Keeping Empty ShapeFiles?

[AaronChristiansen]

Hello All,

I am trying to create a tool in python that can potentially find areas of wind turbines by county. I have the correct process down, but in some counties there are parameters that don't exist. So for example I take into account airports, hydrology, slope, roads, urban areas, and more. But what if an area does not have that parameter ie. no military zones in some counties. But I have a code that requires the military area. Is there a way to use the tool so that it can ignore certain parameters when there is no data? Below is the piece of code that is giving me issues. I would still like to use this code, but I need it to work when there is no data in some of the shape files. I feel there is a way to do this without having to write a ton of if-then blocks. 

Thanks in advance!

arcpy.analysis.Union([Airports, Native, Parks, BufRail, Urban, BufRoads, Forests, Military, BufStreams, BufWaterBodies], Workings+"Avoid.shp", "ALL", None, "GAPS")‍

-Aaron

[AdrianWelsh]

Aaron,

This thread might be best placed in the Python‌ place.

Would it be acceptable to have null values in your code and/or attributes?

[AaronChristiansen]

Hey Adrian, 

Thank you for your feedback. Null values are fine for this analysis.

[XanderBakker]

How do you specify the input for the tool? Is each layer a separate parameter or do you let the user select a list of featureclasses with a single control?

[AaronChristiansen]

So each input has been specified in precursor code using a gui and each layer is a separate parameter.

[XanderBakker]

If each has it's own variable, you can validate to see if it is empty and exclude it from the list. Look at the snippet below:

Airports = r'blah 1'
Native = r'blah 2'
Parks = None  # not sure if it will be an empty string or null
BufRail = r'blah 4'
Urban = r'blah 5'
BufRoads = ''  # not sure if it will be an empty string or null
Forests = r'blah 6'
Military = r'blah 7'
BufStreams = None  # not sure if it will be an empty string or null
BufWaterBodies = r'blah 8'

lst = [Airports, Native, Parks, BufRail, Urban, BufRoads, Forests, Military, BufStreams, BufWaterBodies]

new_lst1 = [a for a in lst if a != '']
new_lst2 = [a for a in lst if a != None]
new_lst3 = [a for a in lst if a != None and a != '']

print lst
print new_lst1
print new_lst2
print new_lst3
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This will yield:

['blah 1', 'blah 2', None, 'blah 4', 'blah 5', '', 'blah 6', 'blah 7', None, 'blah 8']
['blah 1', 'blah 2', None, 'blah 4', 'blah 5', 'blah 6', 'blah 7', None, 'blah 8']
['blah 1', 'blah 2', 'blah 4', 'blah 5', '', 'blah 6', 'blah 7', 'blah 8']
['blah 1', 'blah 2', 'blah 4', 'blah 5', 'blah 6', 'blah 7', 'blah 8']‍‍‍‍

Use the new list in the Union:

arcpy.analysis.Union(new_lst3, Workings+"Avoid.shp", "ALL", None, "GAPS")‍

You will probably have to check to see if the list has at least 2 items to avoid problems.

[AaronChristiansen]

Thank you so much!

This will definitely help me!

Best,

Aaron