Note that you can specify as many columns as necessary inside the fields variable. The SearchCursor prints a tuple for each row of the attribute table containing the field values for the three specified columns. Using an f-string to print the individual field values for each column in line 6, we reference each column using an index, starting from zero. Note that the three column names are stored in a list variable named ‘fields’, that is referenced when calling the SearchCursor method in line 4. This code snippet listed below shows how to return three different columns from the attribute table data from our Hospitals_England file: the ParentName, City and County columns. SearchCursors only take two required parameters: a table or feature class name, followed by one or multiple field names (= column names) that need to be returned by the SearchCursor object. To start working with SearchCursors, it’s important to understand their syntax, which is specified here. Retrieve column data using a SearchCursor Here, we’ll be using a Feature Service Feature Class downloaded from ArcGIS Online called “Hospitals_England”, which contains a point layer for all hospitals in the UK and needs to be added to the map first by dragging it from the Catalog pane to the map window inside Pro. To follow along, create a new notebook inside ArcGIS Pro and run the code snippets below with a feature class of your choice. In this tutorial, we will show how you can create SearchCursor objects that return column data from a feature class. You can think of a SearchCursor as an iterator as used in a for or while loop, that returns new data with each iteration. ![]() In this tutorial, we willl be using arcpy’s SearchCursor class for returning records from a feature class.Īrcpy’s Data Access module provides the SearchCursor class, from which cursor objects can be created to return records from a feature class or table. It is important to remember, when using an update cursor, do not call the Store method.Using arcpy’s SearchCursor for selecting and returning records When using an update cursor, NextRow is called, the row is edited, and ICursor.UpdateRow is called with the row as a parameter. Using a non-recycling cursor ensures that each geometry is unique.Įxisting rows can be edited with either a search cursor or an update cursor. When using a search cursor, NextRow is called, returning a reference to a row. The row is edited, and IRow.Store is called. This is because a recycling cursor reuses the same geometry and under some circumstances all of the features inserted into the insert cursor may have the same geometry. ![]() Non-recycling feature cursors returned from the Search method *MUST* be used when copying features from the cursor into an insert cursor of another class. ![]() In other words, if the feature retrieved by a search cursor has already been instantiated and is being referenced by the calling application, then a reference to the existing feature object is returned. The Geodatabase guarantees "unique instance semantics" on non-recycling feature objects fetched during an edit session. ![]() The features returned by a non-recycling cursor may be modified and stored with polymorphic behavior. Non-recycling cursors return a separate feature object on each fetch. It is illegal to maintain a reference on a feature object returned by a recycling cursor across multiple calls to NextFeature on the cursor. Features returned by a recycling cursor should not be modified. Recycling cursors rehydrate a single feature object on each fetch and can be used to optimize read-only access, for example, when drawing. The recycling parameter controls row object allocation behavior. If a null value is passed to the filter parameter, the feature cursor will return all of the features from the feature class. Search will return an IFeatureCursor with all of the features that satisfy the attribute and/or spatial constraints as specified by an IQueryFilter reference. Available with ArcGIS Engine, ArcGIS Desktop, and ArcGIS Server.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |