The QLineEdit has a outer border line with the default style, can't remove it.

When the QLineEdit got focus, it will show a outer border line at the default style, when change the application style to "Fusion", the line will gone.

self.lineEdit = QLineEdit(self)
self.lineEdit.setGeometry(QRect(20, 20, 100, 30))
self.lineEdit.setStyleSheet("QLineEdit:focus

");
self.lineEdit.setFrame(False)

stackoverflow link