Discord.py: Waiting for one on_raw_reaction_add to finish before completing another - discord

Question

I am creating a movie bot on discord that selects 10 random movies, members vote on it, and the winning movie (random in case of tie) gets a discussion thread created. All of this is done through scheduled functions.
I recently switched from doing ✅ on every movie summary, to a poll message with keypad numbers 1️⃣,2️⃣,3️⃣,4️⃣,5️⃣,6️⃣,7️⃣,8️⃣,9️⃣,🔟. Users react with the number to the corresponding movie. Voting works, but I am trying to make it so users can only vote on one movie for each poll.
This is done via on_raw_reaction_add, the issue is, if a user spams reactions, the logic has potential to remove the latest reaction depending on how fast a user selects it. I need some way to have on_raw_reaction_add to wait for the first event to complete before handling the next reaction add.
I took a snippet I saw from this answer from Diggy.
#Check for Duplicate Reaction
#bot.event
async def on_raw_reaction_add(payload): # checks whenever a reaction is added to a message
# Check if the reaction was made by the bot, and if the reaction was done in the voting channel.
if (payload.user_id != bot.user.id and payload.channel_id == vChannel):
#Set channel and message
channel = await bot.fetch_channel(payload.channel_id)
message = await channel.fetch_message(payload.message_id)
# iterating through each reaction in the message
for r in message.reactions:
# checks the reactant isn't a bot and the emoji isn't the one they just reacted with
if payload.member in await r.users().flatten() and not payload.member.bot and str(r) != str(payload.emoji):
# removes the reaction
print('Removing the reaction' + r.emoji)
await message.remove_reaction(r.emoji, payload.member)
else:
print(str(datetime.datetime.now()) + r.emoji + ': not removing')
This removes duplicate reactions as intended, if the user goes slow enough. If the user clicks multiple reactions quickly, the bot loops though and may remove a more recent reaction, instead of keeping the latest one.
I tried to see how to use wait_for but couldn't figure out how to do it.
The best way I have thought to visually represent this is a table:
Reaction 2
Reaction 3
Reaction 5
Add Reaction 2
Check for 1, remove
Add Reaction 3
Check for 2, keep
Check for 1, remove
Add Reaction 5
Check for 3, remove
Check for 2, remove
Check for 1, remove
Check for 4, remove
Check for 3, keep
Check for 2, remove
Check for 5, remove
Check for 4, remove
Check for 3, remove
Check for 6, remove
Check for 5, remove
Check for 4, remove
Check for 7, remove
Check for 6, remove
Check for 5, keep
Check for 8, remove
Check for 7, keep
Check for 6, remove
Check for 9, remove
Check for 8, remove
Check for 7, remove
Check for 10, remove
Check for 9, remove
Check for 8, remove
Check for 10, remove
Check for 9, remove
Check for 10, remove
If you add 2️⃣,3️⃣,5️⃣ quickly, depending on how long it takes to process the check for 2️⃣, it can remove the 3️⃣,5️⃣ reactions. In the example above, if a user reacts with 5️⃣ before the on_raw_reaction_add event for 3️⃣ checks for 5️⃣, 5️⃣ will be removed even though it was the latest reaction.
I need some way to ensure the check/loop completes in sequential order.
Video of the issue, sped up slightly.

Answer 1

The fetch_channel and fetch_message methods are api calls, which can be quite slow.
Rather use Partial Objects (partial messageable and partial message). You can build a cache (or a database). Store a list of user IDs who have voted against the message id of the poll.
In the reaction event, if the user id is already present for the message in the cache, remove the reaction.
bot.poll_cache = {} #Key is message id which you set while creating the poll, Value is a list of user ids. Set it to an empty list
#bot.event
async def on_raw_reaction_add(payload):
user_list = bot.poll_cache.get(payload.message_id)
if user_list is None: #not a poll
return
if not payload.member.bot and payload.member.id in user_list:
pmsg = bot.get_partial_messageable(payload.channel_id).get_partial_message(payload.message_id)
await pmsg.remove_reaction(payload.emoji, payload.member)
else:
user_list.append(payload.member.id)