Source: python – Unable to load QMYSQL Driver on PySide2 – Stack Overflow
The binaries used by Qt are the same ones used by PyQt5/PySide2 since they use the same base code so you will have to compile the plugins.
In this case, to compile the mysql plugin you must follow the official manual, which in summary is:
- Install the dependencies, in this case the mysql-connector-c
- Install Qt of the same version with which pyqt5/pyside2 was compiled and development tools such as MSVC on windows, build-essentials on Ubuntu, XCode on MacOS, etc.
- Download the source code, in this case the qtbase repository.
- Compile the plugin.
To find out the version of Qt with the version that the library was compiled with, the following can be used:
- PyQt5
python -c "from PyQt5.QtCore import QT_VERSION_STR; print('Qt version', QT_VERSION_STR)"
- PySide2
python -c "from PySide2.QtCore import qVersion; print('Qt version', qVersion())"
The above generates libqsqlmysql.so, qsqlmysql.dll or libqsqlmysql.dylib depending on the OS. That file must be pasted in the path:
- PyQt5:
python -c "import os; from PyQt5.QtCore import QLibraryInfo; print('QT_SQL_DRIVER_PATH', os.path.join(QLibraryInfo.location(QLibraryInfo.PrefixPath), 'plugins', 'sqldrivers'))"
- PySide2:
python -c "import os; from PySide2.QtCore import QLibraryInfo; print('QT_SQL_DRIVER_PATH', os.path.join(QLibraryInfo.location(QLibraryInfo.PrefixPath), 'plugins', 'sqldrivers'))"
To cover all the cases I have created a Github Actions that generates the binaries:
name: generate_mysql_plugin
on: [push]
jobs:
ci:
name: ${{ matrix.os.name }} Qt-${{ matrix.qt.qt_version }}
runs-on: ${{ matrix.os.runs-on }}
strategy:
fail-fast: false
matrix:
os:
- name: Windows
extension: "dll"
runs-on: windows-2019
- name: Linux
extension: "so"
runs-on: ubuntu-20.04
- name: MacOS
extension: "dylib"
runs-on: macos-10.15
qt:
- name: 5.15
qt_version: 5.15.0
steps:
- name: Checkout
uses: actions/checkout@v1
- name: Install Qt
uses: jurplel/install-qt-action@v2
with:
version: ${{ matrix.qt.qt_version }}
dir: ${{ github.workspace }}/qt/
- name: clone qtbase
run: git clone -b ${{ matrix.qt.qt_version }} https://code.qt.io/qt/qtbase.git
- name: Compile mysql plugin on Windows
if: matrix.os.name == 'Windows'
shell: cmd
run: |
choco install wget
wget https://downloads.mysql.com/archives/get/p/19/file/mysql-connector-c-6.1.11-winx64.zip
unzip mysql-connector-c-6.1.11-winx64.zip
copy /y "mysql-connector-c-6.1.11-winx64\lib\libmysql.dll" .
call "C:/Program Files (x86)/Microsoft Visual Studio/2019/Enterprise/VC/Auxiliary/Build/vcvars64.bat"
cd qtbase/src/plugins/sqldrivers
qmake -- MYSQL_INCDIR="${{ github.workspace }}\mysql-connector-c-6.1.11-winx64\include" MYSQL_LIBDIR="${{ github.workspace }}\mysql-connector-c-6.1.11-winx64\lib"
nmake sub-mysql
nmake install
- name: Compile mysql plugin on Linux
if: matrix.os.name == 'Linux'
run: |
wget https://downloads.mysql.com/archives/get/p/19/file/mysql-connector-c-6.1.11-linux-glibc2.12-x86_64.tar.gz
tar zxvf mysql-connector-c-6.1.11-linux-glibc2.12-x86_64.tar.gz
sudo cp mysql-connector-c-6.1.11-linux-glibc2.12-x86_64/lib/*.so /usr/lib/x86_64-linux-gnu
sudo apt-get install freetds-dev
cd qtbase/src/plugins/sqldrivers
qmake
cd mysql
qmake
make
make install
- name: Compile mysql plugin on MacOS
if: matrix.os.name == 'MacOs'
run: |
brew install wget
wget https://cdn.mysql.com/archives/mysql-connector-c/mysql-connector-c-6.1.11-macos10.12-x86_64.tar.gz
tar zxvf mysql-connector-c-6.1.11-macos10.12-x86_64.tar.gz
sudo cp mysql-connector-c-6.1.11-macos10.12-x86_64/lib/libmysqlclient.dylib mysql-connector-c-6.1.11-macos10.12-x86_64/lib/libmysqlclient_r.dylib
sudo cp mysql-connector-c-6.1.11-macos10.12-x86_64/lib/libmysqlclient.18.dylib mysql-connector-c-6.1.11-macos10.12-x86_64/lib/libmysqlclient_r.18.dylib
sudo cp mysql-connector-c-6.1.11-macos10.12-x86_64/lib/*.dylib /usr/local/lib
cd qtbase/src/plugins/sqldrivers
qmake -- MYSQL_PREFIX="${{ github.workspace }}/mysql-connector-c-6.1.11-macos10.12-x86_64"
make sub-mysql
cd mysql
make install
- name: upload
uses: actions/upload-artifact@v2
with:
path: qtbase/src/plugins/sqldrivers/plugins/sqldrivers/*qsqlmysql.${{ matrix.os.extension }}
name: mysqlplugin-${{ matrix.os.name }}-Qt${{ matrix.qt.name }}
The previous code generates the plugin that you can find here.
In the specific case of Ubuntu it can be reduced to:
- Copy the libqsqlmysql.so file to QT_SQL_DRIVER_PATH.
- Execute
sudo apt install libmysqlclient-dev
In the specific case of Windows it can be reduced to:
- Copy the qsqlmysql.dll file to QT_SQL_DRIVER_PATH.
- Download the mysql-connector-c for windows and copy the libmysql.dll next to your script.
P.S. almost half of this info is officially published at https://doc.qt.io/qt-6/deployment-plugins.html
I use PySide6 on Windows 10 and %QT_SQL_DRIVER_PATH%
does not work for me. What works for PySide6 is the %QT_PLUGIN_PATH%
environment variable.
Let’s assume that you have built (or downloaded) a SQL driver for Qt platform into C:\projects\my-project-1\qt-plugins\sqldrivers
, so that there is qsqlmysql.dll
there.
CASE #1: you execute QSqlDatabase.addDatabase("QMYSQL")
, but you get the following error:
QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QODBC QPSQL
It means that qsqlmysql.dll
(a plugin for Qt platform) was not found.
The fix is to define the environment variable %QT_PLUGIN_PATH%
and put qsqlmysql.dll
into %QT_PLUGIN_PATH%/sqldrivers/
. You can even do it in your Python script before invocation of QSqlDatabase.addDatabase
:
os.environ['QT_PLUGIN_PATH'] = r'C:\projects\my-project-1\qt-plugins'
Note, qsqlmysql.dll
must be a release version built using MSVC (64-bit since it is year 2022), not MinGW. Debug version fails by some reason in my experience.
If you don’t want to define the %QT_PLUGIN_PATH%
environment variable, an alternative fix is to copy qsqlmysql.dll
into one of these directories: <python-install-dir>/sqldrivers/
or <python-install-dir>/lib/site-packages/PySide6/plugins/sqldrivers/
.
Another alternative is to use QCoreApplication.addLibraryPath
like this:
app = QCoreApplication(sys.argv)
app.addLibraryPath(r'C:\projects\my-project-1\qt-plugins')
And yet another alternative is to create <python-install-dir>\qt.conf
or <python-install-dir>\qt6.conf
with following content:
[Paths]
Prefix=C:/projects/my-project-1
Plugins=qt-plugins
or even so:
[Paths]
Plugins=C:/projects/my-project-1/qt-plugins
N.B. qt6.conf is ignored if qt.conf
doesn’t exist. If you use qt6.conf
, you must create an empty qt.conf
at least.
CASE #2: you execute QSqlDatabase.addDatabase("QMYSQL")
, but you get the following error:
QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QMARIADB QMYSQL QSQLITE QODBC QPSQL
It means that qsqlmysql.dll
was found, but its dependencies were not. The qsqlmysql.dll
additionally requires 3 DLLs: libmysql.dll
, libcrypto-1_1-x64.dll
, libssl-1_1-x64.dll
. These DLLs must be located in %PATH%
or in current directory.
N.B. if you place the DLLs near your python script, this won’t work if current working directory is different from scripts’s location. But you can modify %PATH%
even in your Python script. For example, if you copied said DLLs into deps
sub-directory of your project:
os.environ["PATH"] += os.pathsep + os.path.join(os.path.dirname(__file__), 'deps')
Another possible issues might be:
- architecture mismatch (some DLLs are 64-bit, while others are 32-bit).
- binary incompatibility – e.g. if “sqldrivers/qsqlmysql.dll” is built with MinGW or it’s a debug version downloaded from https://github.com/thecodemonkey86/
Define the environment variable: set QT_DEBUG_PLUGINS=1
– this might help to troubleshoot such issues.