django1/django/contrib/gis/gdal/__init__.py

"""
 This module houses ctypes interfaces for GDAL objects.  The following GDAL
 objects are supported:

 CoordTransform: Used for coordinate transformations from one spatial
  reference system to another.

 Driver: Wraps an OGR data source driver.
  
 DataSource: Wrapper for the OGR data source object, supports
  OGR-supported data sources.

 Envelope: A ctypes structure for bounding boxes (GDAL library
  not required).

 OGRGeometry: Layer for accessing OGR Geometry objects.

 OGRGeomType: A class for representing the different OGR Geometry
  types (GDAL library not required).

 SpatialReference: Represents OSR Spatial Reference objects.

 The GDAL library will be imported from the system path using the default  
 library name for the current OS. The default library path may be overridden
 by setting `GDAL_LIBRARY_PATH` in your settings with the path to the GDAL C 
 library on your system.  

 GDAL links to a large number of external libraries that consume RAM when 
 loaded.  Thus, it may desirable to disable GDAL on systems with limited
 RAM resources -- this may be accomplished by setting `GDAL_LIBRARY_PATH`
 to a non-existant file location (e.g., `GDAL_LIBRARY_PATH='/null/path'`; 
 setting to None/False/'' will not work as a string must be given).
"""
import sys

# Attempting to import objects that depend on the GDAL library.  The
# HAS_GDAL flag will be set to True if the library is present on
# the system.
try:
    from django.contrib.gis.gdal.driver import Driver
    from django.contrib.gis.gdal.datasource import DataSource
    from django.contrib.gis.gdal.libgdal import gdal_version, gdal_full_version, gdal_release_date
    from django.contrib.gis.gdal.srs import SpatialReference, CoordTransform
    from django.contrib.gis.gdal.geometries import OGRGeometry, GEOJSON
    HAS_GDAL = True
except:
    HAS_GDAL, GEOJSON = False, False

# The envelope, error, and geomtype modules do not actually require the
# GDAL library, but still nead at least Python 2.4 and ctypes.
PYTHON23 = sys.version_info[0] == 2 and sys.version_info[1] == 3
if not PYTHON23:
    try:
        from django.contrib.gis.gdal.envelope import Envelope
        from django.contrib.gis.gdal.error import check_err, OGRException, OGRIndexError, SRSException
        from django.contrib.gis.gdal.geomtype import OGRGeomType
    except ImportError:
        # No ctypes, but don't raise an exception.
        pass