Python 调用 MySQL 语句报错：TypeError: 'NoneType' object is not subscriptable，如何解决？

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python 调用 mysql 语句报错

有开发者在调用 mysql 语句时遇到了报错，如图所示：

 traceback (most recent call last):
  file "/users/a/pycharmprojects/untitled1/main.py", line 20, in <module>
    cur.execute("select * from user where username=%s and password=%s", [username, password])
  file "/usr/local/cellar/python@3.9/3.9.0_1/frameworks/python.framework/versions/3.9/lib/python3.9/site-packages/mysql/connector/cursor.py", line 677, in execute
    return self._handle_result(self._connection.cmd_query(stmt, raw=self._raw,
  file "/usr/local/cellar/python@3.9/3.9.0_1/frameworks/python.framework/versions/3.9/lib/python3.9/site-packages/mysql/connector/connection.py", line 1001, in cmd_query
    result = self._send_cmd(servercmd.query, query)
  file "/usr/local/cellar/python@3.9/3.9.0_1/frameworks/python.framework/versions/3.9/lib/python3.9/site-packages/mysql/connector/connection.py", line 869, in _send_cmd
    self._executed = conn.cmd_query(stmt)
  file "/usr/local/cellar/python@3.9/3.9.0_1/frameworks/python.framework/versions/3.9/lib/python3.9/site-packages/mysql/connector/connection.py", line 1001, in cmd_query
    result = self._send_cmd(servercmd.query, query)
  file "/usr/local/cellar/python@3.9/3.9.0_1/frameworks/python.framework/versions/3.9/lib/python3.9/site-packages/mysql/connector/connection.py", line 939, in _send_cmd
    self._handle_error(error)
  file "/usr/local/cellar/python@3.9/3.9.0_1/frameworks/python.framework/versions/3.9/lib/python3.9/site-packages/mysql/connector/connection.py", line 928, in _handle_error
    if deferred is false and is_fatal:
typeerror: 'nonetype' object is not subscriptable

这个问题的原因是 %s 没有加上双引号，正确的写法应该是：

cur.execute("select * from user where username=\"%s\" and password=\"%s\"", [username, password])

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