PythonLesson 10 of 16

Dictionaries in Python

A dictionary stores key-value pairs, like a menu: a drink and its price. You find a value by its key, not by position.

Key points

{"latte": 250}: the key is left of the colon, the value right
d["latte"] reads a value, d["cocoa"] = 200 adds or changes one
d.get(key, fallback) doesn't crash when the key is missing
for k, v in d.items(): walks through every pair
Keys are unique and keep the order you added them in

Example

menu = {"latte": 250, "tea": 150}print(menu["latte"])menu["cocoa"] = 200print(menu.get("juice", "not on the menu"))for drink, price in menu.items():    print(drink, price)print("tea" in menu, len(menu))

cocoa went to the end of the dictionary. get returned the fallback text instead of an error, because juice isn't on the menu.

Task

How to use the editor⌘ Enter or Ctrl Enter runs the code, ⇧ ⌘ Enter checks the task.Tab and Shift Tab indent the line or the selection; Esc, then Tab leaves the editor.The check compares what the program printed with the task; spaces at line ends do not matter.After two failed checks you may open the solution. Your code is kept in this browser.

Update the stock: 3 apples were sold and 8 plums arrived (key "plums"). The loop below prints what's left.

stock = {"apples": 12, "pears": 5}# TODO: 3 apples were sold, and 8 plums arrivedfor item, count in stock.items():    print(f"{item}: {count}")

stock = {"apples": 12, "pears": 5}
# TODO: 3 apples were sold, and 8 plums arrived
for item, count in stock.items():
    print(f"{item}: {count}")

Output

What your program prints appears here.