"pymysql.err.InternalError: (1046, u'No database selected')" error message when running Python script from command line
"pymysql.err.InternalError: (1046, u'No database selected')" error message when running Python script from command line
我正在尝试 运行 一个通过 PyMySQL 连接到 MySQL 数据库的 Python 脚本。该脚本有效：
import pymysql
cnx = pymysql.connect(read_default_file = "/directory/my.cnf", cursorclass = pymysql.cursors.DictCursor)
cursor = cnx.cursor()
# Do stuff.
当我在解释器中 运行 脚本时，我没有收到任何错误，但是当我尝试从命令行 运行 它时，我收到以下错误：
Traceback (most recent call last):
File "s02_prepare_data_RNN.py", line 264, in <module>
(omniture, urls, years, global_regions) = get_omniture_data("omniture_results")
File "s02_prepare_data_RNN.py", line 76, in get_omniture_data
sso_to_accountid = get_sso_accountids()
File "s02_prepare_data_RNN.py", line 31, in get_sso_accountids
cursor.execute(query)
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/cursors.py", line 134, in execute
result = self._query(query)
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/cursors.py", line 282, in _query
conn.query(q)
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/connections.py", line 768, in query
self._affected_rows = self._read_query_result(unbuffered=unbuffered)
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/connections.py", line 929, in _read_query_result
result.read()
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/connections.py", line 1125, in read
first_packet = self.connection._read_packet()
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/connections.py", line 893, in _read_packet
packet.check_error()
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/connections.py", line 369, in check_error
err.raise_mysql_exception(self._data)
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/err.py", line 120, in raise_mysql_exception
_check_mysql_exception(errinfo)
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/err.py", line 115, in _check_mysql_exception
raise InternalError(errno, errorvalue)
pymysql.err.InternalError: (1046, u'No database selected')
修改我的代码来自：
import pymysql
cnx = pymysql.connect(read_default_file = "/directory/my.cnf", cursorclass = pymysql.cursors.DictCursor)
cursor = cnx.cursor()
# Do stuff.
至：
import pymysql
cnx = pymysql.connect(read_default_file = "/directory/my.cnf", cursorclass = pymysql.cursors.DictCursor)
cursor = cnx.cursor()
if __name__ == "__main__":
# Do stuff.
修复了错误。我认为 Python 可能会在连接建立之前尝试执行查询，所以我尝试将程序的主要部分放在 if __name__ == "__main__": 下并修复它。不过，我仍然不是 100% 正在发生的事情。我原以为代码会等待建立连接，然后再继续执行以下几行，但此修复表明情况并非如此。
同样值得注意的是，当 运行 来自具有 Python 2.6 的服务器上的命令行的原始脚本时，我才收到错误。当我 运行 本地机器上命令行的原始脚本 Python 2.7 时，我没有得到错误。
总之，if __name__ == "__main__":是不错的Python风格，以后一定会用的
有时，当数据库 URI 构建不正确时，这可能会发生。对我来说，当我的 pymysql 连接字符串 (URL) 如下所示时发生错误：
mysql+pymysql://:@localhost/
要修复它，它需要看起来像：
mysql+pymysql://<my-database-user-name>:@localhost/<my-database-name> # 或将 localhost 替换为您的特定主机名
如果你没有select连接中的数据库，你必须添加这一行。
connection = pymysql.connect(host=DB_host, user=DB_user, password=DB_password) # NO DB_NAME SPECIFED
cursor = connection.cursor()
cursor.execute(f'CREATE DATABASE IF NOT EXISTS {DB_NAME}') # ADD THIS LINE!
connection.select_db(DB_NAME)
我正在尝试 运行 一个通过 PyMySQL 连接到 MySQL 数据库的 Python 脚本。该脚本有效：
import pymysql
cnx = pymysql.connect(read_default_file = "/directory/my.cnf", cursorclass = pymysql.cursors.DictCursor)
cursor = cnx.cursor()
# Do stuff.
当我在解释器中 运行 脚本时，我没有收到任何错误，但是当我尝试从命令行 运行 它时，我收到以下错误：
Traceback (most recent call last):
File "s02_prepare_data_RNN.py", line 264, in <module>
(omniture, urls, years, global_regions) = get_omniture_data("omniture_results")
File "s02_prepare_data_RNN.py", line 76, in get_omniture_data
sso_to_accountid = get_sso_accountids()
File "s02_prepare_data_RNN.py", line 31, in get_sso_accountids
cursor.execute(query)
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/cursors.py", line 134, in execute
result = self._query(query)
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/cursors.py", line 282, in _query
conn.query(q)
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/connections.py", line 768, in query
self._affected_rows = self._read_query_result(unbuffered=unbuffered)
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/connections.py", line 929, in _read_query_result
result.read()
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/connections.py", line 1125, in read
first_packet = self.connection._read_packet()
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/connections.py", line 893, in _read_packet
packet.check_error()
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/connections.py", line 369, in check_error
err.raise_mysql_exception(self._data)
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/err.py", line 120, in raise_mysql_exception
_check_mysql_exception(errinfo)
File "/home/rdu/malcorn/.local/lib/python2.6/site-packages/pymysql/err.py", line 115, in _check_mysql_exception
raise InternalError(errno, errorvalue)
pymysql.err.InternalError: (1046, u'No database selected')
修改我的代码来自：
import pymysql
cnx = pymysql.connect(read_default_file = "/directory/my.cnf", cursorclass = pymysql.cursors.DictCursor)
cursor = cnx.cursor()
# Do stuff.
至：
import pymysql
cnx = pymysql.connect(read_default_file = "/directory/my.cnf", cursorclass = pymysql.cursors.DictCursor)
cursor = cnx.cursor()
if __name__ == "__main__":
# Do stuff.
修复了错误。我认为 Python 可能会在连接建立之前尝试执行查询，所以我尝试将程序的主要部分放在 if __name__ == "__main__": 下并修复它。不过，我仍然不是 100% 正在发生的事情。我原以为代码会等待建立连接，然后再继续执行以下几行，但此修复表明情况并非如此。
同样值得注意的是，当 运行 来自具有 Python 2.6 的服务器上的命令行的原始脚本时，我才收到错误。当我 运行 本地机器上命令行的原始脚本 Python 2.7 时，我没有得到错误。
总之，if __name__ == "__main__":是不错的Python风格，以后一定会用的
有时，当数据库 URI 构建不正确时，这可能会发生。对我来说，当我的 pymysql 连接字符串 (URL) 如下所示时发生错误：
mysql+pymysql://:@localhost/
要修复它，它需要看起来像：
mysql+pymysql://<my-database-user-name>:@localhost/<my-database-name> # 或将 localhost 替换为您的特定主机名
如果你没有select连接中的数据库，你必须添加这一行。
connection = pymysql.connect(host=DB_host, user=DB_user, password=DB_password) # NO DB_NAME SPECIFED
cursor = connection.cursor()
cursor.execute(f'CREATE DATABASE IF NOT EXISTS {DB_NAME}') # ADD THIS LINE!
connection.select_db(DB_NAME)