Changes between Version 13 and Version 14 of PythonGotchas

Timestamp:

Oct 23, 2013, 12:30:57 PM (11 years ago)

Author:

sudobangbang

Comment:

added subtle reminder about SetAttributeFilter adn GetNextFeature

PythonGotchas

@@ -123 +123 @@
 
 For more information, please see #3552.
+
+=== Layers with attribute filters {{{SetAttributeFilter()}}} will only return filtered features when using {{{GetNextFeature()}}} ===
+
+If you read the documentation for {{{SetAttributeFilter()}}} carefully you will see the caveat about {{{OGR_L_GetNextFeature()}}}. This means that you can still access and work with features from the layer that are not covered by the filter. In combination with {{{GetFeatureCount()}}} as a loop, this can lead to some subtle confusion. Iterating over the {{{Layer}}} object or using {{{GetNextFeature()}}} should be the default method for accessing features:
+
+{{{
+#!python
+>>> lyr = inDataSource.GetLayer()
+>>> lyr.SetAttributeFilter("PIN = '0000200001'")      # this is a unique filter for only one record
+>>> for i in range( 0, lyr.GetFeatureCount() ):
+...    feat = lyr.GetFeature( i )
+...    print feat                                     # this will print out every feature in the layer disregarding the filter  
+...
+}}}
+
 
 === Certain objects contain a {{{Destroy()}}} method, but you should never use it ===