Working with Files

Introduction

• Programs often need to save or read data from files. Python makes this simple!
• You can work with text files, CSV files, JSON files, and more.

Reading Text Files

• “`python
• # Read entire file
• file = open('data.txt', 'r') # 'r' means read mode
• content = file.read()
• print(content)
• file.close()
• “`
• Better way (automatically closes file):
• “`python
• with open('data.txt', 'r') as file:
• content = file.read()
• print(content)
• “`

Writing to Files

• “`python
• with open('output.txt', 'w') as file: # 'w' means write mode
• file.write('Hello, World!n')
• file.write('Python is awesome!')
• “`
• Append to Existing File:
• “`python
• with open('output.txt', 'a') as file: # 'a' means append
• file.write('nAdding new line')
• “`

Working with CSV Files

• CSV (Comma Separated Values) files are common for storing data:
• “`python
• import csv
• # Reading CSV
• with open('students.csv', 'r') as file:
• reader = csv.reader(file)
• for row in reader:
• print(row)
• # Writing CSV
• with open('output.csv', 'w', newline='') as file:
• writer = csv.writer(file)
• writer.writerow(['Name', 'Age', 'Grade'])
• writer.writerow(['Ahmed', 20, 'A'])
• “`

Working with JSON

• JSON is used to store structured data (like dictionaries):
• “`python
• import json
• # Save data to JSON
• student = {'name': 'Ali', 'age': 22, 'grade': 'A'}
• with open('student.json', 'w') as file:
• json.dump(student, file)
• # Read JSON
• with open('student.json', 'r') as file:
• data = json.load(file)
• print(data['name'])
• “`

Real Example: Contact Book

• “`python
• import json
• def save_contact(name, phone):
• contacts = []
• try:
• with open('contacts.json', 'r') as file:
• contacts = json.load(file)
• except:
• pass # File doesn't exist yet
• contacts.append({'name': name, 'phone': phone})
• with open('contacts.json', 'w') as file:
• json.dump(contacts, file)
• save_contact('Ahmed', '0300-1234567')
• “`