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115 lines
4.1 KiB
115 lines
4.1 KiB
# The GDAL C library, OGR exception, and the Field object |
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from django.contrib.gis.gdal.error import OGRException, OGRIndexError |
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from django.contrib.gis.gdal.field import Field |
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from django.contrib.gis.gdal.geometries import OGRGeometry, OGRGeomType |
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from django.contrib.gis.gdal.srs import SpatialReference |
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# ctypes function prototypes |
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from django.contrib.gis.gdal.prototypes.ds import \ |
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destroy_feature, feature_equal, get_fd_geom_type, get_feat_geom_ref, \ |
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get_feat_name, get_feat_field_count, get_fid, get_field_defn, \ |
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get_field_index, get_field_name |
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from django.contrib.gis.gdal.prototypes.geom import clone_geom, get_geom_srs |
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from django.contrib.gis.gdal.prototypes.srs import clone_srs |
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# For more information, see the OGR C API source code: |
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# http://www.gdal.org/ogr/ogr__api_8h.html |
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# |
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# The OGR_F_* routines are relevant here. |
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class Feature(object): |
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"A class that wraps an OGR Feature, needs to be instantiated from a Layer object." |
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#### Python 'magic' routines #### |
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def __init__(self, feat, fdefn): |
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"Initializes on the pointers for the feature and the layer definition." |
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self._ptr = None # Initially NULL |
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if not feat or not fdefn: |
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raise OGRException('Cannot create OGR Feature, invalid pointer given.') |
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self._ptr = feat |
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self._fdefn = fdefn |
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def __del__(self): |
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"Releases a reference to this object." |
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if self._ptr: destroy_feature(self._ptr) |
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def __getitem__(self, index): |
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""" |
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Gets the Field object at the specified index, which may be either |
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an integer or the Field's string label. Note that the Field object |
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is not the field's _value_ -- use the `get` method instead to |
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retrieve the value (e.g. an integer) instead of a Field instance. |
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""" |
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if isinstance(index, basestring): |
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i = self.index(index) |
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else: |
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if index < 0 or index > self.num_fields: |
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raise OGRIndexError('index out of range') |
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i = index |
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return Field(self._ptr, i) |
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def __iter__(self): |
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"Iterates over each field in the Feature." |
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for i in xrange(self.num_fields): |
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yield self[i] |
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def __len__(self): |
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"Returns the count of fields in this feature." |
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return self.num_fields |
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def __str__(self): |
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"The string name of the feature." |
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return 'Feature FID %d in Layer<%s>' % (self.fid, self.layer_name) |
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def __eq__(self, other): |
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"Does equivalence testing on the features." |
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return bool(feature_equal(self._ptr, other._ptr)) |
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#### Feature Properties #### |
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@property |
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def fid(self): |
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"Returns the feature identifier." |
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return get_fid(self._ptr) |
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@property |
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def layer_name(self): |
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"Returns the name of the layer for the feature." |
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return get_feat_name(self._fdefn) |
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@property |
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def num_fields(self): |
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"Returns the number of fields in the Feature." |
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return get_feat_field_count(self._ptr) |
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@property |
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def fields(self): |
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"Returns a list of fields in the Feature." |
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return [get_field_name(get_field_defn(self._fdefn, i)) |
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for i in xrange(self.num_fields)] |
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@property |
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def geom(self): |
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"Returns the OGR Geometry for this Feature." |
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# Retrieving the geometry pointer for the feature. |
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geom_ptr = get_feat_geom_ref(self._ptr) |
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return OGRGeometry(clone_geom(geom_ptr)) |
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@property |
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def geom_type(self): |
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"Returns the OGR Geometry Type for this Feture." |
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return OGRGeomType(get_fd_geom_type(self._fdefn)) |
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#### Feature Methods #### |
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def get(self, field): |
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""" |
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Returns the value of the field, instead of an instance of the Field |
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object. May take a string of the field name or a Field object as |
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parameters. |
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""" |
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field_name = getattr(field, 'name', field) |
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return self[field_name].value |
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def index(self, field_name): |
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"Returns the index of the given field name." |
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i = get_field_index(self._ptr, field_name) |
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if i < 0: raise OGRIndexError('invalid OFT field name given: "%s"' % field_name) |
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return i
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