Breaks down a string an iterates its characters.

charFinder.py

def detectSpecificChars():
	key = "masterkey"

	string = raw_input ("Insirt a string: ")
	if string == key:
		return None

	letterArray = []
	positionArray = []

	for letter in string:
		letterArray = letterArray + [letter]

	for i in range(len(letterArray) - 1):
		if letterArray[i] == "a":
			positionArray = positionArray + [i]
			

	''' 
	A mesma coisa que o loop anterior, mas itera os valores em vez dos indices.

	for element in letterArray:
		if element == "a":
			return "Contem uma letra 'A'" '''

	return "Letra 'A' na posicao: \n" + str(positionArray)


while True:
	displayString = detectSpecificChars() 
	if displayString != "" and displayString != None:
		print(displayString)
	else:
		break;