Confused on a for loop for a hangman game?

Question

The hangman code that I am referencing comes from the Invent Your Own Games with Python book:

In the function that displays the game board, there is a for loop that replaces a string composed of underscores with the correct, guessed letters corresponding to whatever the secretWord is:

    for i in range(len(secretWord)):
        if secretWord[i] in correctLetters:
            blanks = blanks[:i] + secretWord[i] + blanks[i+1]

I have trouble trying to understand and visualize the line blanks = blanks[:i] + secretWord[i] + blanks[i+1] Let's say secretWord = "otter" and blanks = "_____" (five underscores). How exactly would the for loop work?

Answer 1

Let's imagine you got the letter 't' correct. So correctLetters=['t'] and we go through our secret word, to see where the t appears.

For i = 0 nothing happens, 'o' is not in our correctLetters.
For i = 1 we got the 't', it's part of correctLetters, so we are able to do the magic with the blanks:

| blanks[:i] gets the String until position i=1, so here: '_'
secretWord[i] gives you the 't', as i=1
blanks[i+1] gives you all the rest of the string, starting from position i+1=2 -> ___

Overall you have _t___ after this iteration.

You'll we do the same again with another t (i=2 now) and you'll have: blanks = _tt__

And then it's super easy to guess Otter, right ;)