Python Overview

Python Modules

• A file with reusable Python code (functions, classes, variables).

• Example: custom .py files or sys, math module

Python Package

• A folder with related modules, including an __init__.py file.

• Example: numpy or custom module directories.

• pip is a tool in Python to install & manage Python packages or libraries from the Python Package Index (PyPI).

Python Virtual Environment

• Isolated environment for project-specific dependencies.

• Create: python -m venv <env_name>

• Activate: source <env_name>/bin/activate

Command Line Args

Python in build sys module

import sys # python inbuild sys module, which is used for command line args

num1 = float(sys.argv[1])

Environment Variables

Env vars used for sensitive data, which we can’t hardcoded:

• API keys

• passwords

• tokens

• certificates

Declare Env vars in terminal:

export password=”pass@123”

Code:

import os

pass = os.getenv("password")

File Operation of Windows

• Open: open() with modes (r, w, etc.), e.g., open("file.txt", "r").

• Read: Use read(), readline(), or readlines() to fetch content.

• Write: Use write() or writelines() in modes like w or a.

• Close: Use close() or with for auto-closing.

Module

Requests

The requests module in Python simplifies HTTP requests to interact with web servers.

• Purpose: Send HTTP methods (GET, POST, etc.) and handle responses via API.

• Features: Manage headers, cookies, auth, and work with JSON or text.

• Install: pip install requests

import requests  
response = requests.get("https://example.com")  
print(response.status_code)  # Status code  
print(response.text)         # Response body

Boto3

• AWS SDK for Python to interact programmatically with AWS services.

• Ideal for automating AWS workflows and managing resources efficiently

• Building serverless applications with services like Lambda and DynamoDB.

import boto3

# Initialize S3 client
s3 = boto3.client('s3')

# Upload a file to S3
s3.upload_file('local_file.txt', 'my-bucket', 'remote_file.txt')

Flask

It’s a lightweight web framework in Python used to build web applications with added functionality.

Decorators:

• It’s a special function in Python used to modify the behaviour of another function.

• It written above function with @ symbol.

from flask import Flask

app = Flask(__name__)

@app.route("/greet")  # Flask decorator that connects a URL('/greet') route to a function
def greet():
    return "Greetings from Flask!"

if __name__ == "__main__":
    app.run()

Constructor

It’s special method in a class that runs automatically when you create an object.

__init__()

# __name__ special build-in variable
__name__ = __main__ # Runs code only when file is executed directly