Re: [Tutor] ArcGIS Create a python script to generate north-facing aspect raster from digital elevation model

[P McCombs]

On Mar 21, 2015 1:22 AM, Michael Omohundro
momohund1...@yahoo.com.dmarc.invalid wrote:

 Does anyone know how to create a python script to generate an aspect
raster from the input elevation in a digital elevation model?

This topic is out of the normal scope of the mailing list. It's hard to say
if you are having a python issue or an ArcGIS issue.

I could possibly help with the latter,  but please provide the trace back
you get when it errors out,  or how the output differs from what you
expect.

Without the data you are using I'm not going to attempt to run your code.


 I need to specify TWO variables as user parameters: input elevation and
output north-facing aspect.
 I need to create an aspect raster from the input elevation from a digital
elevation model.
 I need to find the north facing aspect is the trick, between 0 and 22.5
and between 337.5 – 360. These are the north facing elevation ranges.
 I need to reclass the north facing aspect into a 1/Nodata raster.
 Any cell is north facing should have value 0, other cells should be
NoData.
 I need to save the results as a permanent raster named as my second input
parameter.
 I can't use ModelBuilder then convert it into Python script.

 Here is what I have so far:


 # Created on: March 20 2015
 # Usage: lab03-5 Aspect from raster surface
 # Requirements: ArcGIS Desktop and Spatial Analyst Extension
 #
---

 # Import system modules
 import arcpy
 from arcpy import env
 from arcpy.sa import *
In my experience this makes debugging harder, I can't tell if you are using
local functions or module functions without a detailed knowledge of the
module you imported.

 arcpy.env.overwriteOutput = True

 # Set environment settings.  dem30 is the digital elevation model that
holds the elevation data.
 elevation =
rF:\NW_Missouri_State_University\_Python_Class\Week_10\lab10\dem30

 # North facing elevation 1, range 0 to 22.5
 inRange_North1 = range (0, 22.5, 0.5)
 #North facing elevation 2,range 337.5 - 360
 inRange_North2 = range (337.5, 360, 0.5)

 # Set local variables
 inRaster = elevation

 # Check out the ArcGIS Spatial Analyst extension license
 arcpy.CheckOutExtension(Spatial)

 # Execute Aspect
 outAspect = Aspect(inRaster)

 # Save the output

outAspect.save(F:\NW_Missouri_State_University\_Python_Class\Week_10\lab10\TestLab10_5)

 # Specify the current workspace as the workspace where the input
elevation raster is.
 # Extract the base name of the elevation raster.
 arcpy.env.workspace = os.path.dirname(elevation)
 inputElev = os.path.basename(elevation)

 # Specify the output raster name as the input elevation name appending
with “NorthFacing”.
 saveReclass = arcpy.env.workspace + os.sep + inputElev + NorthFacing

 # Check out the Spatial Analyst extension license for the script.
 arcpy.CheckOutExtension(Spatial)

 # Construct a map algebra expression to find the cell with elevation
equal to the range values.
 minRaster = arcpy.sa.Raster(inputElev) = inRange_North1
 maxRaster = arcpy.sa.Raster(inputElev) = inRange_North2

 # Construct a map algebra expression to perform a Boolean And
 # operation on the cell values of minRaster and maxRaster.
 # If the cell value is 1 in both raster, then set the output cell value
as 1.
 # Otherwise, set the output cell value as 0. Save the output raster as
variable outRaster.
 outRaster = minRaster  maxRaster

 # Create a remap object through RemapValue() function.
 # If the old value is 0, then set the new value as NODATA.
 # If the old value is 1, then set the new value as 1.

 remap = arcpy.sa.RemapValue([[0, NODATA], [1, 1]])
 outReclassify = arcpy.sa.Reclassify(
 outRaster, Value, remap, NODATA)

 #Call the save method on the raster object to save the raster as
permanent dataset.
 outReclassify.save(saveReclass)

 # Check in the Spatial Analyst extension license.
 arcpy.CheckInExtension(Spatial)

I'm guessing that you've resolved this problem in the past week,  but for
future problems I encourage you to check what data types are expected for
the functions you are calling. They can be unexpected sometimes in arcpy.

Paul McCombs
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Re: [Tutor] Exercise to work on

[P McCombs]

On Aug 12, 2014 3:29 PM, keith papa keith...@live.com wrote:

 Hi, am a newbie to python and I wondering if you guys can give me some
exercise to work on. I have learned: print function , if function ,
strings, variables, and raw_input. The more the better

Checkio.org is a game made of python coding challenges. They start simple,
demonstrate functional testing, and provide other users' solutions.

http://www.checkio.org
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Re: [Tutor] Need help with python script

[P McCombs]

Sorry, I missed copying this to the list.

On Aug 4, 2014 8:13 AM, P McCombs mcco...@imperium.org wrote:


 On Jul 31, 2014 4:50 PM, McKinley, Brett D. bmckin...@mawss.com wrote:
 
  I would like to see if someone can help me with a python script.  I’m
trying to export a file geodatabase feature class to csv file.  This is
what I have so far:

 Does the code you attached execute successfully?
 Are you running this as a tool,  or from the command line?
 Be cautioned that arcpy is outside the scope of this mailing list,  but
it won't have much to do with your questions at first.

 
 
  import arcpy
 
  import os
 
  import csv
 
  import domainvalues
 
 
 
 
 
  def export_to_csv(dataset, output, dialect):
 
  Output the data to a CSV file
 
  # create the output writer
 
  out_writer = csv.writer(open(output, 'wb'), dialect=dialect)
 
  # return the list of field names and field values
 
  header, rows = domainvalues.header_and_iterator(dataset)
 
 
 
  # write the field names and values to the csv file
 
  out_writer.writerow(map(domainvalues._encodeHeader, header))
 
  for row in rows:
 
  out_writer.writerow(map(domainvalues._encode, row))
 
 
 
  if __name__ == __main__:
 
  # Get parameters
 
  dataset_name = arcpy.GetParameterAsText(0)
 
  output_file = arcpy.GetParameterAsText(1)
 
  delim = arcpy.GetParameterAsText(2).lower()
 
  dialect = 'excel'
 
  if delim == 'comma':
 
  pass
 
  else:
 
  dialect = 'excel-tab'
 
  try:
 
  export_to_csv(dataset_name, output_file, dialect)
 
  except Exception as err:
 
  arcpy.AddError('Error: {0}'.format(err))
 
 
 
 
 
  I would like for the script to export only certain fields and also
export only the newest records.  As for now, it’s exporting everything.
 

 It is best to try to add one new feature on your own and attach the
result. You will get the best feedback that way.

 
 
  Thanks
 
  Brett McKinley
 
 
 
 
 
 
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[Tutor] How to create web interface?

[P McCombs]

On May 14, Danny Yoo wrote:
  Another option might be to turn your program into a web site, so that
  the interface is the web browser, which everyone is getting used to
  these days.  But this, too, is also... involved.  :P

I have a little volunteer scheduling application I've written as a
module, with about a dozen functions, that reads and writes to a
Sqlite database. I'd like to run a web server on my machine just for
my local use.

I don't understand how precisely the web page would communicate with
the python program.

If anyone has a suggestion on specific modules, and tutorials to use
to create a web interface for a python program, I'd love to hear it.

I'm using python 2.7 on OSX Mavericks.
I'm fairly new to python. I have some experience with apache, and php,
I comfortable with HTML.

I'm also happy to know where a better forum for this question would be.

Thank you, Paul McCombs
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Re: [Tutor] How to create web interface?

[P McCombs]

Thank you all for your responses. This is exactly the information I
was looking for.

Paul McCombs

On Tue, May 20, 2014 at 4:36 PM, Alan Gauld alan.ga...@btinternet.com wrote:
 On 20/05/14 21:00, P McCombs wrote:

 On May 14, Danny Yoo wrote:

 Another option might be to turn your program into a web site, so that
 the interface is the web browser, which everyone is getting used to
 these days.  But this, too, is also... involved.  :P


 I have a little volunteer scheduling application I've written as a
 module, with about a dozen functions, that reads and writes to a
 Sqlite database. I'd like to run a web server on my machine just for
 my local use.

 I don't understand how precisely the web page would communicate with
 the python program.


 If you want to understand the basics then the cgi module in the standard lib
 is a good starting point. It makes life a bit
 easier than nothing but exposes the underlying technology.

 But if you want something to keep you sane and make web
 programming easy then Pyhon has more web frameworks than
 you can shake a stick at. From very simple (Flask, CherryPy)
 to very complex (Django, Zope).

 There is a good page on the python.org web site that summarises
 the technology and many of the most popular frameworks but
 ultimately you just pick one and work through its tutorial.

 Start here for theory:

 https://docs.python.org/3/howto/webservers.html

 and go here for the list:

 https://wiki.python.org/moin/WebFrameworks


 HTH
 --
 Alan G
 Author of the Learn to Program web site
 http://www.alan-g.me.uk/
 http://www.flickr.com/photos/alangauldphotos


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