[PyQt] Properties in PyQt5

[Glenn Ramsey]

Hi,

I have a dialog that has been created in Qt Designer and I would like to
be able to set a red border on a QLineEdit based on its contents (or lack thereof).

Below is what I have tried, based on the PyQt4 version in Mark Summerfield's
book "Rapid GUI programming with Python and Qt", but it doesn't work.

What have I done wrong here?

Glenn

ui = Ui_MyDialog()
ui.setupUi(self)

...

invalidStyle = """
QLineEdit[invalid="true"] {
    border: 2px solid red;
}
"""

ui.myLineEdit.setStyleSheet(invalidStyle)

print ui.myLineEdit.property("invalid")
# prints None

ui.myLineEdit.setProperty("invalid", QVariant(True))

print ui.myLineEdit.property("invalid")
# prints True

# expected my QLineEdit to have a red border now, but it doesn't change its
appearance.