Collections · Lesson 14 of 25

Dictionaries

Keys and values: a small lookup table.

7 minutes2 games

A dictionary stores key: value pairs in { }. Read a value by its key: student["name"]. .get("x", default) returns a fallback instead of erroring when the key is missing.

Python

student = {"name": "Omar", "level": 3}
student["level"] = 4
student["city"] = "Giza"

print(student["name"], student["level"])
print(student.get("phone", "no phone"))

for key, value in student.items():
    print(key, "->", value)

Tool	Use
`d[key]`	Read; KeyError if missing
`d.get(key, fallback)`	Read with a fallback
`key in d`	Test key membership

Spot the bug

One line raises a KeyError. Which?

Exercise

Print the price of book from the dictionary.

Expected output: 120

Python

prices = {"pen": 5, "book": 120}

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Python

Collections · Lesson 14 of 25

Dictionaries

Keys and values: a small lookup table.

7 minutes2 games

A dictionary stores key: value pairs in { }. Read a value by its key: student["name"]. .get("x", default) returns a fallback instead of erroring when the key is missing.

Python

student = {"name": "Omar", "level": 3}
student["level"] = 4
student["city"] = "Giza"

print(student["name"], student["level"])
print(student.get("phone", "no phone"))

for key, value in student.items():
    print(key, "->", value)

Tool	Use
`d[key]`	Read; KeyError if missing
`d.get(key, fallback)`	Read with a fallback
`key in d`	Test key membership

Spot the bug

One line raises a KeyError. Which?

Exercise

Print the price of book from the dictionary.

Expected output: 120

Python

prices = {"pen": 5, "book": 120}

Learn more from

Played 0 of 2 games