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i want to extract a rectangle corner coordinates of a shape file in python script..please suggest me a solution.

Thanks in advance, Bhavya

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2 Answers

A lot depends on what APIs you have installed. Since you haven't tagged this post as 'ArcGIS' or 'ESRI', I assume you are not using ArcPy. Probably the most common Python GIS APIs is OGR. In OGR do this:

import ogr
ds = ogr.Open(r"C:\some_folder\my_subfolder\myShapefile.shp")
lyr = ds.GetLayer(0)

This gives the extent of the entire shapefile. To get the extent of individual features you must drill down and get their envelopes.

PS: I should have said that the above code give you the extent as (xMin, xMax, yMin, yMax)

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Hi Sylvester Sneekly, for above code i got the following error..Traceback (most recent call last): File "C:/Documents and Settings/vamsi/.qgis/python/plugins\Transform\dlgTransform.py", line 80, in GetExtent print(lyr.GetExtent()) IOError: [Errno 9] Bad file descriptor........please help..thanks –  vamsi Apr 4 '12 at 7:00
That's a very odd error to get here. Are you diverting the stdout to a file? BTW I only suggested to print the extent to screen as a quick demo. You could store it in a file for consumption later in your program instead e.g. "myExtent = lyr.GetExtent()" –  MappaGnosis Apr 4 '12 at 16:31
Thank u so much Sylvester for the answer –  vamsi Apr 5 '12 at 4:26
Hi.. Sylvester Sneekly, how can i add the extent values into existing fields like llx,lly lrx lry ulx uly urx ury –  vamsi Apr 7 '12 at 7:24
You need this tutorial: gis.usu.edu/~chrisg/python/2009. It is excellent and will really get you going with GDAL/OGR. –  MappaGnosis Apr 7 '12 at 19:42
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I'm assuming you have ArcGIS. There is a very good worked example at http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Dataset_properties/000v0000002m000000/

Otherwise a common python library for geo-related tasks is Shapely. However, I think you might have more luck with OGR/GDAL. There is a tutorial here, including how to get the extent (see page 18)

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Hi Stev, i have QGis and want to develope python plugins to QGis..i referred the tutorial u suggested. But i dint get the statement "os.chdir('f:/data/classes/python/data')" please clarify..Thanks for your reply :) –  vamsi Apr 3 '12 at 10:42
If you just want to know the extent in QGIS go to the layer properties and look at the Metadata tab. –  MappaGnosis Apr 3 '12 at 10:51
Hi..Sylvester Sneekly, thanks for your answer and i got the extent..but i want it by using the python script.. –  vamsi Apr 3 '12 at 11:00
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