Running processing toolbox outside QGIS in standalone app?

Question

I am developing a standalone app in Python, using QGIS libraries including processing algorithms. I am developing in Linux environment and I put the libraries in a folder. Also I put the processing folder from QGIS in that same folder. I run the app but when I import the processing folder, it gives me nothing (not even error messages).

I import like that:

import processing.core.Processing

Can you help me?

CODE:

import sys
import qgis.core
import PyQt4.QtCore
import PyQt4.QtGui
app = qgis.core.QgsApplication([],True)
qgis.core.QgsApplication.setPrefixPath("/usr", True)
qgis.core.QgsApplication.initQgis()

(from here the program doesn't work)

from processing.core.Processing import Processing
inputLayer = 'c:....'
inputMask = 'c:....'

extent = ....
cellsize = ....
outPath = 'c:.....'

Processing.Initialize()
Processing.runalgorith(.....)

---

I downloaded the folder with the processing version 2.2.0-2 and I copied to my script folder. I run and it gives me this error:

Traceback (most recent call last):
  File "teste.py", line 12, in <module>
    from processing.core.Processing import Processing
  File "/home/p/Programas/processing/__init__.py", line 28, in <module>
    from processing.tools.dataobjects import *
  File "/home/p/Programas/processing/tools/dataobjects.py", line 33, in <module>
    from processing.core.ProcessingConfig import ProcessingConfig
  File "/home/p/Programas/processing/core/ProcessingConfig.py", line 30, in <module>
    from processing.tools.system import *
  File "/home/p/Programas/processing/core/processing.py", line 33, in <module>
    from processing import interface
ImportError: cannot import name interface

---

I got it!! What is missing in my case was to define the PYTHONPATH to the folder with the processing. Now I have the correct running of the code.

Answer 1

Right, I've tested your script and, as you say it doesn't throw anything (not even errors) when I run it.

Try instead this script, it works for me on Linux, emulating your scenario (moving processing folder to my script folder):

# Prepare the environment
import sys
from qgis.core import QgsApplication
from PyQt4.QtGui import QApplication
app = QApplication([])
QgsApplication.setPrefixPath("/usr", True)
QgsApplication.initQgis()

# Prepare processing framework 
sys.path.append('/home/YOUR_USER/.qgis2/python/plugins')
from processing.core.Processing import Processing
Processing.initialize()

print Processing.getAlgorithm("qgis:creategrid")

# Exit applications
QgsApplication.exitQgis()
QApplication.exit()