Question

I have the following code:

letters = 'abcdefg'    
for i in letters:
        if ...
        #condition that tests something I need
        #once condition is satisfied, something is done, the condition is modified
        # and letters becomes:
                letters = letters.replace(i,'')
                ### Now I want to start this for loop again because my condition
                ### may now be met with the initial letters

How do I get my loop to start from the beginning again?

Answer 1

You could try an approach along these lines (tweak as needed to fit your code):

i = 0
while i < len(letters):
    if ....

       letters = letters.replace(letters[i], '')  # probably what you want
       i = 0
    else:
       i += 1

The iteration in your loop is controlled by the value of i. As long as i is less than the length of your string (7) it will keep looping, each time incrementing the value of i (which serves as a counter) in the loop. When you set i = 0 you are (re)starting the counter again.

Note that unlike with the for-loop where you had for i in letters (and i successively got the value of a letter), i is a simple counter, so to access a given letter you have to index into it. I.e., letters[i]