Quiz: Chapter 9 :Python Data Structures (Python for Everybody Specialization) Answers 2025

Question 1

How are Python dictionaries different from Python lists?
✅ Python lists are indexed using integers and dictionaries can use strings as indexes
❌ Dictionaries store a single value
❌ Dictionaries can only store words
❌ Dictionaries aren’t collections

🧠 Explanation:
Lists use numeric indices, while dictionaries use key–value pairs where keys can be strings or numbers.

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Question 2

What is a term commonly used for Python dictionaries in other programming languages?
✅ Associative arrays
❌ Sequences
❌ Lambdas
❌ Closures

🧠 Explanation:
In many languages (like PHP or JavaScript), dictionaries are called associative arrays because they associate keys with values.

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Question 3

What would this code print?

✅ The program would fail with a traceback
❌ -1
❌ 0
❌ candy

🧠 Explanation:
Accessing a missing key directly (like 'candy') causes a KeyError.

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Question 4

What would this code print?

✅ -1
❌ Program fails
❌ ‘candy’
❌ 0

🧠 Explanation:
get() safely looks up a key and returns the default value (-1 here) if the key doesn’t exist.

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Question 5

What is a common use of Python dictionaries?
✅ Building a histogram counting the occurrences of various strings in a file
❌ Computing averages
❌ Splitting strings
❌ Sorting names

🧠 Explanation:
Dictionaries are often used as frequency counters (word counts or histograms).

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Question 6

Which line is equivalent to this logic?

✅ counts[key] = counts.get(key, 0) + 1
❌ counts[key] = counts.get(key, -1) + 1
❌ counts[key] = key + 1
❌ counts[key] = (key in counts) + 1

🧠 Explanation:
get(key, 0) returns 0 if key doesn’t exist — so you can increment safely.

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Question 7

What does this loop iterate through?

✅ It loops through the keys in the dictionary
❌ Through the values
❌ Through integers
❌ Through all dictionaries

🧠 Explanation:
By default, looping over a dictionary iterates over its keys.

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Question 8

Which method gives you all values in a dictionary?
✅ values()
❌ keys()
❌ items()
❌ all()

🧠 Explanation:

• .keys() → list of keys

• .values() → list of values

• .items() → list of (key, value) pairs

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Question 9

Purpose of the second parameter in .get()?
✅ To provide a default value if the key is not found
❌ Alternate key
❌ Value to retrieve
❌ Key to retrieve

🧠 Explanation:
my_dict.get(key, default) prevents a crash by returning default if key doesn’t exist.

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🧾 Summary Table

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