tele

import sys
from getpass import getpass
from time import sleep

try:
    from telethon import TelegramClient
except ImportError as e:
    print("telethon is not available in your system. Installing ...")
    import pip
    pip.main(['install', "telethon", "--user"])
    input("Please restart the script to apply new package")
    exit()

from telethon import TelegramClient
from telethon.errors import SessionPasswordNeededError
# from telethon.errors.rpc_error_list import UsernameNotOccupiedError
from telethon.errors.rpcbaseerrors import FloodError
# from telethon.errors.rpcbaseerrors import ChatAdminRequiredError
from telethon.tl.functions.channels import GetParticipantsRequest
from telethon.tl.functions.contacts import ResolveUsernameRequest
from telethon.tl.types import ChannelParticipantsSearch, InputChannel

# First you need create app on https://my.telegram.org
api_id = 518161
api_hash = 'b5ef3577c856cb8c22d3f5d4eab75537'
phone = '+84389908656'
limit = 100

def dump_users(chat_info, client):
    counter = 0
    offset = 0
    chat_object = InputChannel(chat_info['chat_id'], chat_info['access_hash'])
    all_participants = []
    print('Process...')
    while True:
        try:
            participants = client.invoke(
                            GetParticipantsRequest( chat_object,
                                                    ChannelParticipantsSearch(''),
                                                    offset,
                                                    limit,
                                                    hash=0
                                                    )
                            )
            if not participants.users:
                break
            all_participants.extend(['{}, {}'.format(x.id, x.username)
                               for x in participants.users])
            users_count = len(participants.users)
            offset += users_count
            counter += users_count
            print('{} users collected'.format(counter))
        except e:
            print(e)
            break
        sleep(2)
        with open('users.txt', 'w') as file:
            file.write('\n'.join(map(str, all_participants)))


def main():
    channel_name = input('Input a channel name, without "@": ')
    client = TelegramClient('current-session', api_id, api_hash)
    print('Connecting...')
    client.connect()
    if not client.is_user_authorized():
        try:
            client.send_code_request(phone)
            print('Sending a code...')
            client.sign_in(phone, code=input('Enter code: '))
            print('Authorized Successfully!')
        except FloodError as FloodError:
            print('Flood wait: {}.'.format(FloodError))
            sys.exit()
        except SessionPasswordNeededError:
            client.sign_in(password=getpass('Enter password: '))
            print('Authorized Successfully!')

    try:
        chat = client(ResolveUsernameRequest(channel_name))
    except e:
        print('Chat/channel not found!')
        sys.exit()
    chat_info = {
        'chat_id': chat.peer.channel_id,
        'access_hash': chat.chats[0].access_hash
    }

    dump_users(chat_info, client)
    print('Done!')

if __name__ == '__main__':
    main()