Python Beginner Handbook

Leeting Yan

November 27, 2025

Python is simple to learn, expressive to write, and powerful enough to build systems of any scale — from automation scripts to backend APIs and machine learning pipelines.

This handbook contains 20 concise, developer-friendly chapters, each focusing on practical understanding and working examples.

Chapter 1 — What Is Python & Why It Matters

Python is a high-level, cross-platform, readable language created in 1991.
Its design goals:

readability
developer productivity
“batteries-included” standard library
large ecosystem of packages

Python powers:

AI/ML (PyTorch, TensorFlow)
Web APIs (FastAPI, Django)
Automation & scripting
DevOps tools
Data pipelines
Education

Python is often the best first language because concepts transfer well to other languages.

Chapter 2 — Installing Python & Setting Up Your Environment

Install Python

macOS

brew install python

Ubuntu

sudo apt install python3 python3-pip

Windows
Download from https://python.org

Create a project folder

mkdir myproject
cd myproject

Virtual environments

python3 -m venv env
source env/bin/activate  # Windows: env\Scripts\activate

Install packages

pip install requests

Chapter 3 — Running Python: Scripts & REPL

Run a file

python3 hello.py

Use the Python REPL

python3
>>> print("hello")

Great for experimenting.

Use `ipython` (recommended)

pip install ipython
ipython

Chapter 4 — Variables, Expressions & Types

Python uses dynamic typing:

name = "Birdor"
age = 12
price = 19.99
active = True

Common types

str
int
float
bool
list
dict
set
tuple

String formatting

print(f"Welcome, {name}!")

Chapter 5 — Control Flow (if, for, while)

If statements

if age >= 18:
    print("Adult")
else:
    print("Minor")

For loops

for item in ["a", "b", "c"]:
    print(item)

While loops

n = 5
while n > 0:
    print(n)
    n -= 1

Chapter 6 — Functions

Basic function

def greet(name):
    return f"Hello, {name}"

Default arguments

def connect(host="localhost"):
    print(host)

Multiple return values

def stats(a, b):
    return a + b, a * b

s, m = stats(3, 4)

Chapter 7 — Modules & Importing

Import built-in modules

import math
print(math.sqrt(9))

Custom module

utils.py

def add(a, b):
    return a + b

main.py

import utils
print(utils.add(3, 5))

Chapter 8 — Lists & List Comprehensions

Lists

users = ["A", "B", "C"]

Append / remove

users.append("D")
users.remove("B")

List comprehension (Pythonic)

squares = [x*x for x in range(10)]

Chapter 9 — Dictionaries

Basic dictionary

profile = {"name": "Ada", "age": 25}

Access

print(profile["name"])

Iterate

for key, value in profile.items():
    print(key, value)

Dictionaries are essential for manipulating JSON-like data.

Chapter 10 — Strings & Text Processing

Common operations

text = "birdor python"

print(text.upper())
print(text.split())
print("python" in text)

f-strings

name = "Birdor"
print(f"Welcome, {name}")

Joining lists

"-".join(["a", "b", "c"])

Chapter 11 — File Handling

with open("data.txt") as f:
    content = f.read()

Write:

with open("log.txt", "w") as f:
    f.write("hello\n")

JSON:

import json
data = json.load(open("data.json"))

Chapter 12 — Exceptions & Error Handling

Try / except

try:
    x = 1 / 0
except ZeroDivisionError:
    print("Cannot divide by zero")

Finally

try:
    f = open("data.txt")
finally:
    f.close()

Chapter 13 — Classes & Object-Oriented Python

class User:
    def __init__(self, name):
        self.name = name

    def hello(self):
        return f"Hello, {self.name}"

u = User("Birdor")
print(u.hello())

Use classes when organizing behaviors + data.

Chapter 14 — Modules, Packages & Project Structure

Typical structure:

myapp/
  app/
    __init__.py
    models.py
    views.py
    utils.py
  tests/
  main.py

__init__.py makes a folder a Python package.

Chapter 15 — Virtualenv / Pip / Poetry

pip + venv

pip install requests
pip freeze > requirements.txt

Poetry (recommended)

pip install poetry
poetry init
poetry add requests

Creates isolated envs automatically.

Chapter 16 — Testing with pytest

Install:

pip install pytest

test_add.py

def add(a, b):
    return a + b

def test_add():
    assert add(1, 2) == 3

Run:

pytest

Chapter 17 — Pythonic Code & Best Practices

Use list comprehension

[x*x for x in items]

Use context managers

with open("x.txt") as f:
    pass

Use meaningful names

Avoid:

a, b, c

Use:

user_id, price, items

Follow PEP 8

Auto-format with:

pip install black
black .

Chapter 18 — AsyncIO & Concurrency (Beginner Safe)

Async example

import asyncio

async def task():
    print("Running...")
    await asyncio.sleep(1)

asyncio.run(task())

Great for:

network I/O
API servers (FastAPI)
bots and crawlers

Not ideal for CPU-heavy tasks.

Chapter 19 — A Mini Project: CLI Tool

weather.py

import requests
import sys

def weather(city):
    res = requests.get(f"https://wttr.in/{city}?format=3")
    print(res.text)

if __name__ == "__main__":
    weather(sys.argv[1])