The correct answer is to use `return s.translate(str.maketrans('', '', 'aeiou'))` because `str.translate()` builds an internal translation table that removes all specified characters in a single O(n) pass, avoiding the overhead of multiple replacements or intermediate string copies. This method is the most efficient way to remove vowels from a string in Python, as it leverages CPython’s low-level C implementation to process the entire string without looping in Python or generating temporary objects. On the Certified Associate Python Programmer PCAP exam, this question tests your understanding of string transformation methods and performance awareness—a common trap is choosing a loop with `replace()` or a list comprehension, which are slower due to repeated allocations. Remember the mnemonic: “Translate to eliminate—one table, no debate.”
PCAP Strings Practice Question
This PCAP practice question tests your understanding of strings. 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 function receives a string and needs to return a new string with all vowels removed. Which code snippet accomplishes this efficiently?
Option C is correct because `str.translate` with `str.maketrans('', '', 'aeiou')` removes all occurrences of the characters 'a', 'e', 'i', 'o', 'u' in a single pass using an internal translation table, which is highly efficient (O(n) time and minimal overhead). It avoids creating intermediate strings or performing repeated replacements, making it the fastest approach for this task in CPython.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
for v in 'aeiou': s = s.replace(v, '')
Why it's wrong here
Multiple replace calls are inefficient; each creates a new string.
✗
return ''.join([c for c in s if c.lower() not in 'aeiou'])
Why it's wrong here
Works, but list comprehension is Python-level and slightly slower.
translate with a deletion table removes all vowels efficiently.
Related concept
Read the scenario before looking for a memorised answer.
✗
return re.sub('[aeiou]', '', s, flags=re.I)
Why it's wrong here
Works, but regex import and compilation add overhead for a simple task.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Python Institute often tests the distinction between `str.replace` (which creates a new string per call) and `str.translate` (which performs bulk removal in one pass), leading candidates to choose the more familiar but less efficient `replace` loop or the regex approach, which is overkill for simple character removal.
Detailed technical explanation
How to think about this question
Under the hood, `str.maketrans('', '', 'aeiou')` creates a translation table mapping each vowel to `None`, and `str.translate` uses a C-level loop to build the result string in one pass, avoiding Python-level per-character operations. This method is particularly efficient for large strings because it leverages the underlying C implementation of `PyUnicode_Translate`, which directly copies non-removed characters into a new Unicode buffer. In real-world scenarios like sanitizing user input in high-throughput web applications, using `translate` can reduce latency by 10x compared to regex or repeated `replace` calls.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Strings — This question tests Strings — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: return s.translate(str.maketrans('', '', 'aeiou')) — Option C is correct because `str.translate` with `str.maketrans('', '', 'aeiou')` removes all occurrences of the characters 'a', 'e', 'i', 'o', 'u' in a single pass using an internal translation table, which is highly efficient (O(n) time and minimal overhead). It avoids creating intermediate strings or performing repeated replacements, making it the fastest approach for this task in CPython.
What should I do if I get this PCAP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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