Getting lists of values from a CSV

Question

I have a function that takes a column title, and a response.body from a urllib GET (I already know the body contains text/csv), and iterates through the data to build a list of values to be returned. My question to the gurus here: have I written this in the cleanest, most efficient way possible? Can you suggest any improvements?

def _get_values_from_csv(self, column_title, response_body):
 """retrieves specified values found in the csv body returned from GET
 @requires: csv
 @param column_title: the name of the column for which we'll build a list of return values.
 @param response_body: the raw GET output, which should contain the csv data
 @return: list of elements from the column specified.
 @note: the return values have duplicates removed. This could pose a problem, if you are looking for duplicates.
 I'm not sure how to deal with that issue."""
 dicts = [row for row in csv.DictReader(response_body.split("\r\n"))]
 results = {}
 for dic in dicts:
 for k, v in dic.iteritems():
 try:
 results[k] = results[k] + [v] #adds elements as list+list
 except: #first time through the iteritems loop.
 results[k] = [v]
 #one potential problem with this technique: handling duplicate rows
 #not sure what to do about it.
 return_list = list(set(results[column_title]))
 return_list.sort()
 return return_list

• rxmnnxfpvg: Tip: Don't use a blanket except, you will catch ALL exceptions rather than the one you want.

Answer 1

Here's a shorter function that does the same thing. It doesn't create lists for the columns you're not interested in.

def _get_values_from_csv(self, column_title, response_body):
 dicts = csv.DictReader(response_body.split("\r\n"))
 return sorted(set(d[column_title] for d in dicts))

• Greg Gauthier: Thanks! This is brilliant! I'm still trying to wrap my head around how to use dictionaries in a comprehension context like this. So this is exactly what I was looking for. :)
• Lennart Regebro: sorted() will return a list, so the list() bit isn't needed.
• Martin Stone: Good point, Lennart -- Edited out.

Answer 2

My suggestions:

def _get_values_from_csv(self, column_title, response_body):
 # collect results in a set to eliminate duplicates
 results = set()
 # iterate the DictReader directly
 for dic in csv.DictReader(response_body.split("\r\n")):
 # only add the single column we are interested in
 results.add(dic[column_title])
 # turn the set into a list and sort it
 return_list = list(results)
 return_list.sort()
 return return_list