错误：PyQt5 中的“驱动程序未加载”

Question

我即将将 PyQt5 连接到 MySQL。不幸的是，我收到错误“未加载驱动程序”。 Python 说驱动程序在里面：

from PyQt5.QtSql import QSqlDatabase
print(list(map(str, QSqlDatabase.drivers())))

答案：['QSQLITE', 'QMYSQL', 'QMYSQL3', 'QODBC', 'QODBC3', 'QPSQL', 'QPSQL7'] 我使用的是 Windows 7 并安装了 Qt Designer

这是我的代码：

from PyQt5.QtSql import QSqlDatabase, QSqlQuery, QSqlTableModel
from PyQt5.QtWidgets import QTableView, QApplication
import sys
app = QApplication(sys.argv)
db = QSqlDatabase.addDatabase('QMYSQL')
db.setHostName('****')
db.setDatabaseName('****')
db.setUserName('****')
db.setPassword('****')
ok = db.open()
if not ok: print(db.lastError().text())
else: print("connected")
query = QSqlQuery(db);
query.exec_('SELECT * FROM tbl_Customers');

谁有这方面的经验。非常感谢

Answer 1

我通过安装 PyQt5 的 12.0 版而不是 14 版解决了这个问题。 如果您将 libmysql.dll 的副本放在项目文件夹中也可能会有所帮助

Answer 2

从提升的命令提示符运行：

o 任何一个：pip install --only-binary :all: mysqlclient
o 或者：首先安装构建工具https://visualstudio.microsoft.com/downloads/#build-tools-for-visual-studio-2017 然后运行：pip install mysqlclient）（这个选项需要你下载一个4gb+的文件）

完成后，您可以像这样连接：

from PyQt5 import QtSql
import mysql.connector

class DbConnection(object):
    def connect(self):
        try:
            self.__db = QtSql.QSqlDatabase.addDatabase("QMYSQL")
            self.__db.setHostName("localhost")
            self.__db.setDatabaseName("yourDB")
            self.__db.setUserName("root")
            self.__db.setPassword("yourPassword")
            self.__ok = self.__db.open()
        except:
            print(self.__db.lastError().text())

        return self.__ok

    def closeConnection(self):
        try:
            self.__db.close()
        except:
            pass

if __name__ == "__main__":
    from PyQt5 import QtWidgets
    import sys
    app = QtWidgets.QApplication(sys.argv)

    conn = DbConnection()
    print("Connected: " + str(conn.connect()))
    conn.closeConnection()

    sys.exit(app.exec_())

Answer 3

我像这样将 PyQt5 连接到 MySQL：

from PyQt5       import QtCore, QtGui, QtWidgets
#from PyQt5.QtSql import QSqlDatabase, QSqlQuery
import MySQLdb   as mysql                  # pip install mysqlclient        


def convert(in_data):
    def cvt(data):
        try:
            return ast.literal_eval(data)
        except Exception:
            return str(data)
    return tuple(map(cvt, in_data))


class Ui_MainWindow(object):

    def loadconection(self):
        #                        HostName     UserName           Password      DatabaseName
        db = mysql.connect(host="localhost",user="user", passwd="password",db="testdb")
        with db:
            cur = db.cursor()
            #                             table vvvvvvvvv         
            rows = cur.execute("""select * from pyqt5data""")
            data = cur.fetchall()

            for row in data:
                self.add_table(convert(row))

            cur.close()

    def add_table(self, columns):
        rowPosition = self.tableWidget.rowCount()
        self.tableWidget.insertRow(rowPosition)         
        for i, column in enumerate(columns):
            self.tableWidget.setItem(rowPosition, i, QtWidgets.QTableWidgetItem(str(column)))

    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(800, 520)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.tableWidget = QtWidgets.QTableWidget(self.centralwidget)
        self.tableWidget.setGeometry(QtCore.QRect(35, 21, 731, 401))
        self.tableWidget.setColumnCount(5)
        self.tableWidget.setHorizontalHeaderLabels(['Id', 'Name', 'Email', 'Phone', 'Note'])
        self.tableWidget.setObjectName("tableWidget")
        self.tableWidget.setAlternatingRowColors(True)
        self.tableWidget.horizontalHeader().setSectionResizeMode(QtWidgets.QHeaderView.Stretch)

        self.btn_abrirbd2 = QtWidgets.QPushButton(self.centralwidget)
        self.btn_abrirbd2.setGeometry(QtCore.QRect(340, 460, 75, 23))
        self.btn_abrirbd2.setObjectName("btn_abrirbd2")
        self.btn_abrirbd2.clicked.connect(self.loadconection)

        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.btn_abrirbd2.setText(_translate("MainWindow", "SELECT mysql"))

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

Answer 4

问题出在应用程序启动过程中。对于 PyQt，您需要启动一个 GUI 应用程序，然后才能真正使用它下面的类。要记住的另一件事是，始终尝试查看实际错误。在您的情况下，您正在强制使用 lastError() 方法并且在此之前错过了一些有价值的点。您只看到Driver not loaded 错误。但是之前那个终端也显示QSqlDatabase: an instance of QCoreApplication is required for loading driver plugins这个错误，清楚地说明了驱动找不到的实际原因。

要制作一个 QCoreApplication，你需要在你的代码中添加这个 -

if __name__ == '__main__':
   app = QApplication(sys.argv)

所以你的代码可以是 -

from PyQt5.QtSql import QSqlDatabase, QSqlQuery, QSqlTableModel
from PyQt5.QtWidgets import QTableView, QApplication
import sys


def dbcon():
    db = QSqlDatabase.addDatabase('QMYSQL')
    db.setHostName('****')
    db.setDatabaseName('****')
    db.setUserName('****')
    db.setPassword('****')
    ok = db.open()
    if not ok: print(db.lastError().text())
    # else: print("connected")
    query = QSqlQuery(db)
    query.exec_('SELECT * FROM tbl_Customers')


if __name__ == '__main__':
    app = QApplication(sys.argv)
    dbcon()

我用 SQlite 数据库做了一个示例，因为我没有配置 MySql。演示 -

from PyQt5.QtSql import QSqlDatabase, QSqlQuery, QSqlTableModel
from PyQt5.QtWidgets import QTableView, QApplication, QMessageBox


def createDB():
    db = QSqlDatabase.addDatabase('QSQLITE')
    db.setDatabaseName('sports.db')
    if not db.open():
        QMessageBox.critical(None, ("Cannot open database"),
                                   ("Unable to establish a database connection.\n"
                                                 "This example needs SQLite support. Please read "
                                                 "the Qt SQL driver documentation for information "
                                                 "how to build it.\n\n"
                                                 "Click Cancel to exit."),
                                   QMessageBox.Cancel)
    return False

    query = QtSql.QSqlQuery()
    query.exec_("create table sportsmen(id int primary key, "
                "firstname varchar(20), lastname varchar(20))")
    query.exec_("insert into sportsmen values(101, 'Roger', 'Federer')")
    query.exec_("insert into sportsmen values(102, 'Christiano', 'Ronaldo')")
    query.exec_("insert into sportsmen values(103, 'Ussain', 'Bolt')")
    query.exec_("insert into sportsmen values(104, 'Sachin', 'Tendulkar')")
    query.exec_("insert into sportsmen values(105, 'Saina', 'Nehwal')")
    return True


if __name__ == '__main__':
    import sys

    app = QApplication(sys.argv)
    createDB()