为什么“if in”语句不适用于discord.py？

Question

I have the following code for a Discord bot I am working on:

import discord
import random 
from discord.ext import commands, tasks
import os
import time
import asyncio
import re
import urllib.request
import json
from apiclient.discovery import build
from itertools import product, cycle
from discord.ext.tasks import loop

client = commands.Bot(command_prefix =  'v!', description='fff', case_insensitive=True)

token = 'REDEACTED'
client.remove_command("help")

@client.command(pass_context=True)
async def Ban(ctx):

    members = []

    a = (ctx.author)
    print(a)

    m = (ctx.message.content)

    m = m.replace("v!ban ", '')
    print(m)

    with open('members.txt', 'w'): pass

#    print(members)
    for member in ctx.guild.members:

        with open('members.txt', 'a', encoding = "UTF-8") as f:
            f.writelines(str(member) + '\n')

    with open('members.txt', 'r', encoding = "UTF-8") as f:
        members = f.read()

    for i in members:
        if i == m:
            print('True')
        else:
            print("False")

@client.event
async def on_ready():
    print('Logged in as')
    print(client.user.name)
    print(client.user.id)
    print('------')
    await client.change_presence(activity = discord.Game("v!help"))

client.run(token)

The 'members.txt' file contains: (members of my Discord server)

kurt#6396
galen#2172
xXDEFECTMEXx#0598
xx_kyrah.w#2995
lmao.com#5953
skyanite#1725
Gilly#5865
chef shaq#3889
mariokuhl.RS#0101
UltimateDucc#9121
xSaltyOne#9450
Jacobs Kid#0771
Alex L#7988
✪ csw ✪#0115
smithers#4004
Little5avage#8028
FaZe_Eric#9627
Unib_Rovodkalan#8661

ARX6.#5773
The Bomb#3693

If I was to do the command v!ban UltimateDucc#9121 , it would return False instead of True , even though this value is present in the array.

What I'm trying to achieve:

Gather server members - Done

Put into file - Done

Get input from user - Done

Check if input is in file - Stuck

Any help is appreciated.

Answer 1

f.read() will return a string with the contents of the file.
When you loop through it, i will be each character in that string.

You should use list(f) or f.readlines() and strip the newline at the end instead

See https://docs.python.org/3/tutorial/inputoutput.html#methods-of-file-objects for more information.

Answer 2

Comments added for clarification but your base problem was that you were iterating over all of the characters in your loaded list from the file and checking if each one of them was equal to the string provided by the user.

@client.command(pass_context=True)
async def Ban(ctx):

    members = []

    a = (ctx.author)
    print(a)

    m = (ctx.message.content)

    m = m.replace("v!ban ", '')
    print(m)

    with open('members.txt', 'w'): pass

    # I swapped the order here because otherwise the file gets opened each iteration
    with open('members.txt', 'a', encoding = "UTF-8") as f:
        for member in ctx.guild.members:
            f.write(str(member) + '\n') # you don't have to use writelines here because you are only writing a single line

    with open('members.txt', 'r', encoding = "UTF-8") as f:
        members = f.read().split('\n') # we want a list of members, not a string containing all of them

    # we can just use the "in" operator here, it checks if our string is in the loaded list
    if m in members:
        print('True')
    else:
        print("False")

Answer 3

Do not use this:

# code block 1
for i in members:
    if i == m:
        print('True')
    else:
        print("False")

Use this:

# code block 2
if i in members:
    print('true')
else:
    print('false')

or

Use this:

# code block 3 
x = members.split('\n')
if i in members:
    print('true')
else:
    print('false')

In code block 1: Comparisons are done character by character. You are comparing each character in the file to the string entered by user.

In code block 2: Python looks for a substring the in the given string. ie: It'll return True if the string entered by the user is present in the content of the file.

In code block 3: Split the content of the file up line by line and store each entry in an array. Then look if the string entered by the user is there in this array.