Qt for Python 注意事项 ¶

__hash__() function return value ¶

The hash value returned for the classes PySide2.QtCore.QDate , PySide2.QtCore.QDateTime , PySide2.QtCore.QTime , PySide2.QtCore.QUrl will be based on their string representations, thus objects with the same value will produce the same hash.

QString ¶

Methods and functions that change the contents of a QString argument were modified to receive an immutable Python Unicode (or str) and return another Python Unicode/str as the modified string.

The following methods had their return types modified this way:

Classes: QAbstractSpinBox, QDateTimeEdit, QDoubleSpinBox, QSpinBox, QValidator

• fixup(string): string

• validate(string, int): [QValidator.State, string, int]

Classes: QDoubleValidator, QIntValidator, QRegExpValidator

• validate(string, int): [QValidator.State, string, int]

Class: QClipboard

• text(string, QClipboard.Mode mode=QClipboard.Clipboard): [string, string]

Class: QFileDialog

Instead of getOpenFileNameAndFilter() , getOpenFileNamesAndFilter() and getSaveFileNameAndFilter() like PyQt does, PySide has modified the original methods to return a tuple.

• getOpenFileName(QWidget parent=None, str caption=None, str dir=None, str filter=None, QFileDialog.Options options=0): [string, filter]

• getOpenFileNames(QWidget parent=None, str caption=None, str dir=None, str filter=None, QFileDialog.Options options=0): [list(string), filter]

• getSaveFileName(QWidget parent=None, str caption=None, str dir=None, str filter=None, QFileDialog.Options options=0): [string, filter]

Class: QWebPage

• javaScriptPrompt(QWebFrame, string, string): [bool, string]

Classes: QFontMetrics and QFontMetricsF

They had two new methods added. Both take a string of one character and convert to a QChar (to call the C++ counterpart):

• widthChar(string)

• boundingRectChar(string)

QTextStream ¶

Inside this class some renames were applied to avoid clashes with native Python functions. They are: bin_() , hex_() and oct_() . The only modification was the addition of the ‘_’ character.

QVariant ¶

As QVariant was removed, any function expecting it can receive any Python object ( None is an invalid QVariant ). The same rule is valid when returning something: the returned QVariant will be converted to its original Python object type.

When a method expects a QVariant::Type the programmer can use a string (the type name) or the type itself.

qApp “macro” ¶

The C++ API of QtWidgets provides a macro called qApp that roughly expands to QtWidgets::QApplication->instance() .

In PySide, we tried to create a macro-like experience. For that, the qApp variable was implemented as a normal variable that lives in the builtins. After importing PySide2 , you can immediately use qApp .

As a useful shortcut for the action “create an application if it was not created”, we recommend:

qApp or QtWidgets.QApplication()
										

or if you want to check if there is one, simply use the truth value:

if qApp:
    # do something if an application was created
    pass
										

Comparing to None is also possible, but slightly over-specified.

qApp.shutdown()