Python script in ArcMap to fill a field in a shapefile based on information in other fields

Question

I am trying to fill a field of a shapefile that is delevoped by a number of unions. The content of the field is supposed to inform about the origin of a polygon in the shape.

I am not experienced in python scripts, so my solution is not quite elegant:

def  FillInfo(Info,Info_WB,Info_UESG,Info_GB,Info_Moo,Info_HHS,Info_PT,Info_SN,Info_SA):
return Info_WB + ',' + Info_UESG + ',' + Info_GB + ',' + Info_Moo + ',' + Info_HHS + ',' + Info_PT + ',' + Info_SN + ',' + Info_SA

Info is the field that is supposed to contain the information regarding the origin of the polygon and Info_NN are the fields containing this information.

The problem is, I do not want a row of commas if the fields are empty.

How can I manage to only string together "valid" entries?

Answer 1

def  FillInfo(Info,Info_WB,Info_UESG,Info_GB,Info_Moo,Info_HHS,Info_PT,Info_SN,Info_SA):
    returnItems = [Info_WB,Info_UESG,Info_GB,Info_Moo,Info_HHS,Info_PT,Info_SN,Info_SA]
    returnItemsClean = [i for i in returnItems if i]
    return ','.join(returnItemsClean)

The explanation of what the join method does from the Python docs:

string.join(words[, sep]) Concatenate a list or tuple of words with intervening occurrences of sep. The default value for sep is a single space character. It is always true that string.join(string.split(s, sep), sep) equals s.

Step by step:

1. You add your fields to a list
2. You clean up the list by adding only fields that contain a value
3. You join the list items with a comma (or whatever other separator you want)