计算导入的.csv文件中的多次出现

Question

Starting from a large imported data set, I am trying to identify and print each line corresponding to a city that has at least 2 unique colleges/universities there.

So far (the relevant code):

for line in file:

    fields = line.split(",")
    ID, name, city = fields[0], fields[1], fields[3]
    count = line.count()

if line.count(city) >= 2:
    if line.count(ID) < 2:
    print "ID:", ID, "Name: ", name, "City: ", city

In other words, I want to be able to eliminate 1) any duplicate school listings (by ID - this file has many institutions appearing repeatedly), 2) any cities that do not have two or more institutions there.

Thank you!

Answer 1

dicts come in handy when you want to order data by some key. In your case, nested dicts that first index by city and then by ID should do the trick.

# will hold cities[city][ID] = [ID, name, city]
cities = {}

for line in file:
    fields = lines.split()
    ID, name, city = fields
    cities.setdefault(name, {})[ID] = fields

# 'cities' values are the IDs for that city. make a list if there are at least 2 ids
multi_schooled_cities = [ids_by_city.values() for ids_by_city in cities.values() if len(ids_by_city) >= 2]