The correct answer is that the JSON file contains a trailing comma after the last element, which causes the JSONDecodeError. Python’s json.load() strictly enforces the JSON specification (RFC 7159), which explicitly forbids trailing commas in objects or arrays. When the decoder encounters that extra comma, it cannot parse the structure and raises a JSONDecodeError, a common pitfall when working with hand-written or loosely formatted JSON files. On the Certified Associate Python Programmer PCAP exam, this question tests your understanding of Python’s strict JSON parsing behavior versus more lenient formats like Python dictionaries or JavaScript objects. A typical trap is assuming Python’s json module will tolerate trailing commas, but it will not—unlike Python’s own list or dict syntax. To remember this, think: “JSON is comma-strict, Python is comma-lenient.” A useful memory tip: if you see a JSONDecodeError and your file looks clean, always check for a stray comma after the last key-value pair or array element.
PCAP Modules and Packages Practice Question
This PCAP practice question tests your understanding of modules and packages. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Refer to the exhibit. A Python script uses the following code to load the policy. However, it fails with a JSONDecodeError. What is the most likely cause?
```python
import json
with open('policy.json', 'r') as f:
policy = json.load(f)
```
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The JSON file contains a trailing comma after the last element.
Option A is correct because Python's json.load() strictly follows the JSON specification (RFC 7159), which does not allow trailing commas after the last element in an array or object. When the JSON file contains a trailing comma, the decoder raises a JSONDecodeError. This is a common syntax error in hand-written or poorly generated JSON files.
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.
✓
The JSON file contains a trailing comma after the last element.
Why this is correct
JSON does not allow trailing commas; the comma after the second object is invalid.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The policy variable is used before assignment elsewhere in the script.
Why it's wrong here
The error occurs during json.load(), before any assignment to policy.
✗
The file should be opened in binary mode ('rb') instead of text mode.
Why it's wrong here
While binary mode is recommended for consistency, text mode works for JSON and does not cause a JSONDecodeError by itself.
✗
The JSON decoder cannot handle IP addresses in strings.
Common exam trap: answer the scenario, not the keyword
Python Institute often tests the subtle difference between Python's permissive syntax (which allows trailing commas) and the strict JSON specification, leading candidates to incorrectly assume that Python's json module would accept trailing commas.
Detailed technical explanation
How to think about this question
The JSON specification (RFC 7159) explicitly disallows trailing commas, unlike Python's own list/dict syntax which permits them. The json module's decoder is strict by design to ensure interoperability across languages. In real-world scenarios, this error often occurs when JSON is generated by concatenating objects with commas or when using JavaScript-like syntax that allows trailing commas.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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.
Modules and Packages — This question tests Modules and Packages — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The JSON file contains a trailing comma after the last element. — Option A is correct because Python's json.load() strictly follows the JSON specification (RFC 7159), which does not allow trailing commas after the last element in an array or object. When the JSON file contains a trailing comma, the decoder raises a JSONDecodeError. This is a common syntax error in hand-written or poorly generated JSON files.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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This PCAP 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 PCAP exam.
Question Discussion
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