def registo(numaluno, password):
    found = False
    with open("Accounts.txt", "r+") as file:
        for line in file:
            user, pw = line.split(":")
            if numaluno == user:
                print("O utilizador",numaluno,"já existe")
                found = True
    file.close()
    if found == True:
        mudarpw = input("Pretende alterar a password? [S/N]: ")
        if mudarpw == "s" or mudarpw == "S":
            output = ""
            while True:
                password = input("Insira a nova password: ")
                if validarPW(password):
                    for line in fileinput.input(["Accounts.txt"], inplace=True):
                        if line.strip().startswith(numaluno):
                            line = numaluno+":"+password+"\n"
                        output = output + line
                    f = open("Accounts.txt", "w")
                    f.write(output)
                    f.close()
                    print ("Alterada com sucesso")
                    break

    if not found:
        with open("Accounts.txt", "a+") as file:
            account = '\n%s:%s'%(numaluno,password)
            file.write(account)
            print ('O utilizador foi guardado com sucesso')