pymysql 连接选择查询和 fetchall 返回具有像 b'25.00' 这样的字节文字而不是像 '25.00' 这样的字符串的元组

Question

我有一个python script，它只在使用pymysql 连接到我在Windows 8.1 上具有MySQL 5.6database 的本地测试机器时运行良好。 Select query / fetchal() 返回像 ('1', '2015-01-02 23:11:19', '25.00') 这样的元组。

但是，当我使用稍微修改的相同脚本以包含到在 Linux 服务器上运行的远程 MySQL 5.0.96 生产数据库的第二个连接时，它会返回 tuples，例如 (b'1', b'2015- 01-02 23:11:19', b'25.00') 并且脚本无法正确运行，因为匹配条件和使用返回元组的查询失败。

知道为什么，我怎样才能让它返回tuples，其列值没有“b”前缀？

Answer 1

我通过以下解决方法解决了这个问题。它涉及处理从远程数据库列返回的字节文字，如下面的示例所示，我创建该示例来解释答案。

conn = pymysql.connect(host=myHost, port=myPort, user=myUser, passwd=myPassword, database=myDatabase, charset="utf8")
cur = conn.cursor()

theDateTime = re.sub( r' ', '-', str(datetime.now()))
theDateTime = theDateTime[0:10] + " " + theDateTime[11:19]

productName = 'abc'
myMaxPrice = 100.0

try:
    # The below query to the remote database returned tuples like (b'1', b'2015-01-02 23:11:19', b'25.00') for MySQL DB tableA columns: ID, date_changed, price
    query = "SELECT IFNULL(ID,''), IFNULL(date_changed,''), IFNULL(price, '') FROM tableA WHERE product = '" + productName + "';"   
    cur.execute(query)
    for r in cur.fetchall():
        # Given the returned result tuple r[] from the remote DB included byte literals instead of strings, I had to encode the '' strings in the condition below to make them byte literals
        # However, I did not have to encode floats like mMaxyPrice and float(r[2]) as they were not a string; float calculations were working fine, even though the returned float values were also byte literals within the tuple
        if not r[1] and float(r[2]) >= myMaxPrice: 
            #Had to encode and then decode r[0] below due to the ID column value r[0] coming back from the remote DB query / fetchall() as a byte literal with a "b" prefix
            query = "UPDATE tableA SET date_changed = '" + theDateTime + "', price = " + str(myMaxPrice) + " WHERE ID = " + r[0].decode(encoding='utf-8') + ";"  
            cur.execute(query)
            conn.commit()
except pymysql.Error as e:
    try:
        print("\nMySQL Error {0}: {1}\n".format(e.args[0], e.args[1]))
    except IndexError:
        print("\nMySQL Index Error: {0}\n".format(str(e)))
    print("\nThere was a problem reading info from the remote database!!!\n") 

感谢 m170897017 指出这些是字节文字，并感谢 Neha Shukla 帮助澄清。尽管我仍然有兴趣弄清楚为什么远程数据库返回字节文字，而不是本地数据库返回的字符串。我需要使用某种编码来连接到远程数据库吗？如何使用？是远程数据库中使用的旧版本的 MySQL 导致的吗？这是Linux远程与Windows本地的区别吗？或者是引入字节文字的 fetchall() 函数？如果有人知道，请提供它以帮助我进一步理解这一点。

Answer 2

b 前缀表示 Python3 中的字节文字。尝试将其转换为字符串。

...
res = (b'1', b'2015-01-02 23:11:19', b'25.00')
new_res = []
for i in res:
    new_res.append(i.decode(encoding='utf-8'))

new_res = tuple(new_res)
...