Question 208 of 498
PCEP Practice Question: Functions, Tuples, Dictionaries and Exceptions
Which exception is raised when trying to access a dictionary key that does not exist?
⚠ Common exam trap
Python Institute often tests whether candidates confuse `KeyError` with `ValueError` or `TypeError`, especially when the question involves dictionary operations like `pop()` or `del` on a missing key, where the same `KeyError` is raised.
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
✓
KeyError
In Python, when you attempt to access a dictionary key that does not exist using square bracket notation (e.g., `my_dict['nonexistent']`), the interpreter raises a `KeyError`. This is the standard exception for missing dictionary keys, as defined in the Python language specification. The correct answer is A.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
KeyError
Why this is correct
Accessing a missing key raises KeyError.
- ✗
TypeError
Why it's wrong here
TypeError is for operations on inappropriate types.
- ✗
ValueError
Why it's wrong here
ValueError is for functions with inappropriate value.
- ✗
AttributeError
Why it's wrong here
AttributeError is for invalid attribute references.
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Same concept, more angles
2 more ways this is tested on PCEP
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A dictionary: d = {1: 'a', 2: 'b', 3: 'c'}. Which code will cause a KeyError?
hard- A.d.get(4)
- B.if 4 in d: d[4]
- ✓ C.d[4]
- D.d.setdefault(4, 'd')
Why C: Accessing a dictionary key that does not exist using square bracket notation (d[4]) raises a KeyError. Since the dictionary d has keys 1, 2, and 3, the key 4 is absent, so d[4] triggers the error.
Variation 2. Refer to the exhibit. What is the output?
medium- A.Done
- B.Success\nDone
- ✓ C.Key missing\nDone
- D.Key missing\nSuccess\nDone
Why C: The code attempts to access a dictionary key ('key') that does not exist, which raises a KeyError. The except block catches this specific exception and prints 'Key missing'. After the try-except, the 'finally' block (or code after the try-except) prints 'Done'. The output is therefore 'Key missing' followed by 'Done' on separate lines.
Last reviewed: Jun 30, 2026
This PCEP practice question is part of Courseiva's free Python Institute certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCEP exam.
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