01 / START HERE

Look inside your code.

What is Python Anatomy?

Python Anatomy is an interactive way to learn how Python code works. Choose any part of a program—from a whole function down to one word or symbol—to see what it means, why it is there, and how it connects to the rest of the code.

Start with the full program, then explore functions, loops, values, and individual pieces of Python syntax.

Start with the whole store. Explore a function, loop, or value, then return to see how it fits.

Try an example

Python source

import json
from math import ceil as round_up

# Data for our store: text, numbers, collections, and optional values.
prices = {"Milk": 2.99, "Bread": 1.50, "Eggs": 3.25}
categories = {"Dairy", "Bakery"}
store_location = (2, 4)
discount = None
store_open = True

# This for loop runs directly in the program, without a def.
for product in prices:
    print(product, prices[product])

requests = ["Milk", "", "Bread", "Soap", "CHECKOUT", "Eggs"]
cart = []
position = 0

while store_open and position < len(requests):
    product = requests[position]
    position += 1
    if not product:
        continue
    if product == "CHECKOUT" or product == "QUIT":
        break
    if product not in prices:
        continue
    cart.append(product)

def calculate_total(items, price_list):
    total = 0.0
    # This for loop is inside a function; both kinds remain in the program.
    for product in items:
        if product in price_list:
            total = total + price_list[product]
    return total

def ask_customer(default_name="Guest"):
    name = input("Your name: ")
    if not name:
        return default_name
    return name

class Receipt:
    def __init__(self, items, total):
        self.items = items
        self.total = total

def show(self):
        print("Items:", self.items)
        print("Total:", self.total)

def save(self, filename="receipt.json"):
        if not self.items:
            raise ValueError("Cannot save an empty receipt")
        payload = {"items": self.items, "total": self.total}
        with open(filename, "w", encoding="utf-8") as file:
            json.dump(payload, file)
        with open(filename, "r", encoding="utf-8") as file:
            saved_text = file.read()
        return saved_text

subtotal = calculate_total(cart, prices)
if discount is not None:
    subtotal = subtotal - discount
elif subtotal > 0:
    print("No discount applied")
else:
    print("Your cart is empty")

rounded_total = round_up(subtotal)
receipt = Receipt(cart, subtotal)
receipt.show()
print("Rounded up:", rounded_total)
print("Store location:", store_location)
print("Categories:", categories)

# Analyzing this example does not execute it or create a file.
try:
    saved = receipt.save(filename="receipt.json")
except (OSError, ValueError) as error:
    print("Receipt could not be saved:", error)
else:
    print("Saved receipt:", saved)
finally:
    print("Checkout finished")

Whole programs & focused examples

02 / ANATOMY

Pull the code apart

Click to inspect

Jump to a major structure

Find every kind of code in this program

Explode 0% Hide comments

Select a piece, then choose Explore inside. Double-click a piece to enter it directly.

View size100%

Browse the component tree

03 / Inspector (About this piece)

Assignment

Connections across the program

Connected as
Source position

Exact source

Highlighted text belongs to the selected component. Select quotes, commas, or brackets to inspect the syntax.