How to use for loop to add and calculate new field?

Question

I am trying to use for loop to add and calculate a newfield for 2 shapefiles and a different new field for 2 other shapefiles. When I tried to do these 2 loops as one, it did not work so I separated them into 2 loops and it worked. I am using python 2.7 stand alone (arcmap 10.2).

more details: So I want to make a new field and add 'CA' to shapefiles containing _CA.shp (*_CA.shp). I also want to make a new field and add 'AZ' to shapefiles containing _AZ.shp (*_CA.shp). When I created a loop (the first code), I got my roads_CA and railroads_CA to work but roads_AZ and railroads_AZ did not create a new field containing 'AZ'. I did not get an error which means the loop ran through but I guess the elif came out false so it did not create anything.

here is my code:

 CAshp = arcpy.ListFiles("*_CA.shp")
 for CA in CAshp:
 if (CAshp == 'roads_CA.shp', CAshp == 'railroads_CA.shp'):
 newField = 'StateAbbre'
 arcpy.AddField_management(CA, newField, 'TEXT')
 arcpy.CalculateField_management(CA, newField, "'CA'", "PYTHON_9.3")
 elif (CAshp != 'roads_AZ.shp', CAshp != 'railroads_AZ.shp'):
 AZshp = CAshp.extend(arcpy.ListFiles("*_AZ.shp"))
 newField = 'StateAbbre'
 arcpy.AddField_management(AZshp, newField, 'TEXT')
 arcpy.CalculateField_management(AZshp, newField, "'AZ'", "PYTHON_9.3") 

• BradHards: Welcome to gis.SE. You look like you're using arcpy in here - can you add details of which version to the question (just click edit below the question)? Also, can you fix the formatting on your code so the whitespace matches what you are really using?
• gm70560: It looks as if the one loop method only has ".CA.shp"'s and no ".AZ.shp"'s returned from ListFiles.
• Trey: Yes, that is what I am having with when I make one loop. CA.shp will work but when it gets to the AZ part is said error executing. I notices that if I replace AZshp, from the AddField and CalculateField, with CA the whole loop will work, but that would mean my stateAbbrev for AZ would be CA and not AZ. This is why I made 2 loops because it worked that, but I want to see if it is possible to make 1 loop.
• PolyGeo: You seem to have had some advice and provided more details as Comments, but do not yet seem ready to Accept an Answer, so I recommend that you revise your Question using its edit button to try and make it clearer.

Answer 1

Try extending the list of files; the elif isn't finding any AZ's since [CAshp] only has CA's from "*CA.shp".

CAshp = arcpy.ListFiles("*_CA.shp")
CAshp.extend(arcpy.ListFiles("*_AZ.shp")
for CA in CAshp: 
 if CA == 'roads_CA.shp' or CA == 'railroads_CA.shp':
 arcpy.AddField_management(CA, 'StateAbbre', 'TEXT')
 arcpy.CalculateField_management(CA, newField, "'CA'", "PYTHON_9.3")
 elif CA == 'roads_AZ.shp' or CA == 'railroads_AZ.shp':
 arcpy.AddField_management(CA, 'StateAbbre', 'TEXT')
 arcpy.CalculateField_management(AZshp, newField, "'AZ'", "PYTHON_9.3")

for clarity, maybe I should have renamed the varibles:

# add CA's and then extend list with AZ's
shapes = arcpy.ListFiles("*_CA.shp")
shapes.extend(arcpy.ListFiles("*_AZ.shp")
for shp in shapes: 
 # first part of the loop for CA's
 if shp == 'roads_CA.shp' or shp == 'railroads_CA.shp':
 arcpy.AddField_management(shp, 'StateAbbre', 'TEXT')
 arcpy.CalculateField_management(shp, newField, "'CA'", "PYTHON_9.3")
 # second part of the loop for AZ's
 elif shp == 'roads_AZ.shp' or shp == 'railroads_AZ.shp':
 arcpy.AddField_management(shp, 'StateAbbre', 'TEXT')
 arcpy.CalculateField_management(shp, newField, "'AZ'", "PYTHON_9.3")

• Trey: I ran your code and it came out an error: arcpy.CalculateField_management(AZshp, newField, "'AZ'", "PYTHON_9.3") NameError: name 'AZshp' is not defined
• Trey: I then gave it a name AZshp = CAshp.extend(arcpy>ListFiles("*_AZ.shp") but I still got the same error.
• Trey: But if I change AZshp with CA, it will create a new field and add 'AZ' to the *_CA.shp shapefile. For the elif, I want it to create a new field containing AZ for *AZ.shp.