How to call a function from a different class in Python

Question

I have the following outline of a Python program (using PyQt4):

class Polygon( QtGui.QGraphicsItem ):

    def __init__(self):
        super(Polygon, self).__init__()

    def addpoint( self, point ):
        if last_point: 
            # trying to add auto-save here

class MainWidget(QtGui.QWidget):

    openFileName = ""
    list_of_polygons = []

    def __init__(self):
        super(MainWidget, self).__init__()

    def openFile( self ):
        call dialog
        self.openFileName = ...

    def saveFile( self ):
        # needs to access a couple something with self.variables, like self.openFileName


def main():

    app = QtGui.QApplication(sys.argv)
    ex = MainWidget()
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()

Functionality is an image viewer where I'm creating polygons to tag object. I'd like to call an auto-save once a polygon has been created.

So for saving a polygon I need to call it from the saveFile function MainWidget class. My problem is that the saving functionality is implemented in the MainWidget class, and I don't know how to access them from inside the Polygon class.

What would be the best idea to do this? Should I make saveFile global? If yes, then how do I access the self. variables of the MainWidget?

Seriously, you're thinking of having to app do a saveFile() after every addpoint()? Sounds slow, especially if the points are being created interactively by a user... — martineau
– martineau, Commented Oct 26, 2012 at 19:54
Each polygon has about 4-10 points. I'm only saving once the polygon is finished. Just not included it in the code. — hyperknot
– hyperknot, Commented Oct 26, 2012 at 20:05

Amber · Accepted Answer · 2012-10-26 18:31:13Z

2

You probably need to pass the widget object to the Polygon when you create it so that it knows what its "parent" widget object is:

class Polygon( QtGui.QGraphicsItem ):

    def __init__(self, parent):
        self.parent = parent
        # ...

(and then foo = Polygon(your_widget) when you create it).

Then you can just call self.parent.saveFile(...) or whatnot.

answered Oct 26, 2012 at 18:31

Amber

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