进行与mysql数据库连接的时候出现错误

# 获取数据库链接
conn = pymysql.connect(host='localhost',
                      user='root',
                      password='123456',
                      db='baike',
                      charset='utf8md4',
                      port=3306)

错误：

Traceback (most recent call last):
  File "E:/GC/imooc/MySQL.py", line 31, in <module>
    port=3306)
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python36-32\lib\site-packages\pymysql\__init__.py", line 90, in Connect
    return Connection(*args, **kwargs)
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python36-32\lib\site-packages\pymysql\connections.py", line 659, in __init__
    self.encoding = charset_by_name(self.charset).encoding
AttributeError: 'NoneType' object has no attribute 'encoding'

尝试多种方法仍然不能够解决