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)?

About your specific issue: you have to add self as an argument to test_print (i.e. test_print(self)). — ArMoraer, Jan 25 '17 at 10:38
It did not work. This works however (see initial question). How can I call a function that is not inside the run method? — geogrow, Jan 25 '17 at 11:04
The method provided by @ArMoraer worked for me. Did you receive any errors in the Python Console when you tried using test_print(self)? — Joseph, Jan 25 '17 at 11:09
Maybe I am missing something very obvious here but I get this NameError: global name 'test_print' is not defined — geogrow, Jan 25 '17 at 11:23
Is this your entire plugin? Just one file with a "run" function in it? — Spacedman, Jan 25 '17 at 11:26
@Spacedman No, I used Plugin builder for the structure. So it contain all the default files it creates. — geogrow, Jan 25 '17 at 11:28

score 1 · Accepted Answer · edited Apr 13 '17 at 12:34

Try moving the line:
```
self.dlg.pushButton.clicked.connect(self.test_print)
```
to the initGui(self) function instead of in the run(self) function.

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

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!'

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?

Great now it works! Really appreciate it, a good simple starting point. I created a new plugin from the Plugin builder and both @Joseph and @ArMoraer works. I just found that i had moved self.dlg = TestPluginDialog() from the add_action method to the init (followed an example before) that made it not functioning properly. Thanks for all your help! — geogrow, Jan 25 '17 at 12:18
@geogrow - Most welcome and nice one! Glad you got it working =) — Joseph, Jan 25 '17 at 12:21

QGIS first simple plugin

1 Answers1