why this code didn't break?

Question

string = "abc"
print(string[-1])
while True:
position = string.find("c")
if position == -1:
break
string = string[:position] + "f" + string[position+len("c"):]

print(string)

c in string is the latest one the position is -1, so i think it should go break.

Answer 1

-1 works for list indices, not characters in strings (at least not in this case). -1 will be returned on failure (character not found), not if the character you're looking for is the last character of the string. You should use something like "if position == len(string)-1" or "if string.endswith('c')" instead. And never use "string", "list" etc. as a name for a string, list etc. It's not necessarily wrong, but bad style and can possibly break your code.