Selecting columns from CSV file

Python newbie here.

I have a bunch of CSV files of stock prices. They are structured as date, opening, high, low, close, adj. close, volume. I only need the date (column 1), the opening (column 2) and close (column 5).

The task prohibits the use of pandas. How can I extract those three columns and return them?

This is my attempt, but that doesn’t extract the 3 columns I need.

def read_daily_prices(daily_price):
    daily_prices = []
    with open(stocks_symbols + ".csv", "r", newline='') as csvfile:
        csvreader = csv.DictReader(csvfile, delimiter=',')
            for daily_price in csvreader:
                daily_prices.append(daily_price)

Answer

Hi👋🏻 Hope you are doing well!

If I understood your question correctly, you can do something like that:

import csv

path = "stocks.csv"
# stocks.csv
# date, opening, high, low, close, adj_close, volume
# 2022-01-01, opening_1, high_1, low_1, close_1, adj_close_1, volume_1
# 2022-01-02, opening_2, high_2, low_2, close_2, adj_close_2, volume_2

columns = ["date", "opening", "close"]

daily_prices = []

with open(path, newline="") as csvfile:
    reader = csv.DictReader(csvfile, delimiter=",")
    for row in reader:
        daily_prices.append([row["date"], row["opening"], row["close"]])

print(daily_prices)
# [['2022-01-01', 'opening_1', 'close_1'], ['2022-01-02', 'opening_2', 'close_2']]

daily_prices_dicts = [dict(zip(columns, row)) for row in daily_prices]

print(daily_prices_dicts)
# [{'date': '2022-01-01', 'opening': 'opening_1', 'close': 'close_1'}, {'date': '2022-01-02', 'opening': 'opening_2', 'close': 'close_2'}]

the main idea is: csv.DictReader returns list of dicts so you can select necessary columns by key. 🙂