[GRASS-dev] [GRASS GIS] #2424: PyGRASS does not work when GRASS is invoked from outside

[GRASS GIS]

#2424: PyGRASS  does not work when GRASS is invoked from outside
-------------------------+-------------------------------------------------
  Reporter:  wenzeslaus  |      Owner:  grass-dev@…
      Type:  defect      |     Status:  new
  Priority:  normal      |  Milestone:  7.2.3
 Component:  Python      |    Version:  svn-trunk
  ctypes                 |   Keywords:  installation, pygrass, temporal,
Resolution:              |  scripts
       CPU:              |   Platform:  MSWindows 8
  Unspecified            |
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Comment (by wenzeslaus):

 These both help, but just to clarify, here we are concerned with only the
 part of the Python API which uses `ctypes` in the background, i.e. not
 `grass.script` which works just fine, but with `grass.temporal` and a
 significant part of `grass.pygrass`.

 Replying to [comment:12 neteler]:
 >  * Python: GRASS GIS 7 with an external library: grass-session:

 This makes using `grass.script` much easier, but it is not possible to use
 anything which calls ''ctypes'' (`grass.lib`), i.e. `grass.temporal` and
 `grass.pygrass`, unless the dynamic libraries are loaded in some special
 way (just changing `LD_LIBRARY_PATH` was not enough so far). (From
 `grass.pygrass` I mean the part using `ctypes`, otherwise see the
 comment:3 to comment:6 here.)

 >  * New easy-to-use CLI and API for GRASS GIS

 In past your would have to do this (see comment:6 for details):

 {{{
 export LD_LIBRARY_PATH=$(grass70 --config path)/lib
 python script_with_ctypes.py
 }}}

 Since 7.2 (after #2579, i.e. r65252), you can (see again comment:6 for
 details):

 {{{
 grass ~/grassdata/nc_spm/test/ --exec script_with_ctypes.py
 }}}

 In regard to this ticket, the proposed CLI would work similarly to current
 `--exec`. Same goes to the proposed Python API and the current APIs.

 Nevertheless, `--exec` and the proposed CLI interface reduce the need to
 load the libraries, for example, because the recommended way of using them
 is to write a GRASS module and then call it using `--exec` - this way the
 GRASS-specific part of the program is isolated and at the same time usable
 as a separate GRASS module.

-- 
Ticket URL: <https://trac.osgeo.org/grass/ticket/2424#comment:13>
GRASS GIS <https://grass.osgeo.org>