Why doesn't isalpha() work for sanitizing user input? - python-3.x

Question

The trouble I'm having here is that the isalpha() function isn't doing what it's supposed to do, users are able to send messages that contain characters that are not alphabetical. I'm not sure why this occurs. I assumed that it was some kind of hosting issue (which from the looks of it wasn't) prior to assuming that there was a logical error in my code, but logically it makes sense to me which perhaps is wrong? I kinda also made the assumption that it had to do with the function not being asynchronous, I don't know I probably am reaching with that one.
import discord
from discord.ext import commands
import re
class Shiritori(commands.Cog):
""" Start a new word from the last letter of the one before. """
def __init__(self, client):
self.client = client
self.repeats = re.compile(r'(.)\1{2,}') # Matches spam like 'eeeeeee'
self.shiritori_channel = 578788555120312330 # Official
#commands.Cog.listener()
async def on_message(self, message):
try:
if message.channel.id == self.shiritori_channel:
previous_message = (await message.channel.history(limit=2).flatten())[1].content
repeats_mo = self.repeats.search(message.content)
if not repeats_mo and message.content.isalpha():
if previous_message[-1].lower() != message.content[0].lower():
await message.author.send(
f'Your message must start with the last letter of the latest message!')
await message.delete()
else:
await message.author.send("You can't do that here!")
await message.delete()
except discord.Forbidden:
await message.delete()

Answer 1

I guess you are expecting that any non-ascii English character is not alpha.
But
According to the doc,
str.isalpha() Return True if all characters in the string are
alphabetic and there is at least one character, False otherwise.
Alphabetic characters are those characters defined in the Unicode
character database as “Letter”, i.e., those with general category
property being one of “Lm”, “Lt”, “Lu”, “Ll”, or “Lo”. Note that this
is different from the “Alphabetic” property defined in the Unicode
Standard.
So for example à (french a) or любовь are also considered alpha
'à'.isalpha()
True
'любовь'.isalpha()
True
If you want the english letters, use isascii():
'à'.isascii()
False