Python for JavaScript Developers: A Quick Guide

JavaScript dominates the frontend, but Python rules AI, Data Science, and backend scripting. If you know JS, you already know 80% of Python. Here's the other 20%.

Syntax Comparison

Variables and Types

// JS
let name = "Amit";
const PI = 3.14;
let users = ["a", "b"];
let person = { name: "X", age: 20 };

# Python
name = "Amit"  # No let/const
PI = 3.14 # Convention only
users = ["a", "b"]
person = { "name": "X", "age": 20 } # Dictionary

Functions

function greet(name = "World") {
  return `Hello ${name}`;
}

def greet(name="World"):
    return f"Hello {name}" # f-strings are like template literals

Loops

// JS
for (const user of users) {
  console.log(user);
}

# Python
for user in users:
    print(user)

Cool Python Features JS Doesn't Have (Yet)

List Comprehensions

Create lists in one line.

# Create squares of even numbers
numbers = [1, 2, 3, 4, 5]
squares = [x**2 for x in numbers if x % 2 == 0]
# Result: [4, 16]

Tuples

Immutable lists.

point = (10, 20)
# point[0] = 5  <-- Error!
x, y = point    # Destructuring works

Kwargs (Keyword Arguments)

def create_user(name, age, city="Delhi"):
    pass

create_user(age=25, name="Rahul") # Order doesn't matter!

Tooling Ecosystem

Virtual Environments (Crucial!)

In Node, node_modules is local. In Python, packages are global by default. This causes "Dependency Hell."

Always use a virtual environment:

# Create venv
python -m venv venv

# Activate it (Mac/Linux)
source venv/bin/activate

# Install packages locally
pip install requests

Async/Await

It looks almost identical!

import asyncio

async def fetch_data():
    print("Fetching...")
    await asyncio.sleep(1)
    return "Data"

async def main():
    data = await fetch_data()
    print(data)

asyncio.run(main())

Why Learn Python?

1. AI/ML: Access to PyTorch, TensorFlow, HuggingFace.
2. Scripting: Automate server tasks easier than Node.
3. Backend: FastAPI is incredibly fast and strictly typed (Pydantic).

It's a great second language to have in your arsenal.