1

I am trying to create a basic custom QGIS plugin - all it will do is load a dataset from a list into the current project.

I keep getting the above error and can't figure out what's causing it.

I can't find (the probably small error in the code). The zip with the plugin is here

The detailed error is below

Couldn't load plugin 'add_layer' due to an error when calling its classFactory() method 

SyntaxError: invalid syntax 
Traceback (most recent call last):
  File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 335, in startPlugin
    plugins[packageName] = package.classFactory(iface)
  File "C:/Users/George/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\add_layer\__init__.py", line 35, in classFactory
    from .add_layer import add_layer
  File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 672, in _import
    mod = _builtin_import(name, globals, locals, fromlist, level)
  File "C:/Users/George/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\add_layer\add_layer.py", line 175
    self.loadVectors()
       ^
SyntaxError: invalid syntax


Python version: 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MSC v.1914 64 bit (AMD64)] 
QGIS version: 3.4.4-Madeira Madeira, 73c31df831 

Python Path:
C:/OSGEO4~1/apps/qgis/./python
C:/Users/George/AppData/Roaming/QGIS/QGIS3\profiles\default/python
C:/Users/George/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins
C:/OSGEO4~1/apps/qgis/./python/plugins
C:\OSGeo4W64\bin\python37.zip
C:\OSGEO4~1\apps\Python37\DLLs
C:\OSGEO4~1\apps\Python37\lib
C:\OSGeo4W64\bin
C:\OSGEO4~1\apps\Python37
C:\OSGEO4~1\apps\Python37\lib\site-packages
C:\OSGEO4~1\apps\Python37\lib\site-packages\win32
C:\OSGEO4~1\apps\Python37\lib\site-packages\win32\lib
C:\OSGEO4~1\apps\Python37\lib\site-packages\Pythonwin
C:/Users/George/AppData/Roaming/QGIS/QGIS3\profiles\default/python

UPDATE: Once I fix the issue with the ( as per the answer below. I get a new error.

Couldn't load plugin 'add_layer' due to an error when calling its initGui() method 

AttributeError: 'add_layer' object has no attribute 'dlg' 
Traceback (most recent call last):
  File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 344, in startPlugin
    plugins[packageName].initGui()
  File "C:/Users/George/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\add_layer\add_layer.py", line 171, in initGui
    self.dlg.tb_inVector.clicked.connect(self.openVector)
AttributeError: 'add_layer' object has no attribute 'dlg'

Code from Python file (same as in zip in link above)

"""
from PyQt5.QtCore import QSettings, QTranslator, qVersion, QCoreApplication
from PyQt5.QtGui import QIcon
from PyQt5.QtWidgets import QAction

# Initialize Qt resources from file resources.py
from .resources import *
# Import the code for the dialog
from .add_layer_dialog import add_layerDialog
import os.path
from qgis.core import *

class add_layer:
    """QGIS Plugin Implementation."""

    def __init__(self, iface):
        """Constructor.

        :param iface: An interface instance that will be passed to this class
            which provides the hook by which you can manipulate the QGIS
            application at run time.
        :type iface: QgsInterface
        """
        # Save reference to the QGIS interface
        self.iface = iface
        # initialize plugin directory
        self.plugin_dir = os.path.dirname(__file__)
        # initialize locale
        locale = QSettings().value('locale/userLocale')[0:2]
        locale_path = os.path.join(
            self.plugin_dir,
            'i18n',
            'add_layer_{}.qm'.format(locale))

        if os.path.exists(locale_path):
            self.translator = QTranslator()
            self.translator.load(locale_path)

            if qVersion() > '4.3.3':
                QCoreApplication.installTranslator(self.translator)

        # Declare instance attributes
        self.actions = []
        self.menu = self.tr(u'&add_layer')

        # Check if plugin was started the first time in current QGIS session
        # Must be set in initGui() to survive plugin reloads
        self.first_start = None

    # noinspection PyMethodMayBeStatic
    def tr(self, message):
        """Get the translation for a string using Qt translation API.

        We implement this ourselves since we do not inherit QObject.

        :param message: String for translation.
        :type message: str, QString

        :returns: Translated version of message.
        :rtype: QString
        """
        # noinspection PyTypeChecker,PyArgumentList,PyCallByClass
        return QCoreApplication.translate('add_layer', message)


    def add_action(
        self,
        icon_path,
        text,
        callback,
        enabled_flag=True,
        add_to_menu=True,
        add_to_toolbar=True,
        status_tip=None,
        whats_this=None,
        parent=None):
        """Add a toolbar icon to the toolbar.

        :param icon_path: Path to the icon for this action. Can be a resource
            path (e.g. ':/plugins/foo/bar.png') or a normal file system path.
        :type icon_path: str

        :param text: Text that should be shown in menu items for this action.
        :type text: str

        :param callback: Function to be called when the action is triggered.
        :type callback: function

        :param enabled_flag: A flag indicating if the action should be enabled
            by default. Defaults to True.
        :type enabled_flag: bool

        :param add_to_menu: Flag indicating whether the action should also
            be added to the menu. Defaults to True.
        :type add_to_menu: bool

        :param add_to_toolbar: Flag indicating whether the action should also
            be added to the toolbar. Defaults to True.
        :type add_to_toolbar: bool

        :param status_tip: Optional text to show in a popup when mouse pointer
            hovers over the action.
        :type status_tip: str

        :param parent: Parent widget for the new action. Defaults None.
        :type parent: QWidget

        :param whats_this: Optional text to show in the status bar when the
            mouse pointer hovers over the action.

        :returns: The action that was created. Note that the action is also
            added to self.actions list.
        :rtype: QAction
        """

        icon = QIcon(icon_path)
        action = QAction(icon, text, parent)
        action.triggered.connect(callback)
        action.setEnabled(enabled_flag)

        if status_tip is not None:
            action.setStatusTip(status_tip)

        if whats_this is not None:
            action.setWhatsThis(whats_this)

        if add_to_toolbar:
            # Adds plugin icon to Plugins toolbar
            self.iface.addToolBarIcon(action)

        if add_to_menu:
            self.iface.addPluginToMenu(
                self.menu,
                action)

        self.actions.append(action)

        return action

    def initGui(self):
        """Create the menu entries and toolbar icons inside the QGIS GUI."""

        icon_path = ':/plugins/add_layer/icon.png'
        self.add_action(
            icon_path,
            text=self.tr(u'add_layer'),
            callback=self.run,
            parent=self.iface.mainWindow())
        self.dlg.tb_inVector.clicked.connect(self.openVector)
        # will be set False in run()
        #self.first_start = True
        #new
        self.loadVectors()

    def loadVectors(self):
        self.dlg.cb_inVector.clear()
        layers= [layer for layer in QgsProject.instance().mapLayers().values()]
        vector_layers = []
        for layer in layers:
            if layer.type() == QgsMapLayer.VectorLayer:
                vector_layers.append(layer.name())
        self.dlg.cb_inVector.addItems(vector_layers)


    def unload(self):
        """Removes the plugin menu item and icon from QGIS GUI."""
        for action in self.actions:
            self.iface.removePluginMenu(
                self.tr(u'&add_layer'),
                action)
            self.iface.removeToolBarIcon(action)


    def run(self):
        """Run method that performs all the real work"""

        # Create the dialog with elements (after translation) and keep reference
        # Only create GUI ONCE in callback, so that it will only load when the plugin is started
        #if self.first_start == True:
        #    self.first_start = False
        #    self.dlg = add_layerDialog()

        # show the dialog
        self.dlg.show()
        self.loadVectors()
        # Run the dialog event loop
        result = self.dlg.exec_()
        # See if OK was pressed
        if result:
            # Do something useful here - delete the line containing pass and
            # substitute with your code.
            pass

OPTIONS TRIED for issue #2 I have tried with self.dlg = add_layerDialog() not commented, I have tried uncommenting the if self.first_start== sections and I have also tried to use the run module from another working plugin {

 def run(self):
        """Run method that performs all the real work"""
        # show the dialog
        self.dlg.show()
        self.loadVectors()
        # Run the dialog event loop
        result = self.dlg.exec_()
        # See if OK was pressed
        if result:
            # Do something useful here - delete the line containing pass and
            # substitute with your code.

}

I keep getting the same error.

2

For your first problem (syntax error):

You got a missing ) the line before your self.loadVectors() call... It's a syntax error as your error's traceback says..

For your second problem (add_layer object has no attribute dlg):

You never create the dlg variable which must instantiate your GUI (class add_layerDialog), please have a look to the code of another plugin as every plugins works on the same basis..

It seems that you're a beginner in python programming. I suggest you to learn a little about OOP to understand what going on when qgis run your plugin code. Basically, the initGui method is called to add button to QGIS main interface. When you click on this button, the run method is called, this is the place where you need to instantiate your dialog in a self.dlg variable. In the initGui method your plugin does not have any dialog associated.

  • Whoops - unfortunately with that changed I am now getting a new error. I will add it to the question. – GeorgeC Feb 2 at 12:10
  • Not sure what you mean? It's in the initGUI and LoadVectors - same as in other plugins. I will add the .py code to the question @YoLecomte – GeorgeC Feb 2 at 13:23
  • 1
    You never define what is self.dlg in your plugin. It must be an instance of your add_layerDialog class. – YoLecomte Feb 2 at 14:07
  • 1
    Btw it is done in the run method of your plugin but commented.... – YoLecomte Feb 2 at 14:14
  • Thanks for your continued support -I have tried this but I still get the same issue. See question for details. – GeorgeC Feb 2 at 22:34

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