[GIS] Getting QGIS installation path in PyQGIS

pyqgis

Is there any way to get the QGIS installation path programmatically?

I'm working on something similar to plugin installer and it would be great to have it.

Best Answer

In my GNU/Linux Debian, at the Python Console of QGIS, I type:

>>>print QgsApplication.showSettings()

and I got:

Application state:
QGIS_PREFIX_PATH env var:       
Prefix:     /usr
Plugin Path:        /usr/lib/qgis/plugins
Package Data Path:  /usr/share/qgis
Active Theme Name:  default
Active Theme Path:  /home/zeito/.qgis2///themes/default/icons/
Default Theme Path: :/images/themes/default/
SVG Search Paths:   /usr/share/qgis/svg/
        /home/zeito/.qgis2//svg/
User DB Path:   /usr/share/qgis/resources/qgis.db
Auth DB Path:   /home/zeito/.qgis2//qgis-auth.db

You can also assign print command to a variable for using it programmatically after some string manipulations and by using regular expressions python module (re). For example:

import re

def getPattern(keyword, L):

    list = [ item for item in L if re.search(keyword, item) is not None ]

    return list 

qgis_paths = QgsApplication.showSettings()
qgis_paths = qgis_paths.split('\n')

print getPattern('Package', qgis_paths)

that produces:

[u'Package Data Path:\t/usr/share/qgis']

In this case, it was individualized the 'Package Data Path'.

Editing Note:

I found out that it could be easier with these commands:

print QgsApplication.pluginPath() #location of core plugins
print QgsApplication.prefixPath() #location where QGIS is installed
print QgsApplication.qgisSettingsDirPath() #location of user settings
print QgsApplication.iconsPath() #location of icons used in QGIS

where it's produced:

/usr/lib/qgis/plugins
/usr
/home/zeito/.qgis2//
/usr/share/qgis/images/icons/

Related Solutions

[GIS] QGIS plugin: Problems importing resources (resources_rc) file – plugin doesn’t load – PATH problems

This problem is caused by uic not working properly. I am not sure exactly why but I can show the symptoms and a workaround.

The initial plugin .ui file has an empty resources element:

<resources/>

When you edit the resources for the plugin in QtDesigner this changes to:

<resources>
  <include location="resources.qrc"/>
</resources>

This is the source of the problem. If you change the .qrc file in that include tag to resourcesXXX.qrc the error will change to No module named resourcesXXX_rc.

Note: the following is based upon a plugin build with 'test' entered into all fields of the QGIS plugin builder.

In the test_dialog.py file the following lines compile the .ui file:

FORM_CLASS, _ = uic.loadUiType(os.path.join(
    os.path.dirname(__file__), 'test_dialog_base.ui'))

This is where the error is occurring.

Edit your .ui file to change back to <resources/> and the problem is resolved. Until you edit your dialog in QtDesigner again. You must make this edit to the .ui file after each time you edit your dialog.

The solution to this is to change your plugin to work like earlier versions of the plugin worked. This involves replacing the uic call and the class lines in the _dialog.py file. Replace these lines:

FORM_CLASS, _ = uic.loadUiType(os.path.join(
    os.path.dirname(__file__), 'test_dialog_base.ui'))

class testDialog(QtGui.QDialog, FORM_CLASS):

with:

from test_dialog_base import Ui_testDialogBase

class testDialog(QDockWidget, Ui_testDialogBase):

You will now have to run

pyuic4 -x test_dialog_base.ui > test_dialog_base.py

when you first create your plugin and each time you edit your plugin dialog with QtDesigner. This was the old plugin method.

Whether to edit the .ui file or the run pyuic4 each time is your choice.

[GIS] Getting extent of composer map in PyQGIS

In order to use the result in an expression, a custom python expression is necessary. Here's the code I've come up with:

from qgis.core import *
from qgis.gui import *
from qgis.utils import iface

@qgsfunction(args='auto', group='Custom')
def getScale(composerName, mapName, feature, parent):
    # dictionary to store QgsComposerView.composition() items by name
    compDict = {}
    for comp in iface.activeComposers():
        # workaround to get name: read it from window title
        compDict[comp.composerWindow().windowTitle()] = comp.composition()
    mapScale = 0 # default to be returned if scale not found
    if composerName in compDict:
        mapItem = compDict[composerName].getComposerItemById(mapName)
        if mapItem:
            mapScale = mapItem.scale()
    return mapScale

The first challenge is getting a composer by name. Create a dictionary to hold the composers, then iterate over the activeComposers() list, storing them by name in the dictionary.

Next, if the composer name we're looking for is in the list, get the requested map and it's extent. Return either it or 0 to denote not found.

This works great with an atlas controlled map:

In this case the expression used for the label is:

'scale' || getScale('Composer 1', 'Map 0')

Best Answer

Related Solutions

[GIS] QGIS plugin: Problems importing resources (resources_rc) file – plugin doesn’t load – PATH problems

[GIS] Getting extent of composer map in PyQGIS

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