grass.pygrass.rpc package

Fast and exit-safe interface to PyGRASS Raster and Vector layer using multiprocessing

(C) 2015 by the GRASS Development Team This program is free software under the GNU General Public License (>=v2). Read the file COPYING that comes with GRASS for details.

authors

Soeren Gebbert

class grass.pygrass.rpc.DataProvider

Bases: grass.pygrass.rpc.base.RPCServerBase

Fast and exit-safe interface to PyGRASS data delivery functions

get_raster_image_as_np(name, mapset=None, extent=None, color='RGB')

Return the attribute table of a vector map as dictionary.

See documentation of: pygrass.raster.raster2numpy_img

Usage:

>>> from grass.pygrass.rpc import DataProvider
>>> import time
>>> provider = DataProvider()
>>> ret = provider.get_raster_image_as_np(name=test_raster_name)
>>> len(ret)
64

>>> extent = {"north":30, "south":10, "east":30, "west":10,
...           "rows":2, "cols":2}
>>> ret = provider.get_raster_image_as_np(name=test_raster_name,
...                                       extent=extent)
>>> len(ret)
16

>>> extent = {"rows":3, "cols":1}
>>> ret = provider.get_raster_image_as_np(name=test_raster_name,
...                                       extent=extent)
>>> len(ret)
12

>>> extent = {"north":100, "south":10, "east":30, "west":10,
...           "rows":2, "cols":2}
>>> ret = provider.get_raster_image_as_np(name=test_raster_name,
...                                       extent=extent)

>>> provider.stop()
>>> time.sleep(1)

>>> extent = {"rows":3, "cols":1}
>>> ret = provider.get_raster_image_as_np(name=test_raster_name,
...                                       extent=extent)
>>> len(ret)
12


..

get_vector_features_as_wkb_list(name, mapset=None, extent=None, feature_type='point', field=1)

Return the features of a vector map as wkb list.

Parameters

• extent – A dictionary of {“north”:double, “south”:double, “east”:double, “west”:double}

• feature_type – point, centroid, line, boundary or area

See documentation: pygrass.vector.VectorTopo::features_to_wkb_list

pygrass.vector.VectorTopo::areas_to_wkb_list

Usage:

>>> from grass.pygrass.rpc import DataProvider
>>> provider = DataProvider()
>>> wkb = provider.get_vector_features_as_wkb_list(name=test_vector_name,
...                                                extent=None,
...                                                feature_type="point")
>>> for entry in wkb:
...     f_id, cat, string = entry
...     print(f_id, cat, len(string))
1 1 21
2 1 21
3 1 21

>>> extent = {"north":6.6, "south":5.5, "east":14.5, "west":13.5}
>>> wkb = provider.get_vector_features_as_wkb_list(name=test_vector_name,
...                                                extent=extent,
...                                                feature_type="point")
>>> for entry in wkb:
...     f_id, cat, string = entry
...     print(f_id, cat, len(string))
3 1 21

>>> wkb = provider.get_vector_features_as_wkb_list(name=test_vector_name,
...                                                extent=None,
...                                                feature_type="line")
>>> for entry in wkb:
...     f_id, cat, string = entry
...     print(f_id, cat, len(string))
4 2 57
5 2 57
6 2 57


>>> wkb = provider.get_vector_features_as_wkb_list(name=test_vector_name,
...                                                extent=None,
...                                                feature_type="centroid")
>>> for entry in wkb:
...     f_id, cat, string = entry
...     print(f_id, cat, len(string))
19 3 21
18 3 21
20 3 21
21 3 21

>>> wkb = provider.get_vector_features_as_wkb_list(name=test_vector_name,
...                                                extent=None,
...                                                feature_type="area")
>>> for entry in wkb:
...     f_id, cat, string = entry
...     print(f_id, cat, len(string))
1 3 225
2 3 141
3 3 93
4 3 141

>>> wkb = provider.get_vector_features_as_wkb_list(name=test_vector_name,
...                                                extent=None,
...                                                feature_type="boundary")
>>> for entry in wkb:
...     f_id, cat, string = entry
...     print(f_id, cat, len(string))
10 None 41
7 None 41
8 None 41
9 None 41
11 None 89
12 None 41
14 None 41
13 None 41
17 None 41
15 None 41
16 None 41

>>> provider.stop()

..

get_vector_table_as_dict(name, mapset=None, where=None)

Return the attribute table of a vector map as dictionary.

See documentation of: pygrass.vector.VectorTopo::table_to_dict

Usage:

>>> from grass.pygrass.rpc import DataProvider
>>> provider = DataProvider()
>>> ret = provider.get_vector_table_as_dict(name=test_vector_name)
>>> ret["table"]
{1: [1, 'point', 1.0], 2: [2, 'line', 2.0], 3: [3, 'centroid', 3.0]}
>>> ret["columns"]
Columns([('cat', 'INTEGER'), ('name', 'varchar(50)'), ('value', 'double precision')])
>>> ret = provider.get_vector_table_as_dict(name=test_vector_name,
...                                           where="value > 1")
>>> ret["table"]
{2: [2, 'line', 2.0], 3: [3, 'centroid', 3.0]}
>>> ret["columns"]
Columns([('cat', 'INTEGER'), ('name', 'varchar(50)'), ('value', 'double precision')])
>>> provider.get_vector_table_as_dict(name="no_map",
...                                   where="value > 1")
>>> provider.stop()

..

start_server()

This function must be re-implemented in the subclasses

class grass.pygrass.rpc.RPCDefs

Bases: object

GET_RASTER_IMAGE_AS_NP = 3

GET_VECTOR_FEATURES_AS_WKB = 2

GET_VECTOR_TABLE_AS_DICT = 1

G_FATAL_ERROR = 14

STOP = 0

grass.pygrass.rpc.data_provider_server(lock, conn)

The PyGRASS data provider server designed to be a target for multiprocessing.Process

Parameters

• lock – A multiprocessing.Lock

• conn – A multiprocessing.Pipe

Submodules

grass.pygrass.rpc.base module

Fast and exit-safe interface to PyGRASS Raster and Vector layer using multiprocessing

(C) 2015 by the GRASS Development Team This program is free software under the GNU General Public License (>=v2). Read the file COPYING that comes with GRASS for details.

authors

Soeren Gebbert

class grass.pygrass.rpc.base.RPCServerBase

Bases: object

This is the base class for send and receive RPC server It uses a Pipe for IPC.

>>> import grass.script as gscript
>>> from grass.pygrass.rpc.base import RPCServerBase
>>> import time
>>> provider = RPCServerBase()

>>> provider.is_server_alive()
True

>>> provider.is_check_thread_alive()
True

>>> provider.stop()
>>> time.sleep(1)
>>> provider.is_server_alive()
False

>>> provider.is_check_thread_alive()
False

>>> provider = RPCServerBase()
>>> provider.is_server_alive()
True
>>> provider.is_check_thread_alive()
True

Kill the server process with an exception, it should restart

>>> provider.client_conn.send([1])
>>> provider.is_server_alive()
True

>>> provider.is_check_thread_alive()
True

check_server()

is_check_thread_alive()

is_server_alive()

safe_receive(message)

Receive the data and throw a FatalError exception in case the server process was killed and the pipe was closed by the checker thread

start_checker_thread()

start_server()

This function must be re-implemented in the subclasses

stop()

Stop the check thread, the libgis server and close the pipe

This method should be called at exit using the package atexit

stop_checker_thread()

thread_checker()

Check every 200 micro seconds if the server process is alive

grass.pygrass.rpc.base.dummy_server(lock, conn)

Dummy server process

Parameters

• lock – A multiprocessing.Lock

• conn – A multiprocessing.Pipe