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Python KeyError: Fixing It with dict.get()

dragon["mana"] crashes if mana was never set. dragon.get("mana", 0) doesn't.

  • Lesson 3 of 5
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The dragon explains

A missing key crashes — .get() doesn't have to

  1. The dragon: One more thing about keys: asking for one that doesn't exist is a real crash.

  2. The dragon: dragon["mana"] raises a KeyError if "mana" was never set — Python won't guess a value for you.

    example.pyPython 3
    dragon = {"name": "Ember"}print(dragon["mana"])

  3. The dragon: .get(key, default) asks SAFELY — if the key is missing, you get your own chosen default instead of a crash.

    example.pyPython 3
    print(dragon.get("mana", 0))
    Output0

  4. The dragon: If the key DOES exist, .get() just returns the real value — the default only kicks in when it's actually missing.

Quick check

Check your understanding

Say your answer out loud before reading the marked one. Every wrong option is a mistake real beginners make.

  1. Question 1 of 2

    dragon = {"name": "Ember"}. What happens with print(dragon["mana"])?

    question.pyPython 3
    dragon = {"name": "Ember"}print(dragon["mana"])
    • A KeyError — "mana" was never set as a keyCorrect
    • It prints None, since the key is empty

    Why: A KeyError. dragon["mana"] with square brackets crashes on a missing key — .get() is the safe alternative when a key might not be there.

  2. Question 2 of 2

    dragon = {"hp": 70}. What does dragon.get("hp", 0) return?

    question.pyPython 3
    dragon = {"hp": 70}print(dragon.get("hp", 0))
    • 70 — the real value, since "hp" existsCorrect
    • 0 — the default, since .get() always uses it

    Why: 70. The default in .get(key, default) is a FALLBACK — it only shows up when the key genuinely isn't there.

In the game

What you'll practice

Three levels in the game: one guided first try with the shape of the answer already there, then two to solve on your own.

  1. 1

    GuidedYour first try

    dragon = {"name": "Ember", "hp": 40}. This code crashes with a KeyError trying to print dragon["mana"] — a key that was never set. Run it once to see the real error, then fix it with dragon.get("mana", 0) so it prints 0 instead of crashing.

  2. +2

    PracticeTwo more, on your own

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