执行sql后，出现Assertion failed

code:

import pytest
import pymysql
# 操作数据库

conn = pymysql.connect(
    user='root',
    passwd='123456',
    host='localhost',
    port=3306,
    db='my_test'
)
def test_db():
    qs = 'select uid,uname,pwd from test_user'
    lst = []
    try:
        cursor = conn.cursor()
        cursor.execute(qs)
        # 获取所有的数据
        r = cursor.fetchall()
        for x in r:
            # x 表示列
            u = (x[0],x[1],x[2])
            lst.append(u)
        return lst
    finally:
        cursor.close()
        conn.close()

@pytest.mark.parametrize('uid,uname,pwd',test_db())
def test04(uid,uname,pwd):
    print(uid,uname,pwd)

if __name__ == '__main__':
    pytest.main(['-vs', 'test_file.py'])

控制台

Testing started at 11:10 ...
D:\TestSoftware\Anaconda3\python.exe "D:\TestSoftware\PyCharm\PyCharm Community Edition 2020.1.3\plugins\python-ce\helpers\pycharm\_jb_pytest_runner.py" --path D:/TestSoftware/PyCharm/PyCharmProject/Jpress/Cases/ddt/test_file.py
Launching pytest with arguments D:/TestSoftware/PyCharm/PyCharmProject/Jpress/Cases/ddt/test_file.py in D:\TestSoftware\PyCharm\PyCharmProject\Jpress\Cases\ddt

============================= test session starts =============================
platform win32 -- Python 3.7.4, pytest-5.2.1, py-1.8.0, pluggy-0.13.0 -- D:\TestSoftware\Anaconda3\python.exe
cachedir: .pytest_cache
rootdir: D:\TestSoftware\PyCharm\PyCharmProject\Jpress\Cases\ddt
plugins: allure-pytest-2.8.18, arraydiff-0.3, dependency-0.5.1, doctestplus-0.4.0, openfiles-0.4.0, remotedata-0.3.2
collecting ... collected 4 items

test_file.py::test_db FAILED                                             [ 25%]
test_file.py:60 (test_db)
def test_db():
        qs = 'select uid,uname,pwd from test_user'
        lst = []
        try:
            cursor = conn.cursor()
>           cursor.execute(qs)

test_file.py:66: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pymysql.cursors.Cursor object at 0x000001FC4322A5C8>
query = 'select uid,uname,pwd from test_user', args = None

    def execute(self, query, args=None):
        """Execute a query
    
        :param str query: Query to execute.
    
        :param args: parameters used with query. (optional)
        :type args: tuple, list or dict
    
        :return: Number of affected rows
        :rtype: int
    
        If args is a list or tuple, %s can be used as a placeholder in the query.
        If args is a dict, %(name)s can be used as a placeholder in the query.
        """
        while self.nextset():
            pass
    
        query = self.mogrify(query, args)
    
>       result = self._query(query)

..\..\..\..\..\Anaconda3\lib\site-packages\pymysql\cursors.py:163: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pymysql.cursors.Cursor object at 0x000001FC4322A5C8>
q = 'select uid,uname,pwd from test_user'

    def _query(self, q):
        conn = self._get_db()
        self._last_executed = q
        self._clear_result()
>       conn.query(q)

..\..\..\..\..\Anaconda3\lib\site-packages\pymysql\cursors.py:321: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pymysql.connections.Connection object at 0x000001FC4308F048>
sql = b'select uid,uname,pwd from test_user', unbuffered = False

    def query(self, sql, unbuffered=False):
        # if DEBUG:
        #     print("DEBUG: sending query:", sql)
        if isinstance(sql, text_type) and not (JYTHON or IRONPYTHON):
            if PY2:
                sql = sql.encode(self.encoding)
            else:
                sql = sql.encode(self.encoding, 'surrogateescape')
>       self._execute_command(COMMAND.COM_QUERY, sql)

..\..\..\..\..\Anaconda3\lib\site-packages\pymysql\connections.py:504: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pymysql.connections.Connection object at 0x000001FC4308F048>
command = 3, sql = b'select uid,uname,pwd from test_user'

    def _execute_command(self, command, sql):
        """
        :raise InterfaceError: If the connection is closed.
        :raise ValueError: If no username was specified.
        """
        if not self._sock:
>           raise err.InterfaceError(0, '')
E           pymysql.err.InterfaceError: (0, '')

..\..\..\..\..\Anaconda3\lib\site-packages\pymysql\connections.py:742: InterfaceError

During handling of the above exception, another exception occurred:

    def test_db():
        qs = 'select uid,uname,pwd from test_user'
        lst = []
        try:
            cursor = conn.cursor()
            cursor.execute(qs)
            # 获取所有的数据
            r = cursor.fetchall()
            for x in r:
                # x 表示列
                u = (x[0],x[1],x[2])
                lst.append(u)
            return lst
        finally:
            cursor.close()
>           conn.close()

test_file.py:76: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pymysql.connections.Connection object at 0x000001FC4308F048>

    def close(self):
        """
        Send the quit message and close the socket.
    
        See `Connection.close() <https://www.python.org/dev/peps/pep-0249/#Connection.close>`_
        in the specification.
    
        :raise Error: If the connection is already closed.
        """
        if self._closed:
>           raise err.Error("Already closed")
E           pymysql.err.Error: Already closed

..\..\..\..\..\Anaconda3\lib\site-packages\pymysql\connections.py:356: Error

test_file.py::test04[1-tom-123] 
test_file.py::test04[2-kite-123] 
test_file.py::test04[3-rows-456] 

================================== FAILURES ===================================
___________________________________ test_db ___________________________________

    def test_db():
        qs = 'select uid,uname,pwd from test_user'
        lst = []
        try:
            cursor = conn.cursor()
>           cursor.execute(qs)

test_file.py:66: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pymysql.cursors.Cursor object at 0x000001FC4322A5C8>
query = 'select uid,uname,pwd from test_user', args = None

    def execute(self, query, args=None):
        """Execute a query
    
        :param str query: Query to execute.
    
        :param args: parameters used with query. (optional)
        :type args: tuple, list or dict
    
        :return: Number of affected rows
        :rtype: int
    
        If args is a list or tuple, %s can be used as a placeholder in the query.
        If args is a dict, %(name)s can be used as a placeholder in the query.
        """
        while self.nextset():
            pass
    
        query = self.mogrify(query, args)
    
>       result = self._query(query)

..\..\..\..\..\Anaconda3\lib\site-packages\pymysql\cursors.py:163: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pymysql.cursors.Cursor object at 0x000001FC4322A5C8>
q = 'select uid,uname,pwd from test_user'

    def _query(self, q):
        conn = self._get_db()
        self._last_executed = q
        self._clear_result()
>       conn.query(q)

..\..\..\..\..\Anaconda3\lib\site-packages\pymysql\cursors.py:321: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pymysql.connections.Connection object at 0x000001FC4308F048>
sql = b'select uid,uname,pwd from test_user', unbuffered = False

    def query(self, sql, unbuffered=False):
        # if DEBUG:
        #     print("DEBUG: sending query:", sql)
        if isinstance(sql, text_type) and not (JYTHON or IRONPYTHON):
            if PY2:
                sql = sql.encode(self.encoding)
            else:
                sql = sql.encode(self.encoding, 'surrogateescape')
>       self._execute_command(COMMAND.COM_QUERY, sql)

..\..\..\..\..\Anaconda3\lib\site-packages\pymysql\connections.py:504: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pymysql.connections.Connection object at 0x000001FC4308F048>
command = 3, sql = b'select uid,uname,pwd from test_user'

    def _execute_command(self, command, sql):
        """
        :raise InterfaceError: If the connection is closed.
        :raise ValueError: If no username was specified.
        """
        if not self._sock:
>           raise err.InterfaceError(0, '')
E           pymysql.err.InterfaceError: (0, '')

..\..\..\..\..\Anaconda3\lib\site-packages\pymysql\connections.py:742: InterfaceError

During handling of the above exception, another exception occurred:

    def test_db():
        qs = 'select uid,uname,pwd from test_user'
        lst = []
        try:
            cursor = conn.cursor()
            cursor.execute(qs)
            # 获取所有的数据
            r = cursor.fetchall()
            for x in r:
                # x 表示列
                u = (x[0],x[1],x[2])
                lst.append(u)
            return lst
        finally:
            cursor.close()
>           conn.close()

test_file.py:76: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pymysql.connections.Connection object at 0x000001FC4308F048>

    def close(self):
        """
        Send the quit message and close the socket.
    
        See `Connection.close() <https://www.python.org/dev/peps/pep-0249/#Connection.close>`_
        in the specification.
    
        :raise Error: If the connection is already closed.
        """
        if self._closed:
>           raise err.Error("Already closed")
E           pymysql.err.Error: Already closed

..\..\..\..\..\Anaconda3\lib\site-packages\pymysql\connections.py:356: Error
========================= 1 failed, 3 passed in 0.30s =========================

Process finished with exit code 1
PASSED                                   [ 50%]1 tom 123
PASSED                                  [ 75%]2 kite 123
PASSED                                  [100%]3 rows 456

Assertion failed

Assertion failed