Python While Loop - Variable Not Updating?

This code simply looks for a string in another string and returns the last postion of the occurance in the search string or -1 if its is not found. I don't understand why my vari

Solution 1:

You don't change the value of next_y in the while loop, so its value isn't updated. Value of next_y is calculated once and compared for ever (or only once). To update this value you should call 'next_y = x.find(y, pos + 1)' in the loop.

def find_last(x,y):
  if x.find(y) == -1:
    return -1pos = x.find(y)
  next_y = x.find(y, pos + 1)
  while next_y != -1:
    pos = pos + next_y
    next_y = x.find(y, pos + 1)
  returnpos

search = 'tom ran up but tom fell down'
target = 'tom'print(find_last(search,target))

Solution 2:

As mentioned in the comments, if you want to update next_y, you need to do it explicitly:

while next_y != -1:
    pos = pos + next_y
    next_y = x.find(y, pos + 1)