Data Structures in Python

Data Structures

• Lists: Ordered collection of items, can be modified, and can contain duplicate values.
  • Create: my_list = [1, 2, 3]
  • Indexing: my_list[0] returns the first element
  • Slicing: my_list[1:3] returns a subset of the list
• Tuples: Ordered, immutable collection of items.
  • Create: my_tuple = (1, 2, 3)
  • Indexing: my_tuple[0] returns the first element
• Dictionaries: Unordered collection of key-value pairs.
  • Create: my_dict = {'name': 'John', 'age': 30}
  • Access: my_dict['name'] returns the value associated with the key
• Sets: Unordered collection of unique items.
  • Create: my_set = {1, 2, 3}
  • Operations: union, intersection, difference

Object-Oriented Programming

• Classes: Blueprints for creating objects.
  • Define: class MyClass: pass
  • Instantiate: my_obj = MyClass()
• Objects: Instances of classes.
  • Attributes: my_obj.my_attribute
  • Methods: my_obj.my_method()
• Inheritance: Mechanism for creating a new class from an existing class.
  • Single inheritance: class Child(Parent): pass
  • Multiple inheritance: class Child(Parent1, Parent2): pass

Exception Handling

• Try-Except Blocks: Catch and handle exceptions.
  • try: ... except ExceptionType: ...
  • try: ... except ExceptionType as e: ...
• Raising Exceptions: Manually raise an exception.
  • raise ExceptionType("Error message")
• Custom Exceptions: Define and raise custom exceptions.
  • class MyException(Exception): pass

File Input/Output

• Reading Files:
  • open() function: file = open('file.txt', 'r')
  • read() method: file.read()
• Writing Files:
  • open() function: file = open('file.txt', 'w')
  • write() method: file.write('Hello, World!')
• CSV and JSON Files:
  • csv module: import csv
  • json module: import json

Web Development

• Flask: Micro web framework.
  • Create app: from flask import Flask; app = Flask(__name__)
  • Define routes: @app.route('/')
• Django: High-level web framework.
  • Create project: django-admin startproject myproject
  • Define models: from django.db import models
• Templates: Separating presentation logic from application logic.
  • Template engines: Jinja2, Mustache
  • Template inheritance: extends keyword

Data Structures

• Lists are ordered collections of items that can be modified and contain duplicate values.
• Lists can be created using square brackets [] and elements can be accessed using indexing.
• Slicing allows retrieving a subset of a list using list[start:stop].

Tuples

• Tuples are ordered, immutable collections of items.
• Tuples can be created using parentheses () and elements can be accessed using indexing.

Dictionaries

• Dictionaries are unordered collections of key-value pairs.
• Dictionaries can be created using curly brackets {} and values can be accessed using keys.
• Keys must be unique and immutable.

Sets

• Sets are unordered collections of unique items.
• Sets can be created using curly brackets {} and can be manipulated using union, intersection, and difference operations.

Object-Oriented Programming

Classes

• Classes are blueprints for creating objects.
• Classes can be defined using the class keyword.
• Classes can have attributes and methods.

Objects

• Objects are instances of classes.
• Objects can have attributes and methods.
• Attributes can be accessed using dot notation.
• Methods can be called using dot notation.

Inheritance

• Inheritance is a mechanism for creating a new class from an existing class.
• Single inheritance allows a class to inherit from one parent class.
• Multiple inheritance allows a class to inherit from multiple parent classes.

Exception Handling

Try-Except Blocks

• Try-except blocks are used to catch and handle exceptions.
• The try block contains code that may raise an exception.
• The except block contains code that handles the exception.

Raising Exceptions

• Exceptions can be manually raised using the raise keyword.
• Exceptions can be raised with a custom error message.

Custom Exceptions

• Custom exceptions can be defined by creating a new class that inherits from the Exception class.
• Custom exceptions can be raised using the raise keyword.

File Input/Output

Reading Files

• Files can be read using the open() function in read mode ('r').
• The read() method can be used to read the contents of a file.

Writing Files

• Files can be written using the open() function in write mode ('w').
• The write() method can be used to write to a file.

CSV and JSON Files

• The csv module can be used to read and write CSV files.
• The json module can be used to read and write JSON files.

Web Development

Flask

• Flask is a micro web framework.
• A Flask app can be created using the Flask class.
• Routes can be defined using the @app.route() decorator.

Django

• Django is a high-level web framework.
• A Django project can be created using the django-admin command.
• Models can be defined using the models module.

Templates

• Templates are used to separate presentation logic from application logic.
• Template engines such as Jinja2 and Mustache can be used to render templates.
• Template inheritance can be used to extend templates using the extends keyword.