Quick Answer
The answer is to use `counts.setdefault('apple', 0)` before incrementing. This method is correct because `setdefault` inserts the key with a default value of 0 only if it does not already exist, then returns the current value—allowing the subsequent `+= 1` to operate safely without raising a KeyError. On the Certified Entry-Level Python Programmer PCEP exam, this tests your understanding of dictionary methods for handling missing keys, a common scenario in counting or tallying tasks. A frequent trap is attempting direct assignment or using `get()` without reassigning, which fails to update the dictionary. The key concept here is that `setdefault` combines a lookup, conditional insert, and value return in one atomic step, making it more concise than an explicit `if` check. Memory tip: think of "set default" as "set it and forget it"—the method ensures the key exists with a starting value, so you can safely increment without worrying about initialization.
This PCEP practice question tests your understanding of functions, tuples, dictionaries and exceptions. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A script uses a dictionary to store counts of words. The code `counts['apple'] += 1` raises a KeyError the first time because the key doesn't exist. Which approach best solves this?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Use `counts.setdefault('apple', 0)` then increment.
setdefault initializes if missing, then increment.
Use `try-except` to catch KeyError and then set the key.
Why wrong: Works but not the best practice.
Use `counts['apple'] = counts.get('apple') + 1`
Why wrong: get returns None if missing, causing TypeError.
Use `if 'apple' in counts:` before incrementing.
Why wrong: Does not handle the first occurrence.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Use `counts.setdefault('apple', 0)` then increment.
Option A is correct because `setdefault('apple', 0)` inserts the key with a default value of 0 if it does not exist, then returns the value (0). After that, `counts['apple'] += 1` increments safely. This avoids a KeyError without requiring an explicit check or exception handling, making it the most concise and Pythonic approach for initializing missing dictionary keys.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Use `counts.setdefault('apple', 0)` then increment.
Why this is correct
setdefault initializes if missing, then increment.
Clue confirmation
The clue words "best", "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Use `try-except` to catch KeyError and then set the key.
Why it's wrong here
Works but not the best practice.
Use `counts['apple'] = counts.get('apple') + 1`
Why it's wrong here
get returns None if missing, causing TypeError.
Use `if 'apple' in counts:` before incrementing.
Why it's wrong here
Does not handle the first occurrence.
Common exam traps
Python Institute often tests the misconception that `dict.get()` can be used directly in an increment expression, but candidates forget that `get` returns `None` for missing keys, leading to a TypeError rather than a KeyError.
Detailed technical explanation
Under the hood, `dict.setdefault(key, default)` performs a single lookup and, if the key is missing, inserts it with the default value in one operation. This is more efficient than a separate `if key in dict` check followed by assignment, which involves two dictionary lookups. In real-world scenarios like word counting in large text corpora, using `collections.defaultdict(int)` is even more efficient because it eliminates the need for explicit initialization entirely, but `setdefault` is a standard library alternative that works without importing additional modules.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the PCEP exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Functions, Tuples, Dictionaries and Exceptions — This question tests Functions, Tuples, Dictionaries and Exceptions — Read the scenario before looking for a memorised answer..
The correct answer is: Use `counts.setdefault('apple', 0)` then increment. — Option A is correct because `setdefault('apple', 0)` inserts the key with a default value of 0 if it does not exist, then returns the value (0). After that, `counts['apple'] += 1` increments safely. This avoids a KeyError without requiring an explicit check or exception handling, making it the most concise and Pythonic approach for initializing missing dictionary keys.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "best", "first". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Read the scenario before looking for a memorised answer.
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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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