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I have attached my stream order network image. I have five different order streams. There are several segments in each order. Now my problem is to select one segment of stream at a time for the further processing. I think this is not a big problem. But I am in trouble, I m using ArcGIS 10 and Python for processing. It would be great if you give some guidance to select each segment of stream at a time using python and GIS10.

enter image description here

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Can you define 'segment of stream'? Are you trying to use segment like it is used in geometry (i.e a connected path between two endpoints) Or do you mean feature? – Devdatta Tengshe Jun 21 '13 at 9:35
Are you able to post some of your current code so that we can see the direction you are heading in, please? – PolyGeo Jun 21 '13 at 9:45
In my case, Segment of Stream means...starting point till the intersection point to another stream. In this case there are several 1,2,3,4 order stream segments and only one 5th order stream segement. I want to get like one segment from the origin till the confluence to another stream. – Ja Geo Jun 21 '13 at 11:46
Do you have one seg. per order or multiple seg. per order? – artwork21 Jun 21 '13 at 11:53
I have multiple segments in one order. In this case I have more segments in 1-4 order and only one in 5th order – Ja Geo Jun 21 '13 at 12:11

It looks like your river network is derived from a flow direction grid? Have a look at this tool as it creates unique link IDs from your RASTER network.

Have you seen RivEX a VECTOR network processing tool? It can computer Strahler order from a vector network and assign the segment ID's you require.

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I'm not sure what your "further processing" involves, however the general idea for iterating through each segment follows these steps:

  1. convert your feature class to a feature layer
  2. define a cursor to loop through your feature table
  3. define the column to get values from
  4. assign value to a variable and use that variable inside your select layer by attribute method/expression
  5. do "further processing"
  6. keep looping...
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