pymysql KeyError:255

在weibospider项目新建所有的表时遇到的错误：

Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/sqlalchemy/pool.py", line 1122, in _do_get
    return self._pool.get(wait, self._timeout)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/sqlalchemy/util/queue.py", line 145, in get
    raise Empty
sqlalchemy.util.queue.Empty

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "create_all.py", line 10, in <module>
    create_all_table()
  File "create_all.py", line 7, in create_all_table
    metadata.create_all()
  ...

没有找到出错的具体原因，所以只能更换一个引擎，在这里找到了一个临时方案：
安装新的引擎：

 $ pip install mysql-connector-python

使用方法：

 Engine = create_engine('mysql+mysqlconnector://<USERNAME>:<PASSWD>@<HOSTNAME>:<PORT>/<DBNAME>')

(2018.5.3更新)
导致上述问题的主要原因可能是KeyError: 255这个错误：

Traceback (most recent call last):
  ...
  File "C:\Program Files\Python36\lib\site-packages\pymysql\__init__.py", line 90, in Connect
    return Connection(*args, **kwargs)
  File "C:\Program Files\Python36\lib\site-packages\pymysql\connections.py", line 706, in __init__
    self.connect()
  File "C:\Program Files\Python36\lib\site-packages\pymysql\connections.py", line 931, in connect
    self._get_server_information()
  File "C:\Program Files\Python36\lib\site-packages\pymysql\connections.py", line 1269, in _get_server_information
    self.server_charset = charset_by_id(lang).name
  File "C:\Program Files\Python36\lib\site-packages\pymysql\charset.py", line 38, in by_id
    return self._by_id[id]
KeyError: 255

主要原因是MySQL8.0更新了很多字符集，但是这些字符集长度超过255了，所以旧版的PyMySQL不支持长度超过255的字符
查看当前版本的PyMySQL：

> pip list
Package                Version
---------------------- -----------
PyMySQL                0.7.11

更新PyMySQL：

> pip install --upgrade PyMySQL
Collecting PyMySQL
  Downloading https://files.pythonhosted.org/packages/e5/07/c0f249aa0b7b0517b5843eeab689b9ccc6a6bb0536fc9d95e65901e6f2ac/PyMySQL-0.8.0-py2.py3-none-any.whl (83kB)
    100% |████████████████████████████████| 92kB 453kB/s
Installing collected packages: PyMySQL
  Found existing installation: PyMySQL 0.7.11
    Uninstalling PyMySQL-0.7.11:
      Successfully uninstalled PyMySQL-0.7.11
Successfully installed PyMySQL-0.8.0

相关内容：

• https://github.com/PyMySQL/PyMySQL/pull/591
• https://github.com/PyMySQL/PyMySQL/pull/592
• https://github.com/PyMySQL/PyMySQL/pull/577