csv_script.py

import csv
from itertools import groupby

# Constants

TRANSACTIONS_FILE = "transactions.csv"
PRODUCTS_FILE = "products.csv"


def get_city_mapping():
    with open(PRODUCTS_FILE) as file:
        reader = csv.DictReader(file)
        mapping = {}
        for row in reader:
            mapping[row["prod_id"]] = row["city"]
    return mapping


def get_visited_transactions(city_mapping):
    with open(TRANSACTIONS_FILE) as file:
        reader = csv.DictReader(file)
        data = []
        for row in reader:
            product = row["prod_id"]
            city = city_mapping[product]
            visited = int(row["visited"])
            data.append((city, visited))
    return data


def main():
    city_mapping = get_city_mapping()
    data = get_visited_transactions(city_mapping)
    data.sort()
    for city, group in groupby(data, key=lambda row: row[0]):
        visited_data = [row[1] for row in group]
        orders = len(visited_data)
        visited = sum(visited_data)
        percentage = visited / orders * 100
        print(
            f"City {city} had {orders:3d} orders, {visited:3d} visits,"
            f" and a percentage visited of {percentage:5.1f}%"
        )


if __name__ == "__main__":
    main()