Question 324 of 498
PCEP Practice Question: Functions, Tuples, Dictionaries and Exceptions
A function `def process(data):` modifies the dictionary passed as argument by adding a new key. The developer wants to avoid modifying the original dictionary. What should the function do?
⚠ Common exam trap
Python Institute often tests the misconception that mutable objects are passed by value or that changes inside a function are local, leading candidates to incorrectly choose Option C, which is false for mutable types like dictionaries and lists.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a copy of the dictionary at the start: `data = data.copy()`
Dictionaries are mutable objects in Python, so passing a dictionary to a function passes a reference to the same object. Calling `data.copy()` creates a shallow copy of the dictionary, allowing the function to modify the copy without affecting the original dictionary. This is the standard Pythonic way to avoid side effects on mutable arguments.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Create a copy of the dictionary at the start: `data = data.copy()`
Why this is correct
copy() creates a shallow copy, avoiding modification of original.
- ✗
Add the key, then delete it at the end.
Why it's wrong here
The original is still modified temporarily.
- ✗
Modify directly; changes to mutable objects are local only.
Why it's wrong here
Changes to the dictionary are visible outside the function.
- ✗
Convert the dictionary to a tuple before processing.
Why it's wrong here
Tuples are immutable, but conversion changes the data structure.
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Last reviewed: Jun 30, 2026
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