> ## Documentation Index
> Fetch the complete documentation index at: https://anki.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Qt and PyQt

As mentioned in the overview, Anki uses PyQt for a lot of its UI, and the Qt
documentation and [PyQt
documentation](https://www.riverbankcomputing.com/static/Docs/PyQt6/sip-classes.html)
are invaluable for learning how to display different GUI widgets.

## Qt Versions

From Anki 2.1.50, separate builds are provided for PyQt5 and PyQt6. Generally
speaking, if you write code that works in Qt6, and make sure to import any Qt
classes from aqt.qt instead of directly from PyQt6, your code should also work
in Qt5.

## Designer Files

Parts of Anki's UI are defined in .ui files, located in `qt/aqt/forms`. Anki's
build process converts them into .py files. If you wish to build your add-on's
UI in a similar way, you will need to install Python, and install a program
called Qt Designer (Designer.app on macOS). On Linux, it may be available in
your distro's packages; on Windows and Mac, you'll need to install it as part of
a [Qt install](https://download.qt.io/). Once installed, you will need to use a
program provided in the pyqt6 pip package to compile the .ui files.

Generated Python files for PyQt6 won't work with PyQt5 and vice versa, so if you
wish to support both versions, you will need to build the .ui files twice, once
with pyuic5, and once with pyuic6.

## Garbage Collection

One particular thing to bear in mind is that objects are garbage
collected in Python, so if you do something like:

```python theme={null}
def myfunc():
    widget = QWidget()
    widget.show()
```

…​then the widget will disappear as soon as the function exits. To
prevent this, assign top level widgets to an existing object, like:

```python theme={null}
def myfunc():
    mw.myWidget = widget = QWidget()
    widget.show()
```

This is often not required when you create a Qt object and give it an
existing object as the parent, as the parent will keep a reference to
the object.