Calculating Number Of Occurrences Of Dual Parameter Match In A Csv Appending The Results To Csv

What I need to do is calculate the following: The number of times a person appears in the list (column 8) on dates prior to the date specified in the row with the same t data in co

Solution 1:

very minor change:

import csv
import datetime
import copy
from collections import defaultdict

with open(r"C:\Temp\test2.csv") as i, open(r"C:\Temp\results2.csv", "wb") as o:
    rdr = csv.reader(i)
    wrt = csv.writer(o)

    # data is a dictionary where we will save current and previous data like:
    # {
    #    (George Smith, 15t): [
    #         previous date count when column 7 = 1,
    #         previous date count,
    #         current date count when column 7 = 1,
    #         current date count
    #    ]
    data, currdate = defaultdict(lambda:[0, 0, 0, 0]), None
    for line in rdr:
        date = datetime.datetime.strptime(line[0], '%d/%m/%Y')

        # key of dictionary would be tuple looking like
        # (George Smith, 15t)
        name = (line[7], line[9])

        # if date is changed, we have to put current values into previous
        # by copying part of the list
        #
        #    (George Smith, 15t): [
        #         previous date count when column 7 = 1,
        #         previous date count,
        #         current date count when column 7 = 1,
        #         current date count
        #    ]
        #
        # becomes
        #
        #    (George Smith, 15t): [
        #         current date count when column 7 = 1,
        #         current date count
        #         current date count when column 7 = 1,
        #         current date count
        #    ]
        # and then we change currdate variable to current one

        if date != currdate or not currdate:
            for v in data.itervalues(): v[:2] = v[2:]
            currdate = date

        # writing current line + first 2 elements from list (previous counts)
        wrt.writerow(line + data[name][:2])

        # updating current counts
        data[name][3] += 1
        if line[6] == "1": data[name][2] += 1