PCEP Computer Programming and Python Fundamentals Practice Question
A Python function is designed to return the first element of a list. However, when passed an empty list, it raises an IndexError. Which best practice should be applied to handle this robustly?
⚠ Common exam trap
Python Institute often tests the distinction between LBYL (look before you leap) and EAFP (easier to ask for forgiveness than permission) patterns, and the trap here is that candidates may incorrectly think catching an IndexError with try-except is the more 'Pythonic' approach, when in fact a simple conditional check is more appropriate for this predictable scenario.
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
✓
Check if len(lst) > 0 before accessing lst[0].
Checking the length of the list before accessing an index is the most explicit and readable way to avoid an IndexError. This approach follows the principle of 'look before you leap' (LBYL), which is a common defensive programming pattern in Python. It clearly communicates the intent to handle empty lists without relying on exception handling for normal control flow.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use try-except to catch IndexError and return None.
Why it's wrong here
Valid but less readable than a simple check.
- ✓
Check if len(lst) > 0 before accessing lst[0].
Why this is correct
Clear and explicit guard condition.
- ✗
Always return None; let the caller handle IndexError.
Why it's wrong here
Not robust; still raises error.
- ✗
Use a default parameter like lst=[0] to avoid empty list.
Why it's wrong here
Default mutable arguments can cause bugs; not a safe pattern.
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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.