How to translate enumerate() to a for loop in Python

I have the following code which finds the index of a guessed number from a long number, however I cannot use enumerate. What would the equivalent for loop look like for this:

guess = input()
long_number = ('5666')
a = [i for i, number in enumerate(long_number) if number == guess]
print(a)

e.g. Output: if guess = 5, then the output should be [0].

How would you do this using while, for and/or if functions only?