Chapter 2 · 6 levels

Lists, dictionaries and loops

Hold many values at once, look things up by key, and repeat work with loops and comprehensions, all on Harbor & Pine orders and stock.

Start

One price is a variable. A whole cart of prices is a list. A stock sheet where every product name maps to a count is a dictionary. And going through every order to add something up is a loop.

These three ideas are the foundation of pandas, the library you’ll use from chapter 4 onwards. A pandas column behaves a lot like a list, and a row behaves a lot like a dictionary. Learning them in plain Python first makes pandas feel natural instead of magical.

In this chapter you’ll slice a week of order counts, total a cart, update the stock sheet after a delivery, count orders by sales channel, and filter products with a single readable line. The boss level hands you a small batch of raw orders and asks for revenue by channel, which is exactly the kind of question you’ll answer with pandas later, done by hand.

Levels

  1. Slice a week of orders

    from Megan Collins, Head of Sales

    lists, indexing, slicing, len sum max

    Code

  2. Total a cart with a loop

    from Jennifer Castillo, Support Team Lead

    for loop, accumulator, zip

    Code

  3. Update the stock sheet

    from Debra Marshall, Warehouse Manager

    dictionaries, keys values, get, update

    Code

  4. Count orders by channel

    from Andrew Ramos, Marketing Manager

    dictionaries, counting, get, for loop

    Code

  5. Filter products in one line

    from Thomas Whitaker, Head of Merchandising

    list comprehension, filtering, dictionaries

    Code

  6. Boss: revenue by channel, by hand

    from Megan Collins, Head of Sales

    list comprehension, dictionaries, nested data, accumulator

    Boss · 3 steps