242 – Read custom objects from CSV

Say you have a CSV file with sales represented by item names, quantity sold, and price:

Item 1,15,19.99
Item 2,102,9.99
Item 3,5,127

Suppose the data above is in a file sales.csv and now model each row as a dataclass:

from dataclasses import dataclass

@dataclass
class Sale:
    item: str
    quantity: int
    price: float

With the implementation of the dataclass, you can iterate directly over sales objects by building instances of Sale as the data is read from the CSV file:

import csv
from itertools import starmap

with open("sales.csv", "r") as f:
    reader = csv.reader(f)
    for sale in starmap(Sale, reader):
        print(sale)
# Sale(item='Item 1', quantity='15', price='19.99')
# Sale(item='Item 2', quantity='102', price='9.99')
# Sale(item='Item 3', quantity='5', price='127')