Local message thingy

import ast
s_r = ''
Log_Reg = ''
print("Messages storer")
new_dict = {}
recipient = ''
file_name = 'user_data.txt'
test = 0
username = ''
password = ''
user_index = ''
msgtoprint = ''
start_count = 0

def encode_user_cred(input):
    list_ = list(input.items())
    return str(list_)

def decode_user_cred(input):
    test = 0
    input = str(input)
    input = (input.replace('(', '').replace('[', '').replace(')','').replace(']', '').replace("'", '').replace(' ', '')) + ','
    global new_dict
    global list_2
    list_1 = []
    list_2 = []
    text = ''
    text_ = ''
    for i in input:
        if i != ',':
            text += i
        else:
            list_1.append(text)
            text = ''
            test += 1
            if test % 2 == 0 :
                list_2 += [list_1]
                list_1 = []
                text = ''
    new_dict = dict(list_2)
def encode_char(input):
    global encoded_characters
    global characters
    send = ''
    if input != None:
        for i in input:
            send+= encoded_characters[characters.index(i)]
    return send
def decode_char(input):
    global encoded_characters
    global characters
    send = ''
    if input != None:
        for i in input:
            send+= characters[encoded_characters.index(i)]
    return send
def encrypt(input):
    return encode_char(encode_user_cred(input))
def decrypt(input):
    return decode_user_cred(decode_char(input))

def save(input_value, filename):
    global file_name
    with open(filename, 'a') as f:
        f.write(str(input_value) + 'N')
def load_value(filename):
    global file_name
    with open(filename , 'r') as f:
        read = f.read()
    return read
def create(filename):
    global file_name
    with open(filename , 'a') as f:
        pass
try:
    create('user_data.txt')
    create('messages.txt')
    decode_user_cred(load_value(file_name))

except:
    pass


def get_index(username):
    global list_2
    index = 0
    for i in list_2:
        if username == i[0]:
            return index
        index += 1
def get_username(index):
    index = int(index)
    global list_2
    count = 0
    for i in list_2:
        if index == get_index(i[0]):
            return i[0]
    count += 1
def save_password():
    global password
    password = ''
    password = input("Enter a password: ")
    while ',' in password or '[' in password or ']' in password or '(' in password or ')' in password or ' ' in password or password == '':
        if(password == ''):
            pass
        else:
            print("password cannot contain spaces or special characters: , [ ] ( )")
            password = input("Enter a password: ")
    re_enter_password = input("Repeat password: ")
    if re_enter_password != password:
        print("Password mismatch")
        re_enter_password = input("Repeat password: ")
        if re_enter_password != password:
            save_password()
def passwords():
    global password
    password = input("What is the passowrd?: ")
    if password == cloud_user_credentials.get(username):
        print("Login Success!")
        return 1
    else: return 0
def start(mode):
    global password
    global username
    global cloud_user_credentials
    global test
    global Log_Reg
    global start_count
    re_enter_password = ''
    if mode == 0: Log_Reg = input("Log in or Sign up?: ")
    if mode == 3 :Log_Reg = "SIGN UP"
    if Log_Reg.upper() == "LOG IN":
        username = input("What is your username? (CASE SENSITIVE): ")
        if cloud_user_credentials.get(username) != None:
            password = input("What is the passowrd?: ")
            if password == cloud_user_credentials.get(username):
                print("Login Success!")
            else:
                for i in range(3,0,-1):
                    print("Wrong password, " + "you have " + str(i)+" tries remaining!")
                    test = passwords()
                    if test == 1:
                        break
                    if i == 1:
                        start(0)
        else:
            print("Username does not exist!")
            start_count += 1
            if start_count == 2:
                dec =input('Would you like to sign up? yes/no: ')
                if dec.upper() == ('YES'):
                    start(3)
                elif dec.upper() == 'NO': start_count = 0
                else:
                    dec =input('Would you like to sign up? yes/no: ')
            else:
                start(1)
    elif Log_Reg.upper() == "SIGN UP":
        username = input("Choose your username: ")
        while ',' in username or '[' in username or ']' in username or '(' in username or ')' in username or ' ' in username or username == '':
            if(username == ''):
                    pass
            else:
                print("Username cannot contain spaces or special characters: , [ ] ( )")
            username = input("Choose your username: ")
        if cloud_user_credentials.get(username) == None:
            save_password()
            local_user_credentials.update({username:password})
            save(encrypt(local_user_credentials), file_name)
            print("Sign Up Success!")
            decode_user_cred(load_value(file_name))
            cloud_user_credentials = new_dict
        else:
            print("Username taken")
            start(1)
    else: print("wrong input!"), start(0)

def send_recieve():
    global user_index, cloud_user_credentials, new_dict
    file_name = 'user_data.txt'
    user_index = str(get_index(username))
    s_r = input("Would you like to send or recieve a message?: ")
    if s_r.upper() == 'SEND':
        file_name = 'user_data.txt'
        decrypt(load_value(file_name))
        cloud_user_credentials = new_dict
        sender = username
        recipient = ''
        while cloud_user_credentials.get(recipient) == None or recipient == sender:
            recipient = input(username + ", who would you like to send to?: ")
            if cloud_user_credentials.get(recipient) == None:
                print("""'""" + recipient + """'"""+ " is not an existing user")
            elif sender == recipient:
                print("You cannot send to yourself!")
        recipient_index = str(get_index(recipient))
        message = input("What would you like to send to " +recipient + "?: ")
        local_message.update({recipient_index: user_index + ':' + message})
        file_name = 'messages.txt'
        save(encrypt(local_message), file_name)
        print(local_message)
        print(username)

        print("Done!")
    elif s_r.upper() == 'RECIEVE':
        file_name = 'messages.txt'
        decrypt(load_value(file_name))
        cloud_message = new_dict
        if cloud_message.get(str(user_index)) != None:
            recived_message = cloud_message.get(str(user_index))
            msgtoprint = ''
            count = ''
            decrypt(load_value('user_data.txt'))
            for i in recived_message:

                if i != ':':
                    count += i
                else:
                    if (count != '0'):  print(count) ,'From: ' + str(msgtoprint = get_username(count))
                    else: msgtoprint = 'From: ' + str(get_username(0))
                    print(msgtoprint) #prints message sender
                    break
                msgtoprint = ''
                for i in (str(recived_message).replace((count + ':') , '')):
                    msgtoprint += i
            print(str(recived_message).replace((count + ':') , '')) # prints recieved message

        else:
            print("You have no messages")
    else: send_recieve()

import string
i_ = 0
characters = list("""~[`! #$%^&*()-_=+]'"|:<>/?.""") + list("{") + list("}")+list(",") + list('0123456789')
letters = list(string.ascii_lowercase) + list(string.ascii_uppercase)
characters += letters
encoded_letters = list('gkynufcrbeljzavwdthxspimoq') + list('gkynufcrbeljzavwdthxspimoq'.upper())
encoded_characters = list('7963841250') + list(""" )?$=:+&{"[|%-!'*>.~`_]^#<(/}""") + list(",")
encoded_characters = encoded_letters + encoded_characters
decrypt(load_value(file_name))
local_message = {}
recived_message = ''
cloud_message = {}
cloud_user_credentials = new_dict
local_user_credentials = {}
list_user_credentials = list_2
user_data = []

start(0)
send_recieve()