- A
Python caches imported modules in sys.modules, so importing again does not reload the module from disk.
Why wrong: Yes, but the developer is re-running pip install, which should update the module location. The issue is not about sys.modules.
- B
The package 'lib' is being imported as a namespace package, so changes are not picked up.
Why wrong: There is no indication that 'lib' is a namespace package.
- C
The .pyc files are not being invalidated because the timestamps are not updated.
Why wrong: Python checks timestamps; if the .py file is newer, it recompiles.
- D
The editable install may still point to an old copy of the library if the source directory was moved or if there is a stray .egg-link file.
Editable installs use .egg-link or .pth files that can become stale if the source path changes.
Quick Answer
The answer is a stale `.egg-link` file or a moved source directory. When you use `pip install -e` for an editable install, pip creates a pointer file in site-packages that links directly to your source code, allowing changes to be reflected immediately. However, if the source directory is moved, renamed, or if an old `.egg-link` file remains from a previous install, pip will continue referencing the old location, causing the old version to be imported even after re-running the command. On the PCAP exam, this tests your understanding of Python packaging internals and the subtle behavior of development installs, often appearing as a trap where candidates assume re-running `pip install -e` always refreshes the link. The key is remembering that editable installs are directory pointers, not copies—so moving the source breaks the link. Memory tip: think of `.egg-link` as a sticky note pointing to a desk; if you move the desk, the note still points to the empty spot.
PCAP Modules and Packages Practice Question
This PCAP practice question tests your understanding of modules and packages. 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.
Your company has two separate Python packages: 'app' and 'lib'. They are maintained by different teams. 'app' depends on 'lib', but 'lib' is still under development and its API changes frequently. To avoid breaking 'app', the team decides to use a virtual environment and install a specific version of 'lib'. However, during development, they need to test 'app' with the latest 'lib' changes from the Git repository. The current workflow is: (1) activate virtual env, (2) install 'lib' from local source using `pip install -e /path/to/lib`. This installs 'lib' as a development package. But one developer reports that after pulling latest 'lib' changes, importing 'lib' in 'app' still uses the old version even after re-running pip install -e. What is the most likely reason?
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 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
The editable install may still point to an old copy of the library if the source directory was moved or if there is a stray .egg-link file.
The most likely reason is D. When using `pip install -e` (editable install), pip creates a special `.egg-link` file (or similar pointer) in the site-packages directory that points to the source directory. If the source directory was moved, renamed, or if a stale `.egg-link` file remains from a previous install, pip may still reference the old location, causing the old version to be imported even after re-running the install command. This is a known subtlety of editable installs, especially when the source code is managed under version control and the directory structure changes.
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.
- ✗
Python caches imported modules in sys.modules, so importing again does not reload the module from disk.
Why it's wrong here
Yes, but the developer is re-running pip install, which should update the module location. The issue is not about sys.modules.
- ✗
The package 'lib' is being imported as a namespace package, so changes are not picked up.
Why it's wrong here
There is no indication that 'lib' is a namespace package.
- ✗
The .pyc files are not being invalidated because the timestamps are not updated.
Why it's wrong here
Python checks timestamps; if the .py file is newer, it recompiles.
- ✓
The editable install may still point to an old copy of the library if the source directory was moved or if there is a stray .egg-link file.
Why this is correct
Editable installs use .egg-link or .pth files that can become stale if the source path changes.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Python Institute often tests the subtle difference between a stale import cache (sys.modules) and a stale install pointer (editable install link), leading candidates to incorrectly choose the caching option when the real issue is a broken or outdated path reference in the development install.
Detailed technical explanation
How to think about this question
Under the hood, `pip install -e` creates a `.egg-link` file (or a `.pth` file in some configurations) in the site-packages directory that contains the absolute path to the source directory. When Python imports the package, it reads this link and adds the source directory to `sys.path`. If the source directory is moved or the link file is outdated, Python will follow the old path, which may contain an older version of the code. This is a common pitfall in CI/CD pipelines where the working directory changes between runs, or when developers clone the repository to a new location without reinstalling.
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.
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FAQ
Questions learners often ask
What does this PCAP question test?
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 editable install may still point to an old copy of the library if the source directory was moved or if there is a stray .egg-link file. — The most likely reason is D. When using `pip install -e` (editable install), pip creates a special `.egg-link` file (or similar pointer) in the site-packages directory that points to the source directory. If the source directory was moved, renamed, or if a stale `.egg-link` file remains from a previous install, pip may still reference the old location, causing the old version to be imported even after re-running the install command. This is a known subtlety of editable installs, especially when the source code is managed under version control and the directory structure changes.
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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Last reviewed: Jun 30, 2026
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.
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