) and replace the new string with replace1 depending on where you want the new input. I am not supposed to use built-in functions, but I can use lens (we can suppose that replace1 has the length 1). Example ( call it replaceChoice):

>>> replaceChoice(“Mississippi”, “s”, “l”, 2)
'Mislissippi'

I hope that I explained it well. Here is my attempt:

def replaceChoice(str1, replace1,n): 
newString=""
  for x in str:
      if x=="str1":
        newString=newString+replace 
  else:
       newString=newString+x 
  return newString

What happens when you call your function as you've written it there? I suspect not much even if the indentation is fixed, because it'll error when it reaches newString=newString+replace because you don't pass replace as an argument — Andrew
– Andrew, Commented Sep 10, 2016 at 9:38
You also don't indicate explicitly what you use the integer argument n for, though it looks like it's the position you want to insert (i.e. your example should replace the second s in the string with the proposed character). Obvious homework is obvious. — Andrew
– Andrew, Commented Sep 10, 2016 at 9:39
@The_nice_doge you should accept the answer if it answers your question. — Pankaj Singhal
– Pankaj Singhal, Commented Sep 10, 2016 at 14:33

Pankaj Singhal · Accepted Answer · 2016-09-10 12:21:58Z

1

I assume from your question that you want to replace the nth occurrence of r1 with r2. Is this what you want?

>>> def replaceChoice(str1, r1, r2, n):
...     new_str = ""
...     replaced = False
...     for i in str1:
...             if i==r1:
...                     n-=1
...             if n==0 and not replaced:
...                     replaced = True
...                     new_str+=r2
...             else:
...                     new_str+=i
...     return new_str
... 
>>> replaceChoice("Mississippi", "s", "l", 2)
'Mislissippi'

edited Sep 10, 2016 at 12:21

answered Sep 10, 2016 at 9:44

Pankaj Singhal

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2 Comments

Rolf of Saxony Over a year ago

Strictly speaking range is a python built in function. You can do it with for i in str1 and swap out the value of i withr2 when n == 0

Pankaj Singhal Over a year ago

@RolfofSaxony Edited.

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