Blog

The “QPSQL driver not loaded” error typically occurs when the PostgreSQL driver for Qt is not properly installed or configured. Here are some steps to resolve this issue on macOS:

1. Install PostgreSQL:
   • Ensure that PostgreSQL is installed on your system. You can install it using Homebrew:

     brew install postgresql
     

2. Install Psycopg2:
   • Make sure you have the psycopg2 library installed, which is a PostgreSQL adapter for Python:

     pip install psycopg2-binary
     

3. Set Environment Variables:
   • Ensure that the PostgreSQL binaries are in your PATH. You can add the following lines to your .bash_profile or .zshrc file:

     export PATH="/usr/local/opt/postgresql/bin:$PATH"
     export DYLD_LIBRARY_PATH="/usr/local/opt/postgresql/lib:$DYLD_LIBRARY_PATH"
     

4. Check Available Drivers:
   • Verify that the QPSQL driver is available in your Qt installation. You can run the following Python script to check:
     Python

     from PySide6.QtSql import QSqlDatabase
     from PySide6.QtWidgets import QApplication
     
     app = QApplication([])
     db = QSqlDatabase("QPSQL")
     print("Available drivers:", db.drivers())
     if not db.open():
         print("Unable to connect.")
         print("Last error:", db.lastError().text())
     else:
         print("Connection to the database successful")
     

     AI-generated code. Review and use carefully. More info on FAQ.
5. Build the QPSQL Plugin:
   • If the driver is not available, you may need to build the QPSQL plugin manually. Here are the steps:

     cd $QTDIR/qtbase/src/plugins/sqldrivers
     qmake -- PSQL_INCDIR=/usr/local/opt/postgresql/include PSQL_LIBDIR=/usr/local/opt/postgresql/lib
     make sub-psql
     

6. Verify Plugin Location:
   • Ensure that the qsqlpsql.dylib file is located in the correct directory. It should be in the sqldrivers directory of your Qt installation.

By following these steps, you should be able to resolve the “QPSQL driver not loaded” error and successfully connect to a PostgreSQL database using Qt and Python on macOS¹².

If you encounter any issues or need further assistance, feel free to ask! 😊