Changes between Version 15 and Version 16 of PythonGotchas

Timestamp:

Oct 24, 2013, 3:22:28 PM (10 years ago)

Author:

sudobangbang

Comment:

updated comments for SetAttributeFilter

PythonGotchas

@@ -124 +124 @@
 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, if you use {{{GetFeature()}}} instead of {{{GetNextFeature()}}}, 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. :
+=== 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 if you use {{{GetFeature()}}}, instead of {{{GetNextFeature()}}}, then you can still access and work with features from the layer that are not covered by the filter. {{{GetFeatureCount()}}} will respect the filter and show the correct number of features filtered. However, working with {{{GetFeatureCount()}}} in a loop can lead to some subtle confusion. Iterating over the {{{Layer}}} object or using {{{GetNextFeature()}}} should be the default method for accessing features:
 
 {{{
@@ -134 +134 @@
 >>> 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  
+...    print feat                                     # this will print one feat, but it's the first feat in the Layer and not the filtered feat  
 ...
 }}}