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.
A developer creates a package named 'analytics' with the following structure:
analytics/ __init__.py stats.py models/ __init__.py regression.py
The developer wants the statement 'from analytics import *' to import only the functions 'mean' and 'std' from stats.py. What should be added to analytics/__init__.py?
Nothing; by default, all names are exported.
Why wrong: Default behavior does not export anything via star import; __all__ is needed.
from analytics.stats import *
Why wrong: This would export all names from stats, not just mean and std.
__all__ = ['stats.mean', 'stats.std']
Why wrong: The syntax is incorrect; __all__ should contain simple names.
__all__ = ['mean', 'std']
This defines the public API of the package.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
__all__ = ['mean', 'std']
Option D is correct because in Python, the `__all__` variable in a package's `__init__.py` explicitly controls which names are exported when `from package import *` is used. By setting `__all__ = ['mean', 'std']`, the developer ensures that only the functions `mean` and `std` from `stats.py` are imported into the namespace, as Python will look up these names in the package's scope after executing the `__init__.py` file. This overrides the default behavior where all public names (those not starting with an underscore) would be exported.
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.
Nothing; by default, all names are exported.
Why it's wrong here
Default behavior does not export anything via star import; __all__ is needed.
from analytics.stats import *
Why it's wrong here
This would export all names from stats, not just mean and std.
__all__ = ['stats.mean', 'stats.std']
Why it's wrong here
The syntax is incorrect; __all__ should contain simple names.
__all__ = ['mean', 'std']
Why this is correct
This defines the public API of the package.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Python Institute often tests the misconception that `__all__` can contain dotted paths like `'stats.mean'` to control imports from submodules, when in reality `__all__` only accepts simple attribute names that exist in the package's own namespace.
Detailed technical explanation
When `from package import *` is executed, Python checks for an `__all__` list in the package's `__init__.py`. If `__all__` is defined, only the names in that list are imported; if not defined, Python imports all names that do not start with an underscore, but only those that are actually defined in the package's namespace (e.g., via explicit imports in `__init__.py`). A subtle behavior is that `__all__` can also be used in modules to control `from module import *`, and it must contain strings of attribute names, not dotted paths, because the import mechanism uses `getattr` on the package/module object.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Modules and Packages — This question tests Modules and Packages — Read the scenario before looking for a memorised answer..
The correct answer is: __all__ = ['mean', 'std'] — Option D is correct because in Python, the `__all__` variable in a package's `__init__.py` explicitly controls which names are exported when `from package import *` is used. By setting `__all__ = ['mean', 'std']`, the developer ensures that only the functions `mean` and `std` from `stats.py` are imported into the namespace, as Python will look up these names in the package's scope after executing the `__init__.py` file. This overrides the default behavior where all public names (those not starting with an underscore) would be exported.
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
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