Telegram bot made with Telethon that sends a message to all members of a specified group

telegram-bot.py

from telethon.sync import TelegramClient
import asyncio
from os import path

# Logging configuration


def login(phone, api_id, api_hash):
    global client
    client = TelegramClient(phone, int(api_id), api_hash)
    client.connect()
    if not client.is_user_authorized():  # If further authentication is needed via text
        client.send_code_request(phone)
        print('Further authentication required in order to log in, a code has been sent to the phone number.')
        client.sign_in(phone, input('Enter the code: '))
    print(f"Logged in as {client.get_me().username}!")


async def get_users(group):
    user_list = await client.get_participants(group)
    users = [user.username for user in user_list if user.username is not None]
    with open(input('Output file: '), 'w+') as f:
        for user in users:
            f.write(user+"\n")
        print(f"{len(user_list)} users exported to {f.name}!")


async def send_messages(message, users):
    for user in users:
        await client.send_message(user, message)
        print(f"Message sent to {user}.")


def save_credentials(*args):
    print('Saving credentials...')
    with open('creds.txt', 'w+') as f:
        for arg in args:
            f.write(f'{arg}\n')


def read_credentials():
    print('Reading credentials...')
    with open('creds.txt', 'r') as f:
        return [line for line in f.read().split('\n') if line is not '']


def load_users():
    with open('users.txt', 'r') as f:
        return f.read().split('\n')


def main():
    # Check if credentials are saved, otherwise get them from the user
    if path.exists('creds.txt'):
        credentials = read_credentials()
        login(*credentials)
    else:
        # Needed for login authentication
        print('Find these at https://my.telegram.org/ under API Development tools.')
        save_credentials(
            input('Phone # (EX: +11234560000): '),
            input('api_id (EX: 101340): '),
            input('api_hash (EX: ca123req3410fdls343207cc743): ')
        )
        credentials = read_credentials()
        login(*credentials)
    # Async routines
    loop = asyncio.get_event_loop()
    loop.run_until_complete(get_users(input('Group name: ')))
    loop.run_until_complete(send_messages(input('Message: '), load_users()))


if __name__ == '__main__':
    main()