discord.py get user input (simplified)
import ctx #You might need to install this seperately from discord.py (if you don't have it)
# lets say you want to change the bot's prefix...
async def prefix(ctx):
await ctx.send(f'What do you want to set the prefix to?')
# wait for responce and lower the text for easy use
value = await client.wait_for('message')
value = value.content.lower()
# this is where you would change the prefix value in a config file or something
# example: parser.set('prefix', value) <--- the value is your looking for
# prints and messages the output (you don't really need this)
print(ctx.message.author, 'Changed the prefix to:', value)
await ctx.send('Prefix changed to: {}'.format(value))