Python how to separate different values in same column in csv file?

Question

I have a csv file that looks like this: csv file

Essentially I'm trying to add each value in column E (political regime) to a list of lists, separated by the country name in column B.

So, every time Afghanistan appears, add its political regime value to a list, then when a new country appears, add those values to another list.

I also have to do this task WITHOUT pandas or numpy.

I hope this makes enough sense but here's my current code which is an infinite loop and freezes my program.

def read_file(fp):


reader = csv.reader(fp)
next(reader, None)
country_names = []
list_of_regime_lists = []
for line in reader:
    country_names.append(line[1])
for line in reader:
    line[4]=int(line[4])

return country_names, list_of_regime_lists

Answer 1

This is a good use case for a dictionary.

def read_file(fp):
    with open(fp, 'r') as file:
        contents = file.readlines()
    regimes = {}
    for row in contents[1:]:  # skip header row
        fields = row.split(',')
        country = fields[1]  # column B
        regime = fields[4]   # column E
        if country not in regimes:  # check if this is a new country
            regimes[country] = [regime]  # start a new list of regimes
            # regimes[country] = {regime}  # alternatively use a set to ignore duplicate regimes
        else:
            regimes[country].append(regime)  # or add the regime to that country's list
            # regimes[country].add(regime)  # if using a set
    return regimes