问题：把一个项目从python2 升级到python3时，发现torndb不能用了。提示如下错误：

  Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/micstu/.local/lib/python3.5/site-packages/torndb.py", line 260, in <module>
  CONVERSIONS[field_type] = [(FLAG.BINARY, str)] + CONVERSIONS[field_type]
  TypeError: can only concatenate list (not "type") to list

原因是：torndb模块是不支持python3.x，所以需要修改部分torndb源码即可正常使用。
1、安装pymysql

    pip install pymysql

2、根据错误找到torndb.py文件

   /home/micstu/.local/lib/python3.5/site-packages/torndb.py

3、修改部分torndb.py代码
1>导入模块

    import  pymysql
    try:
	    import pymysql.connections
	    import pymysql.converters
	    import pymysql.cursors
	    #import MySQLdb.constants
	    #import MySQLdb.converters
	    #import MySQLdb.cursors

2>连接方式

def reconnect(self):
    """Closes the existing database connection and re-opens it."""
    self.close()
    self._db = pymysql.connect(**self._db_args)# self._db = MySQLdb.connect(**self._db_args)
    self._db.autocommit(True)

3>修改连接参数，以及遍历字段类型时所使用的列表增加元素（python3使用append进行元素的添加，而不是使用加号）

#if MySQLdb is not None:
if pymsql is not None:
    # Fix the access conversions to properly recognize unicode/binary
    FIELD_TYPE = pymysql.connections.FIELD_TYPE # FIELD_TYPE = MySQLdb.constants.FIELD_TYPE
    FLAG = pymysql.constants.FLAG#FLAG = MySQLdb.constants.FLAG
    CONVERSIONS = copy.copy(pymysql.converters.conversions)#CONVERSIONS = copy.copy(MySQLdb.converters.conversions)

    field_types = [FIELD_TYPE.BLOB, FIELD_TYPE.STRING, FIELD_TYPE.VAR_STRING]
    if 'VARCHAR' in vars(FIELD_TYPE):
        field_types.append(FIELD_TYPE.VARCHAR)

    for field_type in field_types:
        CONVERSIONS[field_type] = [(FLAG.BINARY,str)].append(CONVERSIONS[field_type])
        #CONVERSIONS[field_type] = [(FLAG.BINARY, str)] + CONVERSIONS[field_type]

    # Alias some common MySQL exceptions
    IntegrityError = pymysql.IntegrityError#IntegrityError = MySQLdb.IntegrityError
    OperationalError = pymysql.OperationalError#OperationalError = MySQLdb.OperationalError

4>修改连接超时时间

def __init__(self, host, database, user=None, password=None,
             max_idle_time=7 * 3600, connect_timeout=10,
             time_zone="+0:00", charset = "utf8", sql_mode="TRADITIONAL"):

5>修改查询方法中的迭代方法（将izip改为zip_longest）

def query(self, query, *parameters, **kwparameters):
    """Returns a row list for the given query and parameters."""
    cursor = self._cursor()
    try:
        self._execute(cursor, query, parameters, kwparameters)
        column_names = [d[0] for d in cursor.description]
        return [Row(itertools.zip_longest(column_names, row))for row in cursor]
        #return [Row(itertools.izip(column_names, row)) for row in cursor]
    finally:
        cursor.close()

测试：