[GIS] Concatenating fields with label expressions using Python

arcgis-10.2arcgis-desktoplabelingpython

I am trying to combine three numeric fields together for a feature's label. I only want to label the feature if it is over 0. The labeled numbers need to be separated a dash ("-"). This is what I attempted to use as the label expression in ArcMap 10.2:

def FindLabel ( [a1], [a2], [a3] ):
    if ([a3]) == 0 and int([a2]) == 0 and ([a1]) == 0:
        label = " "
    elif ([a3]) == 0 and int([a2]) == 0
        label = [a1]
    elif ([a3]) == 0
        label = [a1] + "-" + [a2]
    else:
        label = [a1] + "-" + [a2] + "-" + [a3]
    return label

Best Answer

This function doesn't need to be too complex. Convert the items you want into a list, then join the result.

def FindLabel([A1], [A2], [A3]):
    args = [A1, A2, A3]
    items = [str(x) for x in args if bool(x) and int(x) > 0]
    if any(items):
        return '-'.join(items)
    else:
        return ' '

If this were proper Python, you would normally use *args to accept any number of arguments into a list.

Related Solutions

[GIS] Using Python in the field calculator – if/else over multiple fields

Try this (edited per @alpha-beta-soup comment):

def myFunction (inter, prop, patch, shp, nat, edge):
    myList = [inter, prop, patch, shp, nat, edge]
    myList.sort()
    myDict = {'Interconnectivity' : inter,
              'PropCover' : prop,
              'PatchSize' : patch,
              'ShapeIndex': shp,
              'Naturalness' : nat,
              'EdgeNat' : edge}

    myVal = 101   # using 101 as a max + 1 possible value; adjust if needed
    myReturn = ''
    for k, v in myDict.iteritems():
        if v < myVal:
            myVal = v
            myReturn = k

    return myReturn

Note that if you have two matching low values, there's nothing to select one over the other. That would require additional checking based on whatever your criteria is. Since a dictionary is unordered, you can't control it that way.

Here's another way without dictionaries, with an optional clause for ties. You may want different logic in case of ties.

def myFunction2 (inter, prop, patch, shp, nat, edge):
    # use tuples to ensure value order
    myScoreTuple = (prop, patch, shp, nat, edge)
    myTextTuple = ('PropCover',
                   'PatchSize',
                   'ShapeIndex',
                   'Naturalness',
                   'EdgeNat')

    # initialize values
    myLowValue = inter
    myReturn = 'Interconnectivity'

    # now check for any lower value
    for i in range(len(myScoreTuple)):
        if myScoreTuple[i] < myLowValue:
            myLowValue = myScoreTuple[i]
            myReturn = myTextTuple[i]

        # optional - add multiple text values in case of tie. Remove if unneeded
        elif myScoreTuple[i] == myLowValue:
            myReturn = ', '.join((myReturn, myTextTuple[i]))

    return myReturn

ArcGIS – Using a Loop in a Python Expression to Stack Labels While Avoiding Zero Value Attributes

You can use List comprehension with an if statement and then join the list elements together to a string with newline in between:

def FindLabel ( [Test1],[Test2],[Test3] ):
  values = [Test1],[Test2],[Test3]
  date = "05/10/2018"
  labellist = ["{0} - {1}".format(date, value) for value in values if value != '0']
  label = "\n".join(labellist)
  return label

Best Answer

Related Solutions

[GIS] Using Python in the field calculator – if/else over multiple fields

ArcGIS – Using a Loop in a Python Expression to Stack Labels While Avoiding Zero Value Attributes

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