How do I get the path of a project, or layer file in PyQGIS?

Question

I am generating new raster files from vector layers on a project. I would like to save them in the same directory as the project or layer files. How do I find this path using PyQGIS?

Answer 1

For python console:

QgsProject.instance().readPath("./") # also try "../"

Or with

dir(QgsProject.instance())

you find something like

fileName()

---

For python plugin (not tested!):

from PyQt4.QtGui import QMessageBox
from qgis.core import QgsProject
path_absolute = QgsProject.instance().readPath("./")
QMessageBox.information(None, "Title", "AP: " + unicode(path_absolute))

Answer 2

If you want to access a vector file path, on a active layer, this seems to work:

myfilepath= os.path.dirname( unicode( qgis.utils.iface.activeLayer().dataProvider().dataSourceUri() ) ) ;
fic = myfilepath + "[% "FILE" %]"

then to open a picture or text located in same directory as mylayer:

from PyQt4 import QtWebKit, QtCore ; vue=QtWebKit.QWebView() vue.setUrl( QtCore.QUrl( fic ) ) ; vue.show()