/django/contrib/gis/gdal/feature.py
Python | 110 lines | 96 code | 5 blank | 9 comment | 3 complexity | d3700e6e05ab1e614345cfff0c8086f3 MD5 | raw file
Possible License(s): BSD-3-Clause
- # The GDAL C library, OGR exception, and the Field object
- from django.contrib.gis.gdal.base import GDALBase
- from django.contrib.gis.gdal.error import OGRException, OGRIndexError
- from django.contrib.gis.gdal.field import Field
- from django.contrib.gis.gdal.geometries import OGRGeometry, OGRGeomType
- from django.contrib.gis.gdal.srs import SpatialReference
- # ctypes function prototypes
- from django.contrib.gis.gdal.prototypes import ds as capi, geom as geom_api
- # For more information, see the OGR C API source code:
- # http://www.gdal.org/ogr/ogr__api_8h.html
- #
- # The OGR_F_* routines are relevant here.
- class Feature(GDALBase):
- "A class that wraps an OGR Feature, needs to be instantiated from a Layer object."
- #### Python 'magic' routines ####
- def __init__(self, feat, fdefn):
- "Initializes on the pointers for the feature and the layer definition."
- if not feat or not fdefn:
- raise OGRException('Cannot create OGR Feature, invalid pointer given.')
- self.ptr = feat
- self._fdefn = fdefn
- def __del__(self):
- "Releases a reference to this object."
- if self._ptr: capi.destroy_feature(self._ptr)
- def __getitem__(self, index):
- """
- Gets the Field object at the specified index, which may be either
- an integer or the Field's string label. Note that the Field object
- is not the field's _value_ -- use the `get` method instead to
- retrieve the value (e.g. an integer) instead of a Field instance.
- """
- if isinstance(index, basestring):
- i = self.index(index)
- else:
- if index < 0 or index > self.num_fields:
- raise OGRIndexError('index out of range')
- i = index
- return Field(self.ptr, i)
-
- def __iter__(self):
- "Iterates over each field in the Feature."
- for i in xrange(self.num_fields):
- yield self[i]
- def __len__(self):
- "Returns the count of fields in this feature."
- return self.num_fields
-
- def __str__(self):
- "The string name of the feature."
- return 'Feature FID %d in Layer<%s>' % (self.fid, self.layer_name)
- def __eq__(self, other):
- "Does equivalence testing on the features."
- return bool(capi.feature_equal(self.ptr, other._ptr))
- #### Feature Properties ####
- @property
- def fid(self):
- "Returns the feature identifier."
- return capi.get_fid(self.ptr)
-
- @property
- def layer_name(self):
- "Returns the name of the layer for the feature."
- return capi.get_feat_name(self._fdefn)
- @property
- def num_fields(self):
- "Returns the number of fields in the Feature."
- return capi.get_feat_field_count(self.ptr)
- @property
- def fields(self):
- "Returns a list of fields in the Feature."
- return [capi.get_field_name(capi.get_field_defn(self._fdefn, i))
- for i in xrange(self.num_fields)]
- @property
- def geom(self):
- "Returns the OGR Geometry for this Feature."
- # Retrieving the geometry pointer for the feature.
- geom_ptr = capi.get_feat_geom_ref(self.ptr)
- return OGRGeometry(geom_api.clone_geom(geom_ptr))
- @property
- def geom_type(self):
- "Returns the OGR Geometry Type for this Feture."
- return OGRGeomType(capi.get_fd_geom_type(self._fdefn))
-
- #### Feature Methods ####
- def get(self, field):
- """
- Returns the value of the field, instead of an instance of the Field
- object. May take a string of the field name or a Field object as
- parameters.
- """
- field_name = getattr(field, 'name', field)
- return self[field_name].value
- def index(self, field_name):
- "Returns the index of the given field name."
- i = capi.get_field_index(self.ptr, field_name)
- if i < 0: raise OGRIndexError('invalid OFT field name given: "%s"' % field_name)
- return i