Type stubs for PySide2 (and soon PySide6)

The most accurate type stubs for PySide! They have been tested using mypy on a code base with many thousands of lines of PySide code.

Comparison to other PySide stubs

I tried a number of projects before deciding to create my own. Here's my super-biased assessment:

Stub Project	Technique	Rating
Official stubs	Uses PySide's generate_pyi stub generator	abysmal
PySide2-Stubs-Gen	Uses a modified version of generate_pyi	marginal
PySide2-stubs	Reprocesses official stubs using libcst	better
types-PySide2	Uses mypy's stubgen	best

PySide2-stubs is pretty good, but it still produced hundreds of errors in our code base. I considered contributing new features to that project, but the approach of using an AST/CST parser to modify an upstream set of bad official stubs to make them good is convoluted and prone to errors from upstream changes. This project uses mypy's official stubgen tool to directly generate stubs, with a set of corrections applied.

Features and fixes

General fixes

• Fixed an issue where methods/attributes were not detected, due to presence of QObject.__getattr__()
• Added all signals and made new-style signal patterns work
  • e.g. myobject.mysignal.connect(func) and myobject.mysignal[type].connect(func)
  • Fixed slot arg of SignalInstance.connect() to be typing.Callable instead of object
  • Fixed Signal.emit()
  • Fixed Signal.connect() return value to bool instead of None
  • Fixed Object.disconnect()
• Added all methods to flag classes: __or__, __xor__, ...

Rule-based fixes

• When instantiating subclasses of QObject it is possible to pass the values of properties and signals as **kwargs to __init__. The stubs have been fix to include these args on all relevant __init__ methods.
• Qt/PySide has special "flag" enumerator classes that work as pairs: one represents a single flag value, while the other represents multiple combined. The stubs have been fix to allow either type of flag -- single or multiple -- anywhere that one of the would have been accepted, which is the correct behavior (technically typing.SupportsInt is the most correct, but using this would undermine the type enforcement provided by the stubs).
• Removed redundant overlapping overloads, so that satisfying mypy/liskov on subclassed methods is easier
• For methods that implement both classmethod and instancemethod overloads, the classmethod overloads have been removed. Unfortunately, mypy disallows mixing these and does not correctly analyze them.
• Corrected all arguments typed as typing.Sequence to be typing.Iterable. Tests so far have indicated that this is true as a general rule.
• Added sub-types to Iterable annotations, e.g. Iterable[str], Iterable[int], etc
• Replaced object with typing.Any in return types. e.g.:
  • QSettings.value() -> Any
  • QModelIndex.internalPointer() -> Any
  • QPersistentModelIndex.internalPointer() -> Any

Specific fixes

• Certain argument types implicitly accept alternative types for brevity. Below are the known fixes so far (Note that I've debated not including these, since one of the advantages of static typing is it gives you the confidence to be explicit rather than ambiguous. I could introduce a strict mode in the future that would disable these):
  • QKeySequence: str
  • QColor: Qt.GlobalColor and int
  • QBrush: QLinearGradient and QColor (and by extension Qt.GlobalColor)
  • QCursor: Qt.CursorShape
  • QEasingCurve: QEasingCurve.Type
• Corrected numerous annotations from bytes/QByteArray to str:
  • QObject.setProperty()
  • QObject.property()
  • QState.assignProperty()
  • QCoreApplication.translate()
  • format args on all methods
• Fixed QTreeWidgetItemIterator.__iter__() to return Iterator[QTreeWidgetItemIterator]
• Added missing QDialog.exec() method
• Fixed numerous methods which accept None:
  • QPainter.drawText(..., br)
  • QPainter.drawPolygon(..., arg__2)
  • QProgressDialog.setCancelButton(button)
  • *.setModel(model)
  • QLabel.setPixmap(arg__1)
• Fixed numerous arguments that accept QModelIndex which were typed as int
• Fixed return type for QApplication.instance() and QGuiApplication.instance()
• Fixed return type for QObject.findChild() and QObject.findChildren()
• Fixed support for initializing QDate from datetime.date
• Fixed support for initializing QDateTime from datetime.datetime
• Fixed QByteArray.__iter__() to return Iterator[bytes]
• Fixed support for bytes(QByteArray(b'foo'))
• Added support for all QSize and QSizeF operations
• Added support for all QPolygon operations
• Fixed QTextEdit.setFontWeight() to accept QFont.Weight
• Fixed return type for qVersion()
• Add QSpacerItem.__init__/changeSize overloads that use alternate names: hData->hPolicy, vData->vPolicy

Licensing

As a derived work from PySide2, the stubs are delivered under the LGPL v2.1 . See file LICENSE for more details.

Installation

Install the latest stub packages from pypi:

$ pip install types-PySide2

This will add the PySide2-stubs and shiboken2-stubs packages into your site-packages directory.
Yes, the name of the pypi package is types-PySide2 but the python package it installs is PySide2-stubs.
It's confusing, but PEP 561 requires that the installed package name is of the form $PACKAGE-stubs, so all of us PySide stub developers are installing a package with the same name.

Note, you may need to uninstall other PySide2 stubs first:

$ pip uninstall PySide2-stubs

Help improve the stubs

If you notice incorrect or missing typing information (i.e. mypy reports errors even though your code is correct), please report it or make a PR to fix it.

Testing

python3 -m venv .venv
. .venv/bin/activate
tox

TODO

• Build PySide6 stubs
• Merge overloads where a Union would do instead of multiple overloads
• Add type enforcement for signal types, to protect against incorrect callables provided to connect()