Python Modules and Packages 4

Question 1

What is `sys.modules`?

Accepted Answer

A dictionary caching all currently imported modules

Answer

`sys.modules` is a dict mapping module names to module objects; Python checks it first on every import to avoid re-executing module code.

Question 2

What does `pkgutil.iter_modules()` return?

Accepted Answer

An iterator of `(finder, name, ispkg)` tuples for modules in given paths

Answer

`pkgutil.iter_modules(path)` yields named tuples describing each module or subpackage found in the given list of directories.

Question 3

Which attribute of a module object stores the file path where the module was loaded from?

Accepted Answer

__file__

Answer

`module.__file__` is the absolute path to the `.py` (or `.pyc`) file that was executed to create the module.

Question 4

When is `__init__.py` code executed?

Accepted Answer

The first time the package or any of its submodules is imported

Answer

`__init__.py` runs once on the first import of the package; subsequent imports use the cached module from `sys.modules`.

Question 5

What is the difference between a regular package and a namespace package?

Accepted Answer

A regular package has `__init__.py`; a namespace package does not and can span multiple directories

Answer

Regular packages require `__init__.py`; namespace packages (PEP 420) lack it and allow merging directories across multiple locations into one logical package.

Python Practice Test

Python Practice Test

Python Modules and Packages 4