How to accumulate within a loop python

Question

I am new to programming and I am having difficulty accumulating within a loop

    wrong_guesses=0
    formSoFar=''
    game_over=False
    while (game_over==False and wrong_guesses<max_guesses):
        guess1= raw_input("Please enter an operation symbol or digit: ")
        if (guess1 in formula):
            print "Your guess is correct!"
            for i in range (len(formula)):
                if (randomFormula[i] == guess1):
                    formSoFar += formula[i]
                else:
                    formSoFar+= "-"
            print "The formula you have guessed so far is: ",formSoFar

Supposed the equation the user is trying to guess is 1+2+3 and their first guess is 2 the formSoFar is --2-- but the second time they guess it should show the first guess as well so if they guess 1 it should be 1-2-- but this code is printing--2--1-2-- please help :(

Answer 1

In each loop, you are appending characters to formSoFar. What you want to do instead is have it start with some value and edit it as you go:

formSoFar = ['-'] * len(formula)

while not game_over and wrong_guesses < max_guesses:
    guess = raw_input(...)
    if guess in formula:
        for i, c in enumerate(formula):
            if c == guess:
                formSoFar[i] = c

        print 'The formula you have guessed so far is:', ''.join(formSoFar)

Also note that you don't need ()s in an if statement. That's a C/C++/Java thing.