TypeError：元组索引必须是整数或切片，而不是 str postgres/python

Question

您好，我正在尝试从我的 postgres 数据库中名为 time 的行中获取时间戳，但出现错误。这是数据库中的第二行。

错误TypeError: tuple indices must be integers or slices, not str 位于stamp = cursor.fetchone()["time"] 行。

我希望在我的不和谐机器人中将元组读取为字符串。这是我正在处理的内容：

for member in guild.members:
        cursor = conn.cursor()
        cursor.execute("SELECT time FROM blacklist WHERE username=%s", (member.id, ))
        stamp = cursor.fetchone()["time"]
        for time in stamp: 
            if time is not None:
                timestamp = time
                members = discord.utils.get(member.guild.roles, name="Members")
                restricted_role = get(guild.roles, name="Restricted")
                datestamp = datetime.now()
                datetimestring = str(datestamp.now().strftime("%Y%m%d%H%M%S"))
                dateonlystring = timestamp.strftime("%Y%m%d%H%M%S")
        
                if (datetimestring > dateonlystring):
                    await member.add_roles(members)
                    await member.remove_roles(restricted_role)
                    print("Done.")

我们将不胜感激。

Answer 1

此代码 sn-p 存在一些问题。引发此错误的是cursor.fetchone() 返回tuple，而不是错误提示的dict。您需要在返回定义中为其指定与名为“time”的列相对应的整数索引，这应该是 0。

所以你需要换行：

stamp = cursor.fetchone()["time"]

到

stamp = cursor.fetchone()[0]

在psychopg.fetchone()查看详情

但是，我注意到 stamp 应该被编入索引，所以即使您测试 None 也会失败。

我在修改后的代码中提出了其他建议，基于它的推测。

for member in guild.members:
        cursor = conn.cursor()

        # Changed the query so that NULLs (which will be cast as None) are not returned
        cursor.execute("SELECT time FROM blacklist WHERE username=%s AND time IS NOT NULL", (member.id, ))

        # no index needed, multiple stamps are returned 
        results = cursor.fetchall()

        for result in results:
            # first and only returned element
            timestamp = result[0] 

            members = discord.utils.get(member.guild.roles, name="Members")
            restricted_role = get(guild.roles, name="Restricted")
            datestamp = datetime.now()

            datetimestring = str(datestamp.now().strftime("%Y%m%d%H%M%S"))
            dateonlystring = timestamp.strftime("%Y%m%d%H%M%S")
        
            if (datetimestring > dateonlystring):
                    await member.add_roles(members)
                    await member.remove_roles(restricted_role)
                    print("Done.")