Storing bot, user and chat related data

Sometimes you need to temporarily store some information about the current user and/or chat for later use. An example of this would be a survey bot that asks the user a series of questions one after another and saves them to your database when all answers are collected.

bot_data, user_data and chat_data

The telegram.ext framework provides a built-in solution for this common task. To understand how it works, let's take a look at a naïve solution using a global variable. In case you're in a hurry, you can also jump straight to the explanation.

Bad Example

The following complete example bot provides a very simple key/value storage. When you use the /put command to store a value, it returns an ID which you can use with the /get command to retrieve the stored value.

It uses a global dictionary named all_user_data that maps a user ID to a dict that represents the user specific storage.

from uuid import uuid4
from telegram.ext import Updater, CommandHandler

all_user_data = dict()

def put(update, context):
    """Usage: /put value"""
    # Generate ID and seperate value from command
    key = str(uuid4())
    value = update.message.text.partition(' ')[2]

    user_id = update.message.from_user.id

    # Create user dict if it doesn't exist
    if user_id not in all_user_data:
        all_user_data[user_id] = dict()

    # Store value
    user_data = all_user_data[user_id]
    user_data[key] = value

    update.message.reply_text(key)

def get(update, context):
    """Usage: /get uuid"""
    # Seperate ID from command
    key = update.message.text.partition(' ')[2]

    user_id = update.message.from_user.id

    # Load value
    try:
        user_data = all_user_data[user_id]
        value = user_data[key]
        update.message.reply_text(value)

    except KeyError:
        update.message.reply_text('Not found')

if __name__ == '__main__':
    updater = Updater('TOKEN', use_context=True)
    dp = updater.dispatcher

    dp.add_handler(CommandHandler('put', put))
    dp.add_handler(CommandHandler('get', get))

    updater.start_polling()
    updater.idle()

If you read the code carefully, you might have noticed that the code that gets the current user_data from all_user_data is repeated in both callbacks.

Good Example

from uuid import uuid4
from telegram.ext import Updater, CommandHandler

def put(update, context):
    """Usage: /put value"""
    # Generate ID and seperate value from command
    key = str(uuid4())
    value = update.message.text.partition(' ')[2]

    # Store value
    context.user_data[key] = value

    update.message.reply_text(key)

def get(update, context):
    """Usage: /get uuid"""
    # Seperate ID from command
    key = update.message.text.partition(' ')[2]

    # Load value
    try:
        value = context.user_data[key]
        update.message.reply_text(value)

    except KeyError:
        update.message.reply_text('Not found')

if __name__ == '__main__':
    updater = Updater('TOKEN', use_context=True)
    dp = updater.dispatcher

    dp.add_handler(CommandHandler('put', put))
    dp.add_handler(CommandHandler('get', get))

    updater.start_polling()
    updater.idle()

Note the following differences:

• The global variable all_user_data was removed
• The repeated code to get the storage of the current user was removed
• The code to ensure that the storage exists was removed
• Both the put and get functions use context.user_data

Explanation

By using context.user_data in any Handler callback, you have access to a user-specific dict.

Every time the bot receives a message, the handler for that message finds (or creates) the user_data of the user who sent the message. This dictionary is shared across all handlers of the bot.

What about bot_data and chat_data?

chat_data works in the exact same way as user_data, except it is managed per chat instead of every user. Use context.chat_data to get access to this dict. As of version 12.4 bot_data is provided as well and works in the exact same way as user_data, except it's a single dictionary for your bot. Use context.bot_data to get access to this dict.

Notes & Tips

• Everything is stored in memory. This means that all bot_data, user_data and chat_data is deleted when the bot process ends. If you don't want this, have a look at the persistent page.
• Empty bot_data, user_data and chat_data dictionaries are automatically deleted from memory after the update is processed.
• If not empty, bot_data, user_dataandchat_data` will be kept until the process ends.
• user_data and chat_data are different dictionaries even for private chats.
• You can not assign a new value to bot_data, user_data or chat_data. Instead of user_data = {} and user_data = other_dict, use user_data.clear() and/or user_data.update(other_dict) respectively.

Chat Migration

If a group chat migrates to supergroup, its chat id will change. Since the chat_data dicts are stored per chat id you'll need to transfer the data to the new id. Here are the two situations you may encounter:

Status Updates sent by Telegram

When a group migrates, Telegram will send an update that just states the new info. In order to catch those, simply define a corresponding handler:

def chat_migration(update, context):
    m = update.message
    dp = context.dispatcher # available since version 12.4

    # Get old and new chat ids
    old_id = m.migrate_from_chat_id or m.chat_id
    new_id = m.migrate_to_chat_id or m.chat_id

    # transfer data, if old data is still present
    if old_id in dp.chat_data:
        dp.chat_data[new_id].update(dp.chat_data.get(old_id))
        del dp.chat_data[old_id]

...

def main():
    updater = Updater("TOKEN", use_context=True)
    dp = updater.dispatcher # available since version 12.4

    dp.add_handler(MessageHandler(Filters.status_update.migrate, chat_migration))

...

To be entirely sure that the update will be processed by this handler, either add it first or put it in its own group.

ChatMigrated Errors

If you try e.g. sending a message to the old chat id, Telegram will respond by a Bad Request including the new chat id. You can access it using an error handler:

def error(update, context):
    """Log Errors caused by Updates."""
    logger.warning('Update "%s" caused error "%s"', update, context.error)

    if isinstance(context.error, ChatMigrated):
        new_chat_id = context.error.new_chat_id

Unfortunately, Telegram does not pass along the old chat id, so there is currently no simple way to perform a data transfer like above within the error handler. So make sure, that you catch the status updates! Still, you can wrap your requests into a try-except-clause:

def my_callback(update, context):
    dp = context.dispatcher # available since version 12.4

    ...

    try:
        context.bot.send_message(chat_id, text)
    except ChatMigrated as e:
        new_id = e.new_chat_id

        # Resend to new chat id
        context.bot.send_message(new_id, text)

        # Transfer data
        if chat_id in dp.chat_data:
            dp.chat_data[new_id].update(dp.chat_data.get(chat_id))
            del dp.chat_data[chat_id]

    ...