CSV library basics in Ruby - Mini Project: Build & Apply

CSV library basics

📖 Scenario: You work in a small bookstore. You have a CSV file listing books and their prices. You want to read this file and find books cheaper than a certain price.

🎯 Goal: Build a Ruby program that reads a CSV file of books and prices, filters books cheaper than a set price, and prints their titles.

📋 What You'll Learn

Use Ruby's CSV library to read data

Create a variable for the price limit

Use a loop to filter books cheaper than the limit

Print the titles of the filtered books

💡 Why This Matters

🌍 Real World

Reading and filtering CSV data is common in many jobs like sales, inventory, and data analysis.

💼 Career

Knowing how to use Ruby's CSV library helps you handle real data files and automate tasks in many programming jobs.

1

Create the CSV data as a string

Create a variable called csv_data and set it to this exact string including newlines: "Title,Price\nRuby Basics,25\nJavaScript Guide,30\nPython Intro,20"

Ruby

# Create a variable called csv_data with the exact CSV string
# Your code here

Need a hint?

Use double quotes and include newline characters \n exactly as shown.

2

Set the price limit

Create a variable called price_limit and set it to the integer 25

Ruby

csv_data = "Title,Price\nRuby Basics,25\nJavaScript Guide,30\nPython Intro,20"
# Create a variable called price_limit and set it to 25
# Your code here

Need a hint?

Just assign the number 25 to price_limit.

3

Parse CSV and filter books cheaper than price_limit

Use require 'csv' to load the CSV library. Then create a variable called cheap_books that uses CSV.parse on csv_data with headers: true. Use .select with a block that keeps rows where the Price converted to integer is less than price_limit. Then map the result to get an array of the Title values.

Ruby

csv_data = "Title,Price\nRuby Basics,25\nJavaScript Guide,30\nPython Intro,20"
price_limit = 25
# Require CSV and create cheap_books array with titles of books cheaper than price_limit
# Your code here

Need a hint?

Use CSV.parse with headers: true, then select rows with price less than price_limit, then map to get titles.

4

Print the titles of cheap books

Write a puts statement to print the cheap_books array.

Ruby

require 'csv'
csv_data = "Title,Price\nRuby Basics,25\nJavaScript Guide,30\nPython Intro,20"
price_limit = 25
cheap_books = CSV.parse(csv_data, headers: true).select { |row| row['Price'].to_i < price_limit }.map { |row| row['Title'] }
# Print the cheap_books array
# Your code here

Need a hint?

Use puts to print the array. It will print each title on its own line.