QGIS first simple plugin

Question

I am trying to learn how to develop QGIS plugins but I struggle to get going by some simple principles.

As a test I am just trying to connect a function to a button. So when pressed the function run. Where to put the function and connections are not obvious to me.

This example give me an error message TypeError: test_print() takes no arguments (2 given) I cannot see how this give test_print 2 arguments?

def run(self):

    # Run test_print method when pushButton is clicked
    self.dlg.pushButton.clicked.connect(self.test_print)

    # show the dialog
    self.dlg.show()

def test_print():
    print 'It works!'

Does anyone has any general advice how to wire up buttons and functions properly?

EDIT: Working test example

This worked.

def run(self):

        def test_print():
            QMessageBox.about(None,'test','It works!')

        # Run test_print method when pushButton is clicked
        self.dlg.pushButton.clicked.connect(test_print)

Now, how can i run the test_print method if its not inside def run(self)?

Answer 1

1. Try moving the line:

   self.dlg.pushButton.clicked.connect(self.test_print)
   

   to the initGui(self) function instead of in the run(self) function.

---

2. As @ArMoraer mentioned, put your test_print(self) outside the run(self) function.

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3. Here is the part of the Example.py script I used to test it:

   def initGui(self):
       """Create the menu entries and toolbar icons inside the QGIS GUI."""
       icon_path = ':/plugins/Example/icon.png'
       self.add_action(
           icon_path,
           text=self.tr(u'Example'),
           callback=self.run,
           parent=self.iface.mainWindow())
   
       # Run test_print method when pushButton is clicked
       self.dlg.pushButton.clicked.connect(self.test_print)
   
   def run(self):        
       """Run method that performs all the real work"""
       # show the dialog
       self.dlg.show()
       result = self.dlg.exec_()
       if result:
           pass
   
   def test_print(self):
       print 'It works!'
   

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You can also take a look at the following post which describes the fundamental parts of a QGIS plugin:

What is the purpose of some functions and files in QGIS Python plugins?