Code

import telegram
from telegram import ReplyKeyboardMarkup
from telegram.ext import (
    Updater,
    CommandHandler,
    MessageHandler,
    Filters,
)
import requests
import os
import sys

# request token from bot in environment variables
TOKEN = os.getenv('TELEGRAM_TOKEN')
mode = os.getenv('MODE')

# local access (developing)
if mode == 'dev':
    def run(updater):
        updater.start_polling()
        updater.idle()

# access to heroku (production)
elif mode == 'prod':
    def run(updater):
        PORT = int(os.environ.get('PORT', '8443'))
        HEROKU_APP_NAME = os.environ.get('HEROKU_APP_NAME')
        updater.start_webhook(listen='0.0.0.0', port=PORT, url_path=TOKEN)
        updater.bot.set_webhook(f"https://{HEROKU_APP_NAME}.herokuapp.com/{TOKEN}")
else:
    print('without MODE')
    sys.exit()

# bot start function
def start(update, context):
    keyboard = [['USD', 'AED', 'AFN', 'ALL', 'AMD'],
                ['ANG', 'AOA', 'ARS', 'AUD', 'AWG'],
                ['AZN', 'BAM', 'BBD', 'BDT', 'BGN'],
                ['BHD', 'BIF', 'BMD', 'BND', 'BOB'],
                ['BRL', 'BSD', 'BTN', 'BWP', 'BYN'],
                ['BZD', 'CAD', 'CDF', 'CHF', 'CLP'],
                ['CNY', 'COP', 'CRC', 'CUC', 'CUP'],
                ['CVE', 'CZK', 'DJF', 'DKK', 'DOP'],
                ['DZD', 'EGP', 'ERN', 'ETB', 'EUR'],
                ['FJD', 'FKP', 'FOK', 'GBP', 'GEL'],
                ['GGP', 'GHS', 'GIP', 'GMD', 'GNF'],
                ['GTQ', 'GYD', 'HKD', 'HNL', 'HRK'],
                ['HTG', 'HUF', 'IDR', 'ILS', 'IMP'],
                ['INR', 'IQD', 'IRR', 'ISK', 'JMD'],
                ['JOD', 'JPY', 'KES', 'KGS', 'KHR'],
                ['KID', 'KMF', 'KRW', 'KWD', 'KYD'],
                ['KZT', 'LAK', 'LBP', 'LKR', 'LRD'],
                ['LSL', 'LYD', 'MAD', 'MDL', 'MGA'],
                ['MKD', 'MMK', 'MNT', 'MOP', 'MRU'],
                ['MUR', 'MVR', 'MWK', 'MXN', 'MYR'],
                ['MZN', 'NAD', 'NGN', 'NIO', 'NOK'],
                ['NPR', 'NZD', 'OMR', 'PAB', 'PEN'],
                ['PGK', 'PHP', 'PKR', 'PLN', 'PYG'],
                ['QAR', 'RON', 'RSD', 'RUB', 'RWF'],
                ['SAR', 'SBD', 'SCR', 'SDG', 'SEK'],
                ['SGD', 'SHP', 'SLL', 'SOS', 'SRD'],
                ['SSP', 'STN', 'SYP', 'SZL', 'THB'],
                ['TJS', 'TMT', 'TND', 'TOP', 'TRY'],
                ['TTD', 'TVD', 'TWD', 'TZS', 'UAH'],
                ['UGX', 'UYU', 'UZS', 'VES', 'VND'],
                ['VUV', 'WST', 'XAF', 'XCD', 'XDR'],
                ['XOF', 'XPF', 'YER', 'ZAR', 'ZMW']]

    markup = ReplyKeyboardMarkup(keyboard, one_time_keyboard=True)

    update.message.reply_text(
        text='''
        Hello! 👋🏻
        
What can this bot do?

1️⃣-Select from the keyboard the currency you want to know the exchange value against other currencies.
 
2️⃣-You can also just type the currency 
indicator.

3️⃣-Use the /exchange command followed by  the currency indicator.
 
4️⃣-Use /exchange_value followed by 
the two currencies you want to know 
their conversion rate.
        ''',
        reply_markup=markup
    )

# one-to-many exchange function
def exchange(update, context):
    try:
        moneda = context.args[0]
    except Exception as e:
        print(type(e).__name__)
        context.bot.send_message(
            chat_id=update.effective_chat.id,
            text="""
                Please you don't use the command correctly,
                you have to send followed by the command the
                currency of which you want to know the
                conversion rate.
                Example:
                /exchange usd 
                """
            )
    else:
        r = requests.get(f"https://v6.exchangerate-api.com/v6/YourKey/latest/{moneda}")

        if r:
            r_json = r.json()
            text = ""

            for key, value in r_json['conversion_rates'].items():
                rate = f"{key} : {value}\n"
                text += rate

            update.message.reply_text(
                text=text
            )
        else:
            update.message.reply_text(
                text="I don't recognize that currency, please send correctly the identifier of the currency in question."
            )

# one-to-one exchange function
def exchange_value(update, context):
    try:
        currency = context.args[0].upper()
        target_currency = context.args[1].upper()
    except telegram.TelegramError as e:
        print(e.message)
        context.bot.send_message(
            chat_id=update.effective_chat.id,
            text="""
                Please you don't use the command correctly,
                you have to send followed by the command the
                2 currencies of which you want to know the
                conversion rate.
                Example:
                /exchange_value usd eur
                > x USD = y EUR
                """
            )
    else:
        r = requests.get(f"https://v6.exchangerate-api.com/v6/YourKey/latest/{currency}")

        if r:
            r_json = r.json()
            try:
                rate = r_json['conversion_rates'][target_currency]
            except Exception as e:
                print(type(e).__name__)
                update.message.reply_text(
                    text="I don't recognize that currency, please send correctly the identifier of the currency in question."
                )
            else:
                update.message.reply_text(
                    text=f"1 {currency} = {rate} {target_currency}"
                )
        else:
            update.message.reply_text(
                text="I don't recognize that currency, please send correctly the identifier of the currency in question."
            )

# one-to-many exchange function for message
def exchange_message(update, context):
    currency = update.message.text
    r = requests.get(f"https://v6.exchangerate-api.com/v6/YourKey/latest/{currency}")

    if r:
        r_json = r.json()
        text = ""

        for key, value in r_json['conversion_rates'].items():
            rate = f"{key} : {value}\n"
            text += rate

        update.message.reply_text(
            text=text
        )
    else:
        update.message.reply_text(
            text="I don't recognize that currency, please send correctly the identifier of the currency in question."
        )


def error_handler(update, context):
    """
    You can define here what to do with the errors raised by the bot.
    In this case, we only print those errors to the logs.
    """
    try:
        raise context.error
    except telegram.TelegramError as e:
        print(e.message)


if __name__ == "__main__":
    updater = Updater(token=TOKEN, use_context=True, workers=30)
    # dispatcher configuration
    dp = updater.dispatcher
    dp.add_error_handler(error_handler)

    command_handlers = {
        'start': start,
        'exchange': exchange,
        'exchange_value': exchange_value
    }

    message_handlers = [
        (Filters.text, exchange_message)
    ]

    # Init command handlers
    for key, value in command_handlers.items():
        dp.add_handler(CommandHandler(key, value, run_async=True))

    # Init filters
    for filter, callback in message_handlers:
        dp.add_handler(MessageHandler(filter, callback, run_async=True))

    # starting the bot
    run(updater)

Examples in Telegram