python-telegram-bot dialog interrupt workaround / converstaionhandler

telegram_bot_dialog_interrupt.py

""" 
    workaround for dialog interruption for python-telegram-bot 
    see the problem of parallel dialogs:
    https://stackoverflow.com/questions/64146229/python-telegram-bot-disallow-nested-conversations
    https://github.com/python-telegram-bot/python-telegram-bot/issues/1640
"""

from telegram import ReplyKeyboardMarkup
from telegram.ext import (
    Updater,
    CommandHandler,
    MessageHandler,
    Filters,
    ConversationHandler,
)

(
    A1, A2, 
    B1, B2
) = range(4)

def cancel(update, context):
    update.message.reply_text('cancel dialog')
    return ConversationHandler.END

def start(update, context):
    reply_keyboard = [['A', 'B']]
    markup_key = ReplyKeyboardMarkup(reply_keyboard, one_time_keyboard=True)
    update.message.reply_text('select dialog', reply_markup=markup_key,)
    return None

def enter_a(update, context):
    update.message.reply_text('a1')
    return A1
    
def a1(update, context):
    update.message.reply_text('a2')
    return A2

def a2(update, context):
    update.message.reply_text('exit a')
    context.user_data['in_conversation'] = False
    return ConversationHandler.END

def enter_b(update, context):
    update.message.reply_text('b1')
    return B1
    
def b1(update, context):
    update.message.reply_text('b2')
    return B2

def b2(update, context):
    update.message.reply_text('exit b')
    return ConversationHandler.END


if __name__ == '__main__':
    # specify your bot token here
    updater = Updater("1586839780:AAEte-6_VVVGbqh7c7wmrcxkUZX0R2TRiJc")

    # dispatcher to attach handlers
    dispatcher = updater.dispatcher

    # dialog A: press 'a' multiple time to go through the dialog
    dispatcher.add_handler(ConversationHandler(
        entry_points=[MessageHandler(Filters.regex('^[aA]$'), enter_a)],
        states= {
            A1: [MessageHandler(Filters.regex('^[aA]$'), a1)],
            A2: [MessageHandler(Filters.regex('^[aA]$'), a2)]
        },
        fallbacks=[MessageHandler(Filters.regex('^[bB]$'), cancel)] # NOTE: pressing 'b' cancels current dialog and starts dialog 'B'
    ), 1) # NOTE: add handler to group 1

    # dialog B: press 'b' multiple time to go through the dialog
    dispatcher.add_handler(ConversationHandler(
        entry_points=[MessageHandler(Filters.regex('^[bB]$'), enter_b)],
        states= {
            B1: [MessageHandler(Filters.regex('^[bB]$'), b1)],
            B2: [MessageHandler(Filters.regex('^[bB]$'), b2)]
        },
        fallbacks=[MessageHandler(Filters.regex('^[aA]$'), cancel)] # NOTE: pressing 'a' cancels current dialog and starts dialog 'A'
    ), 2) # NOTE: add handler to group 2

    # shows main menu
    dispatcher.add_handler(CommandHandler('start', start), 3)

    # start bot
    updater.start_polling()
    updater.idle()