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I'm using PyQt and Matplotlib libraries to create an application. I've created a sub-class of my QMainWindow and I do not know how to connect the method of the new class to the methods in the first class.

At first, I created a QPushButton in the QMainWindow like this:

class A(QMainWindow):
  def __init__(self):
    QMainWindow.__init__(self)

    self.mainWidget = QWidget()
    self.setCentralWidget(self.mainWidget)

    layout = QVBoxLayout()
    self.mainWidget.setLayout(layout)

    self.figure_canvas = FigureCanvas(Figure(facecolor="lightblue"))
    layout.addWidget(self.figure_canvas, 10)

    self.axes = self.figure_canvas.figure.add_subplot(111)

    #Here is the first button creatd and added to the navigation toolbar
    #using addWidget
    self.btn_selection_tool = QPushButton(QIcon("select.png"), "")
    self.navigation_toolbar.addWidget(self.btn_selection_tool)

    #And here is how i connected this button to two methods
    self.connect(self.btn_selection_tool, SIGNAL("clicked()"), self.method1)
    self.connect(self.btn_selection_tool, SIGNAL("clicked()"), self.method2)

But now, I had to create a new class (class B) and I need to connect a method from this one to the methods called before by the QPushButton in class A. But, in this case, I do not have a button to do it. I just need to "trigger" this methods in class A , by a method in class B.

My problem is that I can not call the methods in class A (self.method1 and self.method2)the same way that I did when I created the QPushbutton. This is before creating the subclass.

I've tried doing: 

def method_in_B_class(self):
  self.a  = A()
  self.a.method1()
  self.a.method2()

How can I do this? Hope you can help me.

------ EDIT -----

These are the two methods:

def method1(self):
    self.figure_canvas.setCursor(Qt.IBeamCursor)
    self.selection_mode = None
    #self.selectionmode is a variable that I change when method1 is called
    #and I can go through the "if" in method2

def method2(self):
    #I define some conditions with another variables
    if len(self.axes.lines) >= 1 and self.selection_mode == None and A.send_msg == None:

        self.cid_press = self.figure_canvas.mpl_connect("button_press_event", self.method3)
        self.cid_release = self.figure_canvas.mpl_connect("button_release_event", self.method4)

    elif self.selection_mode == "disable":
        self.disconnect(self)

So, when they are called using:

def method_in_B_class(self):
  self.a  = A()
  self.a.method1()
  self.a.method2()

they are instantiated, but then they are "finished" we might say. This is that the QtCursor does not change, and the method3 and method4 are not called.

Pablo Flores
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  • Should probably pass through `parent=parent`. – tacaswell May 29 '16 at 20:13
  • `NavigationToolbar2.__init__(self, figure_canvas, parent= None)` -> `NavigationToolbar2.__init__(self, figure_canvas, parent=parent)` but I think that is unrelated to your problem. – tacaswell May 29 '16 at 20:27
  • and I would look at the code `matplotlib.backends.backend_qt5.py` to see how the toolbar gets built. Is the problem that 'bye' is not being called or something else? – tacaswell May 29 '16 at 20:29
  • I've tried that, an it is not the problem. Sorry, I did not understand. The problem is that when the `method1` and `method2` are called, they do not "act" like when I call them using the `QPushButton`. – Pablo Flores May 29 '16 at 20:35
  • Probably because you are calling them directly, not invoking them via slots/signals. You are also creating a new instance of `A`. You probably should have your custom toolbar have a signal that you can then connect to the slot on `A` and emit on in `bye`. – tacaswell May 29 '16 at 20:39
  • I edited the question to explain myself better. Hope this helps – Pablo Flores May 29 '16 at 20:46
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    Everytime you call `bye` you are creating a new instance of `A` (your whole window) and operating on _that_ instance. – tacaswell May 29 '16 at 20:48
  • What should I do then? – Pablo Flores May 29 '16 at 21:03
  • Either use signals/slots to connect out or pass a ref to A into your toolbar (I strongly suspect that it comes in as parent) – tacaswell May 29 '16 at 21:31

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