Question

Part 1 Lottery Statistics

Create a program that will compute some statistics on winning lottery numbers.

• Download a .csv file from Winning Powerball Numbers containing a record of past winning numbers.
• Examine the formatting of this file.
• Create a dictionary that contains each winning number and the number of times that number was drawn.
• Print the 10 most frequently drawn numbers, and the 10 least frequently drawn numbers. HINT: You can’t sort a dictionary. Build a list that is ordered by frequency.
• The output may look something like the following. (The output below is not correct for your file.)

The 10 most frequent numbers are:
55 was drawn 89 times.
66 was drawn 83 times.
...
77 was drawn 71 times.
The 10 least frequent numbers are:
11 was drawn 14 times.
22 was drawn 18 times.
...
33 was drawn 26 times.

Answer 1

For the test file i have downloaded the powerball winning numbers in csv format from : https://catalog.data.gov/dataset/lottery-powerball-winning-numbers-beginning-2010

code is in python 3.7, all details have been mentioned in comments

import csv
import operator

with open('powerball_2010.csv') as csv_file:

    # converting the csv to dictionary rows
    csv_reader = csv.DictReader(csv_file)

    # to store the frequency / hash
    winning_dict = {}

    for row in csv_reader:
        # in the csv file the winning row consisits of a sequence of space separated numbers, so we first split by space and cast each string as integer
        # then for each integer we check if the value is already present in the dictionary or not and increment its frequency count
        winning_numbers = [int(i) for i in row['Winning Numbers'].split(' ')]
        for number in winning_numbers:
            if number in winning_dict:
                winning_dict[number] += 1
            else:
                winning_dict[number] = 1

    # sorting by frequency, each element is a tuple (key,frequency)
    sorted_by_frequency = sorted(winning_dict.items(), key=operator.itemgetter(1))

    # print(sorted_by_frequency)

    # get last 10 elements from array
    most_frequent_10 = sorted_by_frequency[-10:]
    # get first 10 elements from array
    least_frequent_10 = sorted_by_frequency[:10]

    print("The 10 most frequent numbers are: ")
    for element in reversed(most_frequent_10):
        print("{} was drawn {} times".format(element[0], element[1]))

    print("\n\nThe 10 least frequent numbers are: ")
    for element in least_frequent_10:
        print("{} was drawn {} times".format(element[0], element[1]))

Output: