Question

我只有python script才能正常运行，仅使用MySQL 5.6连接连接到Windows 8.1 pymysql数据库的本地测试计算机。 Select query / fetchal()返回元组，如（'1'，'2015-01-02 23:11:19'，'25 .00'）。

但是，当我使用略微修改的相同脚本来包含与MySQL 5.0.96服务器上运行的远程Linux生产数据库的第二个连接时，它返回tuples之类的（b'1 '，b'2015-01-02 23:11:19'，b'25.00'）并且脚本无法正常运行，因为匹配条件和使用返回的元组的查询失败。

知道原因，以及如何让它返回tuples，其列值没有“b”前缀？

Answer 1

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)
...

Answer 2

我通过以下方法解决了这个问题。它涉及处理远程数据库列中返回的字节文字，如下面的示例所示，我创建该文字来解释答案。

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指出这些字节文字，并感谢Neha Shukla帮助澄清。我仍然会感兴趣的是找出远程数据库返回字节文字的原因，而不是本地数据库返回的字符串。是否需要使用某种编码来连接远程数据库以及如何使用？是远程数据库中使用的旧版MySQL导致它吗？这是Linux远程对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，请发言，以帮助我进一步了解这一点。

pymysql连接选择查询和fetchall返回元组，它有像b'25.00'这样的字节文字，而不是像'25 .00'那样的字符串

2 个答案: