PyQGIS – How to Get Source Path of Layer File in PyQGIS

pyqgispythonqgis-plugins

I need the exact source path of layer files as shown by QGIS Layer Properties Information Window:

I know how to retrieve the layer source URI (and using the data provider gives the same result):

    layer = qgis.utils.iface.activeLayer()
    uri = layer.source()
    # uri = layer.dataProvider().dataSourceUri()

Now retrieving the exact layer source path from the URI is not a trivial thing, as it contains information depending on the data provider type.

layer.providerType() == 'delimitedtext' can look something like that:

"file:///home/ubuntu/QGIS/Ciutat%20pr%C3%B2xima%201.0/EDUCACI%C3%93/opendatabcn_llista-equipaments_educacio-csv.csv?encoding=UTF-16&type=csv&maxFields=10000&detectTypes=yes&xField=geo_epgs_25831_x&yField=geo_epgs_25831_y&crs=EPSG:25831&spatialIndex=no&subsetIndex=no&watchFile=no&subset=%20%22secondary_filters_name%22%20%3D%20'Universitat'%20or%20%22secondary_filters_name%22%20%3D%20'Educaci%C3%B3%20secund%C3%A0ria'%20or%20%22secondary_filters_name%22%20%3D%20'Educaci%C3%B3%20prim%C3%A0ria'%20or%20%20%22secondary_filters_name%22%20%3D%20%20%20'Ensenyament%20infantil%20(3-6%20anys)'%20%20%20or%20%20%22secondary_filters_name%22%20%3D%20%20'Ensenyament%20infantil%20(0-3%20anys)'%20or%20%22secondary_filters_name%22%20%3D%20%20%20'Escoles%20Bressol%20municipals'%20"

layer.providerType() == 'ogr' could look like that:

'/vsizip//home/ubuntu/QGIS/Ciutat pròxima 1.0/DEMOGRAFIA/BCN_UNITATS_ADM.zip/0301100100_UNITATS_ADM_POLIGONS.json|layername=0301100100_UNITATS_ADM_POLIGONS|geometrytype=Polygon|subset="CONJ_DESCR"=\'Districtes\''

So it's actually possible to get the layer source path as shown in QGIS, but is there a easy way to do that?

PS: I know this question in a quite similar way has been asked before, but always in a different context or with ambiguous descriptions, like this one (which asked 2 questions at the same time) and this one (which asks about running it as a daemon).

Best Answer

There is a method called decodeURI which can be used to break down the data source URI into the core path and all other components.

The documentation states that this function may not be supported by all provider types, but for delimited text layers and ogr it definitely works as shown below:

>>> layer = iface.activeLayer()
>>> uri_components = QgsProviderRegistry.instance().decodeUri(layer.dataProvider().name(), layer.publicSource());
>>> layer.source()
'file:///D:/Downloads/agency.txt?type=csv&maxFields=10000&detectTypes=yes&geomType=none&subsetIndex=no&watchFile=no'

>>> uri_components['path']
'D:/Downloads/agency.txt'

Related Solutions

PyQGIS – Getting Layer by Name in PyQGIS

UPDATE: 10.04.2018

Using QGIS 3.x you can use the mapLayersByName method from QgsProject class in this way:

layers = QgsProject.instance().mapLayersByName('my layer name')

Since you can have several layers in QGIS with the same name in the layers panel, the method above gives you a list of matching layers.

Before accessing any element in the layer list, you should check if the list has elements. If so you can access, for instance, its first element (layer) in this way:

if layers: 
    layer = layers[0]

Which would be the common case of having a single layer matching the name you searched for.

For QGIS 2.x:

You would just need to make sure your layer has a name you can distinguish from others. Instead of layer = self.iface.activeLayer(), do:

layer=None
for lyr in QgsMapLayerRegistry.instance().mapLayers().values():
    if lyr.name() == "YOUR_LAYER_NAME":
        layer = lyr
        break

If you don't trust the layer name (after all, it can be changed by the user at any time), you could try to check the layer source. If your layer is a Shapefile, you could check the path to the Shapefile, this way:

layer=None
for lyr in QgsMapLayerRegistry.instance().mapLayers().values():
    if lyr.source() == "/path/to/shapefile.shp":
        layer = lyr
        break

EDIT: As @Jakob has pointed out in comments, you can write the first block in one line:

layerList = QgsMapLayerRegistry.instance().mapLayersByName("YOUR_LAYER_NAME")

Or:

layerList = [lyr for lyr in QgsMapLayerRegistry.instance().mapLayers().values() if lyr.name() == "YOUR_LAYER_NAME"]

Anyway, you would need to check that layerList is not empty before accessing its first element:

if layerList: 
    layer = layerList[0]

[GIS] Getting QGIS installation path in PyQGIS

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/

Best Answer

Related Solutions

PyQGIS – Getting Layer by Name in PyQGIS

[GIS] Getting QGIS installation path in PyQGIS

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