Question

I’ve got a CSV with agency names and addresses. If I want a string of agency names with the same address (specifically the same zip code), how can I do that in R or Python? Whichever way is most efficient is preferable, but I’m still learning both. Google Refine gave me the counts of each zip code cluster already, but I just need to know which agencies correspond to those zips.

PS. Yes I know zip code isn’t good to rely upon; the point of this is to illustrate that.

Example input data:

Final output (to be merged with shapefiles later):

Answer 1

You should be able to just construct a dictionary:

import csv

from collections import defaultdict

agencies = defaultdict(list)

with open('file.csv', 'r') as handle:
    reader = csv.reader(handle)

    for row in reader:
        agencies[row[2]].append(row[0])

Now, agencies contains a mapping of zip codes to agencies.