Saving class data containing pyqt objects

Question

I'm building a PyQt app and I'm quite beginner with python. Let's say I store an obj item in a defined class:

class Item (self):
    def __init__(self, item_nbr, crop_pixmap, originepoint, designation):
        self.item_nbr = item_nbr            # integer
        self.crop_pixmap = crop_pixmap      # QPixmap
        self.origin_point = originpoint     # QPoint
        self.designation = designation      # str

Then I work through a GUI perform other operation and create a list of Items. How can I save this list so that I can open it later ? pickle does not work with QPixmap and I'd like to save a single.

Answer 1

You can use QSettings to save all your application data. It will automatically convert data types like QPixmap, QPoint, QColor, etc. By default, the settings are saved in a platform-independant way, but you can also save to a custom location if you want.

Here is how you could read/write your Item class:

def settings(self):
    # use a custom location
    return QtCore.QSettings('app.conf', QtCore.QSettings.IniFormat)

def readSettings(self):
    self.items = []
    settings = self.settings()
    for index in range(settings.beginReadArray('items')):
        settings.setArrayIndex(index)
        self.items.append(Item(
            settings.value('number', -1, int),
            settings.value('pixmap', None, QtGui.QPixmap),
            settings.value('point', None, QtCore.QPoint),
            settings.value('designation', '', str),
            ))

def writeSettings(self):
    settings = self.settings()
    settings.beginWriteArray('items')
    for index, item in enumerate(self.items):
        settings.setArrayIndex(index)
        settings.setValue('number', item.item_nbr)
        settings.setValue('pixmap', item.crop_pixmap)
        settings.setValue('point', item.origin_point)
        settings.setValue('designation', item.designation)
    settings.endArray()

The PyQt version of QSettings.value() allows you to specify both a default value and the expected type of the value.