Quick Answer
The correct approach is to use a list comprehension with `isinstance(item, str)`, as this reliably filters a list by type in Python by checking whether each element is an instance of the string class. While `type(item) == str` also works, `isinstance()` is preferred because it handles inheritance correctly—for example, if a custom class inherits from `str`, `isinstance()` will still identify it as a string, whereas `type()` would not. On the Certified Entry-Level Python Programmer PCEP exam, this question tests your understanding of type checking and list comprehensions, a common topic in the data types and collections section. A frequent trap is using `type(item) is str` or forgetting that `isinstance()` accepts a tuple of types for multiple checks. To remember, think: “isinstance is inclusive, type is exclusive”—`isinstance` includes subclasses, while `type` demands an exact match.
This PCEP practice question tests your understanding of control flow, loops, lists and logic. 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 list contains strings and numbers: items = ['apple', 10, 'banana', 20]. A programmer wants to create a new list that contains only the strings. Which approach is correct?
[item for item in items if item.isdigit()]
Why wrong: isdigit() only works on strings and would cause error on numbers.
[item for item in items if type(item) is 'str']
Why wrong: type() returns a type object, not a string.
[item for item in items if type(item) == str]
Correct, though isinstance is preferred.
[item for item in items if isinstance(item, str)]
Correct and best practice.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
[item for item in items if type(item) == str]
Option C is correct because `type(item) == str` directly compares the type of each item to the `str` type object, which returns `True` for strings and `False` for numbers. This is a valid and explicit way to filter the list comprehension to only include string elements.
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.
[item for item in items if item.isdigit()]
Why it's wrong here
isdigit() only works on strings and would cause error on numbers.
[item for item in items if type(item) is 'str']
Why it's wrong here
type() returns a type object, not a string.
[item for item in items if type(item) == str]
Why this is correct
Correct, though isinstance is preferred.
Related concept
Read the scenario before looking for a memorised answer.
[item for item in items if isinstance(item, str)]
Why this is correct
Correct and best practice.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Python Institute often tests the distinction between comparing a type object to a string literal (e.g., `type(item) is 'str'`) versus comparing to the actual type object (e.g., `type(item) == str`), trapping candidates who mistakenly think `'str'` is the same as `str`.
Detailed technical explanation
In Python, `type(item) == str` checks equality between type objects, which works because `type(item)` returns the exact class object. The `isinstance()` function (option D) is actually the more robust and recommended approach because it handles inheritance correctly (e.g., if a class subclasses `str`, `isinstance` returns `True` while `type() == str` returns `False`). In real-world code, using `isinstance` is preferred for polymorphism and maintainability.
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
Control Flow, Loops, Lists and Logic — This question tests Control Flow, Loops, Lists and Logic — Read the scenario before looking for a memorised answer..
The correct answer is: [item for item in items if type(item) == str] — Option C is correct because `type(item) == str` directly compares the type of each item to the `str` type object, which returns `True` for strings and `False` for numbers. This is a valid and explicit way to filter the list comprehension to only include string elements.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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