Exception using PyGRASS: "No module named 'core'"

Question

I am trying PyGRASS on Ubuntu 14.04. I have GRASS 7 installed from the UbuntuGIS PPA:

$ dpkg -l | grep grass
ii  grass                                                       7.0.4-1~trusty1                                     all          Geographic Resources Analysis Support System (GRASS GIS)
ii  grass-core                                                  7.0.4-1~trusty1                                     amd64        GRASS GIS core components
ii  grass-dev                                                   7.0.4-1~trusty1                                     amd64        GRASS GIS development files
ii  grass-doc                                                   7.0.4-1~trusty1                                     all          GRASS GIS user documentation
ii  grass-gui                                                   7.0.4-1~trusty1                                     amd64        GRASS GIS graphical user interfaces
ii  libqgisgrass2.0.1                                           2.0.1-2build2                                       amd64        QGIS - shared libraries (libqgisgrass)
ii  libqgisgrass2.8.1                                           1:2.8.1-0+20trusty6                                 amd64        QGIS - shared grass library
ii  libqgisgrass7-2.14.0                                        1:2.14.0+20trusty-ubuntugis                         amd64        QGIS - shared grass library
ii  libqgisgrass7-2.14.1                                        1:2.14.1+20trusty-ubuntugis                         amd64        QGIS - shared grass library
ii  libqgisgrass7-2.14.2                                        1:2.14.2+20trusty-ubuntugis                         amd64        QGIS - shared grass library
ii  libqgisgrass7-2.14.3                                        1:2.14.3+20trusty-ubuntugis                         amd64        QGIS - shared grass library
ii  qgis-plugin-grass                                           1:2.14.3+20trusty-ubuntugis                         amd64        GRASS plugin for QGIS
ii  qgis-plugin-grass-common                                    1:2.14.3+20trusty-ubuntugis                         all          GRASS plugin for QGIS - architecture-independent data
ii  qgis-provider-grass                                         1:2.14.3+20trusty-ubuntugis                         amd64        GRASS provider for QGIS

I created a small script inspired on Example 4 of the Python and GRASS wiki page:

#!/usr/bin/env python

# Example for pyGRASS usage - vector API

from grass.pygrass.modules.shortcuts import general as g
from grass.pygrass.vector import VectorTopo
from grass.pygrass.modules import Module

vectmap = 'myzipcodes_wake'

g.message("Importing SHAPE file ...")
ogrimport = Module('v.in.ogr')
ogrimport('/home/neteler/gis_data/zipcodes_wake.shp', output=vectmap)

g.message("Assessing vector topology...")
zipcodes = VectorTopo(vectmap)

# Open the map with topology:
zipcodes.open()

# query number of topological features
areas   = zipcodes.number_of("areas")
islands = zipcodes.number_of("islands")
print ('Map: <' + vectmap + '> with %d areas and %d islands' % (areas, islands))

dblink = zipcodes.dblinks[0]
print ('DB name:')
print (dblink.database)
table = dblink.table()
print ('Column names:')
print (table.columns.names())
print ('Column types:')
print (table.columns.types())

zipcodes.close()

But its execution fails with an ImportError exception:

$ python3 pygrass-demo4.py
Traceback (most recent call last):
  File "pygrass-demo4.py", line 5, in <module>
    from grass.pygrass.modules.shortcuts import general as g
  File "/usr/lib/grass70/etc/python/grass/pygrass/modules/__init__.py", line 2, in <module>
    from grass.pygrass.modules.interface import Module, ParallelModuleQueue
  File "/usr/lib/grass70/etc/python/grass/pygrass/modules/interface/__init__.py", line 9, in <module>
    from grass.pygrass.modules.interface import module
  File "/usr/lib/grass70/etc/python/grass/pygrass/modules/interface/module.py", line 10, in <module>
    from grass.script.core import Popen, PIPE
  File "/usr/lib/grass70/etc/python/grass/script/__init__.py", line 4, in <module>
    from core   import *
ImportError: No module named 'core'

Do I need to install any other library to use PyGRASS? Or is there something else wrong?

Update I: According to Gene, PyGRASS must be run in a Python 2 environment. However, it only produces a different exception:

Traceback (most recent call last):
  File "/home/desouslu/git/pywps-4-demo/processes/pygrass-demo4.py", line 6, in <module>
    from grass.pygrass.vector import VectorTopo
  File "/usr/lib/grass70/etc/python/grass/pygrass/vector/__init__.py", line 3, in <module>
    import grass.lib.gis as libgis
  File "/usr/lib/grass70/etc/python/grass/lib/gis.py", line 23, in <module>
    _libs["grass_gis.7.0.4"] = load_library("grass_gis.7.0.4")
  File "/usr/lib/grass70/etc/python/grass/lib/ctypes_loader.py", line 57, in load_library
    raise ImportError,"%s not found." % libname
ImportError: grass_gis.7.0.4 not found.

Update II: User Gene suggests a problem with Eclipse itself. However, executing the script from the command line produces the same results:

$ python pygrass-demo4.py 
Traceback (most recent call last):
  File "pygrass-demo4.py", line 6, in <module>
    from grass.pygrass.vector import VectorTopo
  File "/usr/lib/grass70/etc/python/grass/pygrass/vector/__init__.py", line 3, in <module>
    import grass.lib.gis as libgis
  File "/usr/lib/grass70/etc/python/grass/lib/gis.py", line 23, in <module>
    _libs["grass_gis.7.0.4"] = load_library("grass_gis.7.0.4")
  File "/usr/lib/grass70/etc/python/grass/lib/ctypes_loader.py", line 57, in load_library
    raise ImportError,"%s not found." % libname
ImportError: grass_gis.7.0.4 not found.

Or alternatively using the Python console:

$ python
Python 2.7.6 (default, Jun 22 2015, 17:58:13) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from grass.pygrass.modules.shortcuts import general as g
>>> from grass.pygrass.vector import VectorTopo
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/grass70/etc/python/grass/pygrass/vector/__init__.py", line 3, in <module>
    import grass.lib.gis as libgis
  File "/usr/lib/grass70/etc/python/grass/lib/gis.py", line 23, in <module>
    _libs["grass_gis.7.0.4"] = load_library("grass_gis.7.0.4")
  File "/usr/lib/grass70/etc/python/grass/lib/ctypes_loader.py", line 57, in load_library
    raise ImportError,"%s not found." % libname
ImportError: grass_gis.7.0.4 not found.

You run the script in GRASS or from outside ? – gene Jun 16 '16 at 15:01 — gene, Jun 16 '16 at 15:01
I am running the script from Eclipse. – Luís de Sousa Jun 17 '16 at 12:40 — Luís de Sousa, Jun 17 '16 at 12:40

score 1 · Accepted Answer · edited May 23 '17 at 12:39

The Python version of GRASS GIS is 2.7.x and not 3.x

In Python 2.7.11 (Mac OS X)

import grass.script.core 
core.__file__
 '/Applications/GRASS-7.0.app/Contents/MacOS/etc/python/grass/script/core.pyc

In Python 3.5.1

 import grass.script.core
 Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
  File "/Applications/GRASS-7.0.app/Contents/MacOS/etc/python/grass/script/__init__.py", line 4, in <module>
from core   import *
ImportError: No module named 'core'

Why ? This is because Python 3 changes the syntax for imports from within a package (look at Changes in import statement python 3, for example)

In the init.py (/.../python/grass/script/init.py)

"""Python interface to launch GRASS GIS modules in scripts
"""
from core   import *
....

In Python 3.x this should be

from .core import *

This syntax is also valid for Python 2.7.x

New

I don't understand your question because:

the first thing you need is to run GRASS GIS from outside and you haven't found the solution in your case (grass_gis.7.0.4 not found and GRASS 7 environment setup for Python)
the solution that I have given you is for working in the Python shell or in a IPython/Jupyter notebook, not in Ellipse and it works in my case (with GRASS 7.04 or GRASS 7.1 in Mac OS X or LinuxMint)
If you want to use Ellipe, there are wikis in the GRASS site (Eclipse, Using Eclipse to develop GRASS Python programs) and answers in GIS SE (as Difference between python IDLE and eclipse on accessing GRASS)

Therefore, for me, the main problem is 1). Have you tried the Python script GRASS GIS 7 with existing location ?

It does not run with Python 2 either, could you please the check the update to the question? If this other exception is something else then I should accept this answer. — Luís de Sousa, Jun 17 '16 at 12:39
This exception is not related to Eclipse, please check the update to the question. — Luís de Sousa, Jun 20 '16 at 07:04
The LD_LIBRARY_PATH variable was not being set up correctly. So the main problem was really using the Python 3 interpreter instead of Python 2. — Luís de Sousa, Jun 20 '16 at 09:01

Exception using PyGRASS: "No module named 'core'"

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