If else statement

[JamesSmith7]

I am modifying a script suggested in a prior thread.  http://forums.arcgis.com/threads/90242-Polygon-Centroid?highlight=jsmith0705

I want to be able to select a line, determine if the ARCLENGTH field has a value greater than zero, return that value if greater than zero, if not return the value from the Shape_Length field.

The script runs with no errors or results. 

import arcpy  mxd = arcpy.mapping.MapDocument ("CURRENT") df = arcpy.mapping.ListDataFrames (mxd)[0]  lyr = arcpy.mapping.ListLayers(mxd, "Lot_Lines", df)[0]  for lyr in arcpy.mapping.ListLayers(mxd):  tlyr = lyr  dsc = arcpy.Describe(tlyr)  sel_set = dsc.FIDSet  if dsc.shapeType == "Line":   if len(sel_set) > 0: #If ARCLENGTH value > 0           arcpy.AddMessage(str(ARCLENGTH)) #Return ARCLENGTH value   else:    arcpy.AddMessage(str(Shape_Length)) #Return Shape_Length value

[JacobDrvar]

James:

Can you create a feature class with a small subset of features (say 10) and then print out the fidset?

It appears from Richard's last post that the semi-colon delimited string will need to be converted to a comma separated list.  You shouldbe able to find python methods to easily perform that process.

print "Data type: " +dsc.dataType
Data type: FeatureLayer
print "File path: " + dsc.path
File path: C:\User\County\Personalworkspace.gdb
print "Catalog path: " + dsc.catalogpath
Catalog path: C:\User\County\Personalworkspace.gdb\Lot_Lines
print "File name: " +dsc.file
File name: Lot_Lines
print "Base name: " + dsc.baseName
Base name: Lot_Lines
print "Name: " + dsc.name
Name: Lot_Lines
print dsc.shapeType
Polyline

Those all work, but when trying to run: print dsc.FidSet, no results are returned.  Is that what you were meaning, Michael?

I am now going to work on creating the comma separated list.

[JamesSmith7]

James:

Can you create a feature class with a small subset of features (say 10) and then print out the fidset?

It appears from Richard's last post that the semi-colon delimited string will need to be converted to a comma separated list.  You shouldbe able to find python methods to easily perform that process.

print "Data type: " +dsc.dataType
Data type: FeatureLayer
print "File path: " + dsc.path
File path: C:\User\County\Personalworkspace.gdb
print "Catalog path: " + dsc.catalogpath
Catalog path: C:\User\County\Personalworkspace.gdb\Lot_Lines
print "File name: " +dsc.file
File name: Lot_Lines
print "Base name: " + dsc.baseName
Base name: Lot_Lines
print "Name: " + dsc.name
Name: Lot_Lines
print dsc.shapeType
Polyline

Those all work, but when trying to run: print dsc.FidSet, no results are returned. Is that what you were meaning, Michael?

I am now going to work on creating the comma separated list.

[JakeSkinner]

Python is case sensitive.  Try dsc.fidSet

[JamesSmith7]

Python is case sensitive.  Try dsc.fidSet

The result is the same whether I use dsc.fidSet, dsc.FidSet, or dsc.FIDSet.

[JakeSkinner]

Attached is some data you can test with.  Add the feature class to ArcMap, select a single line, then execute the following:

mxd = arcpy.mapping.MapDocument("CURRENT")
for lyr in arcpy.mapping.ListLayers(mxd):
    dsc = arcpy.Describe(lyr)
    sel_set = dsc.fidSet
    if dsc.shapeType == "Polyline":
        rows = arcpy.SearchCursor(lyr, "OBJECTID = " + sel_set)
        for row in rows:
            arcLength = row.ARCLENGTH
            shapeLength = row.shape.length
        if arcLength > 0:
            print arcLength
        else:
            print shapeLength
    del row, rows

[RichardFairhurst]

The result is the same whether I use dsc.fidSet, dsc.FidSet, or dsc.FIDSet.

Are you positive your layer has a feature selection already applied?  If nothing is selected, no FID values should be returned.

[JamesSmith7]

Attached is some data you can test with.  Add the feature class to ArcMap, select a single line, then execute the following:

mxd = arcpy.mapping.MapDocument("CURRENT")
for lyr in arcpy.mapping.ListLayers(mxd):
    dsc = arcpy.Describe(lyr)
    sel_set = dsc.fidSet
    if dsc.shapeType == "Polyline":
        rows = arcpy.SearchCursor(lyr, "OBJECTID = " + sel_set)
        for row in rows:
            arcLength = row.ARCLENGTH
            shapeLength = row.shape.length
        if arcLength > 0:
            print arcLength
        else:
            print shapeLength
    del row, rows

Jake, the script works with the feature class you provided, using the Python window within ArcMap.

[JamesSmith7]

Are you positive your layer has a feature selection already applied?  If nothing is selected, no FID values should be returned.

Richard,

I am using the select by rectangle to select one Polyline before running the script.

[RichardFairhurst]

Jake, the script works with the feature class you provided, using the Python window within ArcMap.

Yes, but it only worked because you selected one feature.  If you select 2 features you will get nothing.  That is why you have to use the IN operator to work with a list of 0 or more items.

OBJECTID = 12345; 12346

is an invalid selection statement (not sure how Python resolves the list into the SQL statement, but = cannot be used with a list).

OBJECTID IN (12345, 12346)

is valid and will return both records.

OBJECTID IN (12345; 12346)

Returns nothing since a semicolon is invalid in an SQL list.

[JakeSkinner]

Can you export a small portion of the feature class you are using, zip it, and upload it here?