pymysql KeyError:255

摘要：在项目新建所有的表时遇到的错误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使用方法更新导致上述问题的主要原因可能是这个错误主要原因是更新了很多字符集，但是这些字符集长度超过了，所以旧版

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 
    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://:@:/")

(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 FilesPython36libsite-packagespymysql\__init__.py", line 90, in Connect
    return Connection(*args, **kwargs)
  File "C:Program FilesPython36libsite-packagespymysqlconnections.py", line 706, in __init__
    self.connect()
  File "C:Program FilesPython36libsite-packagespymysqlconnections.py", line 931, in connect
    self._get_server_information()
  File "C:Program FilesPython36libsite-packagespymysqlconnections.py", line 1269, in _get_server_information
    self.server_charset = charset_by_id(lang).name
  File "C:Program FilesPython36libsite-packagespymysqlcharset.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/Py...
https://github.com/PyMySQL/Py...
https://github.com/PyMySQL/Py...