Extending Python Doing more than just interfacing with the geoprocessor Free example utility for NZ Projections Kim Ollivier

Extending Python Gluing it all together strong -> weak Your own Python modules for utilities Other Python modules eg ODBC, XML Other COM interfaces eg Excel ArcGIS toolbox for forms interface ESRI Geoprocessor COM object VBA for ArcMap graphical interaction

Extending Python Helpers and Hints Good idea to use Python 2.4 Python extensions do anything Early binding for COM (Makepy) Direct Python interfaces are best Samples toolbox in 9.1 are a start Maybe contribute your own?

Extending Python Python Modules import mymodule – that’s all there is to it! Would contain your own pythonic functions and classes, documentation, test code Port your arc-only aml utilities My example module is called corax (etools has gone) Do not depend on toolbox validation

Extending Python Creating an NZ Grid Index 1.Decide on the series scale 2.Get the limits for the index: eg Prime name or coordinates or interactive. For interactive input you have to use VBA, UITool, save results to a file. 3.Repeatedly call a function to get [name,extent]…for each sheet in the list 4.Output polys direct or Create a text file 5.Add as a layer or Create the index

Extending Python Step 1 Make a list of sheets Get limits [xmin,ymin,xmax,ymax] Find the sheets at lower left and top right [name,bound] = corax.nztmsheet(scale,x,y) Create a [list] of [name,x1,y1,x2,y2]… Name has 4 parts: prime-scale_col.row

Extending Python Step 2 Get extents of sheets Use the module with custom functions import corax [name,bounds] = corax.nztmsheet(scale,x,y) Add to [list] of [name,x1,y1,x2,y2]…

Extending Python Step 3 Plan A : Write a text file (If only points, load as XY events, export) For lines and polygons : Two files, sample tool to load generate-like file, add attributes.txt, join tables, export. Watch for extra spaces!!! Easier to code, but risks ms-click RSI For a one-off this is convenient enough

Extending Python Step 3 Plan B : Create directly using gp… Delete the last featureclass! Define a projection object (NZTM or NZMG) Create a featureclass (shapefile) Add fields to hold sheet name parts

Extending Python Step 4 Load the sheet rectangles ESRI sample adds layer, but no names Own module adds names but no layer Note names have “/” replaced with “_” to work with MapBook Don’t forget the projection definition What is a projection definition?

Extending Python Review If you can create a text file, then use samples tool for a one-off project. No graphic interaction which means you will have to stay with ArcPlot amls. Projection definitions are obscure. Could not integrate it with MapBook. Could not call sample from another script.

Extending Python Enhancement Requests Upgrade standard install to Python 2.4+ Fix documentation errors and omissions Performance, usability, functionality Add COM error messages More support for Win32 Python Interaction with a map An ArcMap COM interface

Extending Python References The bible for COM interfaces and Python “Python Programming on Win32” - Mark Hammond, O’Reilly Press