[GRASS-SVN] r43186 - grass/trunk/doc/python
svn_grass at osgeo.org
svn_grass at osgeo.org
Sat Aug 21 22:53:48 EDT 2010
Author: hamish
Date: 2010-08-22 02:53:48 +0000 (Sun, 22 Aug 2010)
New Revision: 43186
Added:
grass/trunk/doc/python/README
grass/trunk/doc/python/m.distance.py
grass/trunk/doc/python/vectoraccess.py
Log:
add README, copy over SWIG examples from swig/python/examples/ (still need to be ported to ctypes)
Added: grass/trunk/doc/python/README
===================================================================
--- grass/trunk/doc/python/README (rev 0)
+++ grass/trunk/doc/python/README 2010-08-22 02:53:48 UTC (rev 43186)
@@ -0,0 +1,17 @@
+There are two ways of using Python to run GRASS commands:
+ (or you could mix them together)
+
+- Module scripting using the grass python helper library and g.parser.
+ import grass.script as grass
+ For examples see scripts/ in the GRASS 7 source code.
+
+
+- Module creation using hooks into the C library functions using ctypes.
+ The scripts in the doc/python/examples/ directory will describe this.
+ (Ctypes is standard in Python 2.5 and newer; replaces the SWIG
+ implementation in GRASS)
+
+
+More details can be found in the GRASS Programmer's Manual.
+
+
Copied: grass/trunk/doc/python/m.distance.py (from rev 43184, grass/trunk/swig/python/examples/m.distance.py)
===================================================================
--- grass/trunk/doc/python/m.distance.py (rev 0)
+++ grass/trunk/doc/python/m.distance.py 2010-08-22 02:53:48 UTC (rev 43186)
@@ -0,0 +1,201 @@
+#!/usr/bin/python
+############################################################################
+#
+# MODULE: m.distance
+#
+# AUTHOR(S): Hamish Bowman, Dunedin, New Zealand
+#
+# PURPOSE: Find distance between two points
+# If the projection is latitude-longitude, this distance
+# is measured along the geodesic.
+# Demonstrates GRASS SWIG-Python interface
+#
+# COPYRIGHT: (c) 2008 Hamish Bowman, and 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.
+#
+############################################################################
+#
+# Requires GRASS SWIG-Python interface
+# Requires Numeric module (NumPy) from http://numpy.scipy.org/
+# Requires NumPrt module from http://geosci.uchicago.edu/csc/numptr/
+#
+
+#%Module
+#% label: Finds the distance between two or more points.
+#% description: If the projection is latitude-longitude, this distance is measured along the geodesic.
+#% keywords: miscellaneous, distance, measure
+#%End
+#%Option
+#% key: coord
+#% type: string
+#% required: no
+#% multiple: yes
+#% key_desc: x,y
+#% description: Comma separated list of coordinate pairs
+#%End
+#%Flag
+#% key: i
+#% description: Read coordinate pairs from stdin
+#%End
+
+
+import os, sys
+
+if not os.environ.has_key("GISBASE"):
+ print "You must be in GRASS GIS to run this program."
+ sys.exit(1)
+
+
+def main():
+
+ #### add your code here ####
+
+ # run this before starting python to append module search path:
+ # export PYTHONPATH=$PYTHONPATH:/usr/local/grass-7.0.svn/etc/python
+ # check with "import sys; sys.path"
+ # or:
+ sys.path.append("/usr/local/grass-7.0.svn/etc/python")
+ from grass.lib import grass as g7lib
+
+ # for passing pointers
+ import Numeric
+ import NumPtr
+
+ g7lib.G_gisinit('m.distance')
+ # returns 0 on success
+
+
+ ### calc distance ###
+
+ proj_type = g7lib.G_begin_distance_calculations()
+ # returns 0 if projection has no metrix (ie. imagery)
+ # returns 1 if projection is planimetric
+ # returns 2 if projection is latitude-longitude
+
+
+ # parser always creates at least an empty variable, and sys.argv is
+ # toast, so no way to check if option was given. So it hangs if
+ # --q was the only option given and there is no data from stdin.
+ coord_ans = os.getenv("GIS_OPT_COORD")
+ stdin_flag = bool(int(os.getenv("GIS_FLAG_I")))
+
+ if stdin_flag is True:
+ coords = []
+ # read line by line from stdin
+ while 1:
+ line = sys.stdin.readline().strip()
+ if not line: # EOF
+ break
+ else:
+ coords += line.split(',')
+ else:
+ # read from coord= command line option
+ coords = coord_ans.split(',')
+
+
+ if len(coords) < 4:
+ print "A minimum of two input coordinate pairs are needed"
+ return
+
+
+ # init variables
+ overall_distance = 0.0
+
+ if proj_type == 2:
+ # lat/lon scan for DDD:MM:SS.SSSS
+ easting = Numeric.array(0., Numeric.Float64)
+ eastPtr = NumPtr.getpointer(easting)
+ northing = Numeric.array(0., Numeric.Float64)
+ northPtr = NumPtr.getpointer(northing)
+
+ # TODO: for clarity, figure out how to replace "3" with
+ # the defined LOCATION_LL constant from gis.i
+ g7lib.G_scan_easting(coords[0], eastPtr, 3)
+ g7lib.G_scan_northing(coords[1], northPtr, 3)
+ x1 = float(easting)
+ y1 = float(northing)
+ else:
+ # plain old coordinates
+ x1 = float(coords[0])
+ y1 = float(coords[1])
+
+ x = [x1]
+ y = [y1]
+
+ for i in range(1, (len(coords) / 2)):
+
+ if proj_type == 2:
+ g7lib.G_scan_easting (coords[ i*2 + 0 ], eastPtr, 3)
+ g7lib.G_scan_northing(coords[ i*2 + 1 ], northPtr, 3)
+ x2 = float(easting)
+ y2 = float(northing)
+ else:
+ x2 = float(coords[ i*2 + 0 ])
+ y2 = float(coords[ i*2 + 1 ])
+
+ segment_distance = g7lib.G_distance(x1, y1, x2, y2)
+ overall_distance += segment_distance
+
+ print "segment %d distance is %.2f meters" % (i, segment_distance)
+
+ # add to the area array
+
+ # setup for the next loop
+ x1 = x2
+ y1 = y2
+
+ x += [x2]
+ y += [y2]
+
+ print
+ print " total distance is %.2f meters" % overall_distance
+ print
+
+
+ ### calc area ###
+ if len(coords) < 6:
+ return
+
+ g7lib.G_begin_polygon_area_calculations()
+ # returns 0 if the projection is not measurable (ie. imagery or xy)
+ # returns 1 if the projection is planimetric (ie. UTM or SP)
+ # returns 2 if the projection is non-planimetric (ie. latitude-longitude)
+
+ # do not need to close polygon (but it doesn't hurt if you do)
+ npoints = len(x)
+
+ # unset variables:
+ #del [Xs, Xptr, Ys, Yptr]
+ # or
+ #Xs = Xptr = Ys = Yptr = None
+
+ Xs = Numeric.array(x, Numeric.Float64)
+ Xptr = NumPtr.getpointer(Xs)
+ Ys = Numeric.array(y, Numeric.Float64)
+ Yptr = NumPtr.getpointer(Ys)
+
+ area = g7lib.G_area_of_polygon(Xptr, Yptr, npoints)
+ print "AREA: %10.2f square meters" % area
+ print
+
+
+ # we don't need this, but just to have a look
+ if False:
+ if proj_type == 1:
+ g7lib.G_database_units_to_meters_factor()
+ # 1.0
+ print "Location units are", g7lib.G_database_unit_name(True)
+
+
+ #### end of your code ####
+ return
+
+if __name__ == "__main__":
+ if ( len(sys.argv) <= 1 or sys.argv[1] != "@ARGS_PARSED@" ):
+ os.execvp("g.parser", [sys.argv[0]] + sys.argv)
+ else:
+ main();
+
Copied: grass/trunk/doc/python/vectoraccess.py (from rev 43184, grass/trunk/swig/python/examples/vectoraccess.py)
===================================================================
--- grass/trunk/doc/python/vectoraccess.py (rev 0)
+++ grass/trunk/doc/python/vectoraccess.py 2010-08-22 02:53:48 UTC (rev 43186)
@@ -0,0 +1,96 @@
+#!/usr/bin/python
+
+# run within GRASS Spearfish session
+# run this before starting python to append module search path:
+# export PYTHONPATH=$PYTHONPATH:/usr/local/grass-7.0.svn/etc/python
+# check with "import sys; sys.path"
+# or:
+# sys.path.append("/usr/local/grass-7.0.svn/etc/python")
+
+import os, sys
+from grass.lib import grass
+from grass.lib import vector as grassvect
+import grass.script as grassscript
+
+if not os.environ.has_key("GISBASE"):
+ print "You must be in GRASS GIS to run this program."
+ sys.exit(1)
+
+if len(sys.argv)==2:
+ input = sys.argv[1]
+else:
+ input = raw_input("Vector Map Name? ")
+
+# initialize
+grass.G_gisinit('')
+
+# find map in search path
+mapset = grass.G_find_vector2(input,'')
+
+# define map structure
+map = grassvect.Map_info()
+
+# define open level (level 2: topology)
+grassvect.Vect_set_open_level (2)
+
+# open existing map
+grassvect.Vect_open_old(map, input, mapset)
+
+# query
+print 'Vect map: ', input
+print 'Vect is 3D: ', grassvect.Vect_is_3d (map)
+print 'Vect DB links: ', grassvect.Vect_get_num_dblinks(map)
+print 'Map Scale: 1:', grassvect.Vect_get_scale(map)
+
+# vector box tests
+box = grassvect.bound_box()
+c_easting1 = 599505.0
+c_northing = 4921010.0
+c_easting2 = 4599505.0
+
+grassvect.Vect_get_map_box(map, box)
+print 'Position 1 in box? ', grassvect.Vect_point_in_box(c_easting1, c_northing, 0, box)
+print 'Position 2 in box? ', grassvect.Vect_point_in_box(c_easting2, c_northing, 0, box)
+print 'Vector line 2 in box? ', grassvect.Vect_get_line_box(map, 2, box)
+# misleading:
+# print 'Number of lines:', grassvect.Vect_get_num_lines(map)
+# how to access GV_POINT?
+# print 'Number of points: ', grassvect.Vect_get_num_primitives(map,GV_POINT)
+# confusing:
+#print 'Number of lines: ', grassvect.Vect_get_num_primitives(map,GV_LINE)
+#print 'Number of areas:', grassvect.Vect_get_num_primitives(map,GV_AREA)
+print 'Number of areas:', grassvect.Vect_get_num_areas(map)
+
+layer = 1
+tmp = grassscript.tempfile()
+tmpf = file(tmp, 'w')
+
+try:
+ f = grassscript.vector_db(input)[int(layer)]
+except KeyError:
+ grassscript.fatal("There is no table connected to this map. Run v.db.connect or v.db.addtable first.")
+table = f['table']
+database = f['database']
+driver = f['driver']
+
+# call GRASS command
+grassscript.run_command('v.db.select', flags = 'c', map = input,
+ stdout = tmpf)
+tmpf.close()
+
+# check if result is empty
+tmpf = file(tmp)
+if tmpf.read(1) == '':
+ grassscript.fatal("Table <%s> contains no data.", table)
+
+# print table to stdout
+for line in tmpf:
+ print line
+
+tmpf.close()
+os.remove(tmp)
+
+# close map
+grassvect.Vect_close(map)
+## end of the python script
+
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