Question

为了在python中使用不和谐的重写分支制作齿轮，我遇到了一些麻烦。

我正在尝试发出命令以使用mysql连接器启动到数据库的连接并创建一个简单表。问题是当我定义一个游标变量，如官方mysql文档中所述时，出现错误： “分配前已引用本地变量'cnx'”

现在这是代码：

import discord
from discord.ext import commands
import json
import asyncio
import mysql.connector
from mysql.connector import errorcode

with open("config.json") as configfile:
    config = json.load(configfile)

class testcog:

    def __init__(self, client):
        self.client = client


    @commands.command()
    async def dbconnect(self, ctx):
        await ctx.message.author.send('I\'m connecting to the database, please be patient.')

        try:
            cnx = mysql.connector.connect(user=config['sqlconfig']['user'], password=config['sqlconfig']['password'],
                                          host=config['sqlconfig']['host'],
                                          database=config['sqlconfig']['database'])
        except mysql.connector.Error as err:
            if err.errno == errorcode.ER_ACCESS_DENIED_ERROR:
                print("Something is wrong with your user name or password")
            elif err.errno == errorcode.ER_BAD_DB_ERROR:
                print("Database does not exist")
            else:
                print(err)
        else:
            cnx.close()

        cursor = cnx.cursor()

        TABLES = {}
        TABLES['employee'] = (
            "CREATE TABLE `employee` ("
            "  `emp_no` int(11) NOT NULL AUTO_INCREMENT,"
            "  `birth_date` date NOT NULL,"
            "  `first_name` varchar(14) NOT NULL,"
            "  `last_name` varchar(16) NOT NULL,"
            "  `gender` enum('M','F') NOT NULL,"
            "  `hire_date` date NOT NULL,"
            "  PRIMARY KEY  (`emp_no`)"
            ") ENGINE=InnoDB")

        for table_name in TABLES:
            table_description = TABLES[table_name]
            try:
                print("Creating table {}: ".format(table_name), end='')
                cursor.execute(table_description)
            except mysql.connector.Error as err:
                if err.errno == errorcode.ER_TABLE_EXISTS_ERROR:
                    print("already exists.")
                else:
                    print(err.msg)
            else:
                print("OK")

        cursor.close()
        cnx.close()


def setup(client):
    client.add_cog(testcog(client))

该表及其创建代码直接从官方文档中复制而来。出现错误的代码片段是：cursor = cnx.cursor()字典创建之前的TABLES。

我不明白自己在做什么，非常感谢您的帮助。

Answer 1

我想我可以为您提供一些帮助！

在 cog 文件中工作时，您需要在主类中继承 commands.Cog。除此之外，您应该异步打开和关闭您的 json 文件。

我们使用异步和 discord.py 来实现，这样如果多人使用您的命令，机器人就不会得到备份（这样机器人可以一次做多件事）。 MySql 有一个异步库，还有一个用于打开 json 文件的异步库，让我们来看看如何使用它们。

您可以在此处查看 aiomysql 文档：https://aiomysql.readthedocs.io/en/latest/

让我们着手解决您的问题。为了做到这一点，我们需要确保为我们的数据库设置了机器人。我们设置了一个叫做“池”的东西，它随着数据库的变化而变化。

我将向您展示我在此示例中的文件结构：

main.py
/cogs
   testcog.py

# When creating our bot, we want to setup our db (database) connection, so we can reference it later

from discord.ext import commands
import discord
import aiomysql
import asyncio
import aiofiles, json

loop = asyncio.get_event_loop()

bot = commands.Bot(command_prefix = "!", intents=discord.Intents.all())

@bot.event
async def on_ready():
    config = json.loads(await(await aiofiles.open("/home/pi/Desktop/Experimental/prestagingapi.json")).read())
    bot.pool = await aiomysql.create_pool(host=config['sqlconfig']['host'], port = 0000, user = config['sqlconfig']['user'], 
                                        password = config['sqlconfig']['password'], 
                                        db = config['sqlconfig']['database'], loop=loop)
    print("Bot is online!")


# We need to load our cogs and setup our db loop to reference it later
initial_extension = (
    "cogs.testcog",
)

for extension in initial_extension:
    bot.load_extension(extension)

bot.run("YOUR_TOKEN", reconnect=True)

现在，我们可以在我们的齿轮内部工作来设置一切。我将这个齿轮的文件命名为 testcog.py 文件夹内的 cogs。

import discord
from discord.ext import commands


class testCog(commands.Cog): # I defined that our class inherits the cog for discords
    def __init__(self, bot):
        self.bot = bot

    @commands.command()
    async def create_table(self, ctx):
        await ctx.author.send('I\'m connecting to the database, please be patient.') #ctx.message.author is ctx.author

        # now you can create your db connection here:
        # looking at the aiomysql documentation, we can create a connection and execute what we need
        async with self.bot.pool.acquire() as conn:
            async with conn.cursor() as cur:
                # in order to execute something (creaing a table for ex), we can do this:
                await cur.execute()

def setup(bot): # every cog needs a setup function
    bot.add_cog(testCog(bot))

在课堂上分配之前引用了局部变量？与python，不和谐

1 个答案: