[GRASS-dev] RE: [GRASS-user] Question with Python-SWIG example [SEC=UNCLASSIFIED]

[Glynn Clements]

Martin Landa wrote:

> > it shouldn't be possible for this:
> >
> >        G_find_raster2.argtypes = [c_char_p, c_char_p]
> >        G_find_raster2.restype = c_char_p
> >
> > to work but this:
> >
> >        G_find_raster2.argtypes = [String, String]
> >        G_find_raster2.restype = ReturnString
> 
> Here I am getting
> 
> Traceback (most recent call last):
>   File "/home/martin/smetiste/example7.py", line 8, in <module>
>     grass.G_find_raster2.argtypes = [String, String]
> NameError: name 'String' is not defined
> 
> even ctypes are imported (from ctypes import *).

String and ReturnString are defined in ctypes_preamble.py and imported
into the individual wrapper modules (e.g. grass.py). They should be
visible within the script as grass.String, etc.

G_find_raster2 is (or should be) defined in grass.py as:

	# /usr/local/src/grass/7.0/dist.i686-pc-linux-gnu/include/grass/gisdefs.h: 220
	if hasattr(_libs['grass_gis'], 'G_find_raster2'):
	    G_find_raster2 = _libs['grass_gis'].G_find_raster2
	    G_find_raster2.restype = ReturnString
	    G_find_raster2.argtypes = [String, String]

The only imports in grass.py are:

	from ctypes_preamble import *
	from ctypes_preamble import _variadic_function
	from ctypes_loader import *

so it shouldn't be possible for it to pick up some other definition
for "String".

It's annoying that the error message doesn't indicate which class's
__init__ method is involved, or  the traceback.

Some other things to check:

	> from grass.lib import grass
	> grass.String
	<class 'ctypes.c_char_p'>
	> grass.ReturnString
	<class 'ctypes.c_char_p'>
	> grass.G_find_raster2
	<_FuncPtr object at 0x827eecc>
	> grass.G_find_raster2.__class__
	<class 'ctypes._FuncPtr'>
	> grass.G_find_raster2.argtypes
	[<class 'ctypes.c_char_p'>, <class 'ctypes.c_char_p'>]
	> grass.G_find_raster2.restype
	<class 'ctypes.c_char_p'>
	> grass.G_find_raster2._restype_
	<class 'ctypes.c_long'>
	> grass.G_find_raster2._objects
	{'0': <CDLL '/usr/local/src/grass/svn/dist.i686-pc-linux-gnu/lib/libgrass_gis.so', handle 8193e88 at 824f32c>}

-- 
Glynn Clements <glynn at gclements.plus.com>