Replace nth occurrence of substring in string

Question

I want to replace the n\'th occurrence of a substring in a string.

There\'s got to be something equivalent to what I WANT to do which is

mystring.repl

Answer 1

Elegant and short:

def replace_ocurrance(string,from,to,num)
     strange_char = “$&$@$$&”
     return string.replace(from,strange_char,num).replace(strange_char, from,num-1).replace(to, strange_char,1)