str comparaison problem

async def check_for_new_post(bot):
    global subscriptions

    # TODO: Fetch data from file
    # subscriptions = get_file()
    # if subscriptions != 'None':

    await bot.wait_until_ready()
    while not bot.is_closed:
        for subscription in subscriptions:
            sub = read_it_on_reddit.sub_exists(subscription.subreddit)
            new_posts = read_it_on_reddit.get_newest_post(subscription.subreddit)

            for new_post in new_posts:
                if subscription.old_post != new_post.fullname:
                    subscription = subscription._replace(old_post=new_post.fullname)
                    print("old: " + subscription.old_post, type(subscription.old_post), " New: ", new_post.fullname,
                          type(new_post.fullname))
                    await bot.send_message(subscription.channel,
                                           embed=read_it_on_reddit.create_embed("New post from:", new_post, sub))
        await asyncio.sleep(5)