4. Working with CSV and JSON files

Quiz: 0/5

In this lesson, we'll learn how to work with two types of files that you might encounter when dealing with data: CSV (Comma Separated Values) and JSON (JavaScript Object Notation). These file formats are used to store and share data, and knowing how to handle them is really useful in programming.

Reading and writing CSV files

A CSV file is a simple text file where each line contains values separated by commas. It's often used to store data like lists, spreadsheets, or tables.

Reading CSV files:

You can read data from a CSV file using the csv.reader() function. This function reads each row and splits the values based on commas.

Example:

import csv

with open('data.csv', 'r') as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)

Writing CSV Files:

You can write data to a CSV file using csv.writer(). It helps you add rows to the file, with each value separated by a comma.

Example:

import csv

data = [["Name", "Age"], ["Alice", 30], ["Bob", 25]]

with open('output.csv', 'w', newline='') as file:
    writer = csv.writer(file)
    writer.writerows(data)

Using DictReader and DictWriter

Instead of dealing with rows as simple lists, sometimes it's easier to work with them as dictionaries (where each value has a corresponding key).

DictReader:

This is useful when you want to read CSV data where each row is represented as a dictionary with column names as keys.

Example:

import csv

with open('data.csv', 'r') as file:
    reader = csv.DictReader(file)
    for row in reader:
        print(row)

DictWriter:

This allows you to write dictionaries to a CSV file, where the dictionary keys correspond to the column headers.

Example:

import csv

data = [{"Name": "Alice", "Age": 30}, {"Name": "Bob", "Age": 25}]

with open('output.csv', 'w', newline='') as file:
    fieldnames = ["Name", "Age"]
    writer = csv.DictWriter(file, fieldnames=fieldnames)
    writer.writeheader()
    writer.writerows(data)

Reading and writing JSON files

A JSON file is a text file that stores data in a structured, human-readable format. It's often used to exchange data between web servers and clients.

Reading JSON files:

Use json.load() to read data from a JSON file and turn it into a Python dictionary.

Example:

import json

with open('data.json', 'r') as file:
    data = json.load(file)
    print(data)

Writing JSON files:

Use json.dump() to write Python data (like dictionaries or lists) into a JSON file.

Example:

import json

data = {"name": "Alice", "age": 30}

with open('output.json', 'w') as file:
    json.dump(data, file)