Dictionaries: Key-Value Data

What you will learn

Create and access dictionaries.
Add, update, and remove key-value pairs.
Use get() for safer lookups.
Iterate over keys, values, and items.

The code from this chapter

Type these programs yourself. The predictions below are the exercises; the explanations are in the book.

10.1 A Dictionary Maps Keys to Values

TPRM Lab 10.1: Create a Record

Type this into a file, predict the output, then run it.

Python

student = {
    "name": "Alex",
    "age": 20,
    "grade": 87
}

print(student["name"])
print(student["grade"])
print(len(student))

10.2 Missing Keys

Type this into a file, predict the output, then run it.

Python

student = {"name": "Alex", "grade": 87}
print(student.get("name"))
print(student.get("email"))
print(student.get("email", "Not provided"))

10.3 Iterate Through a Dictionary

TPRM Lab 10.3: Three Iteration Patterns

Type this into a file, predict the output, then run it.

Python

prices = {"apple": 1.25, "banana": 0.75, "pear": 1.10}

for item in prices:
    print(item)

for price in prices.values():
    print(price)

for item, price in prices.items():
    print(item, price)

10.4 A Word Counter

Type this into a file, predict the output, then run it.

Python

text = "red blue red green blue red"
counts = {}

for word in text.split():
    counts[word] = counts.get(word, 0) + 1

print(counts)