Packages: Directory-Level Organization for Multi-Module Code

What might confuse you right now

"I already know modules. Why do I need packages?"

When you've got a bunch of modules, you need directory-level structure. A package is basically "a collection of modules + a namespace."

One-line definition

A package is a directory containing multiple modules, typically marked and managed by __init__.py.

Real-life analogy

A module is like a book. A package is like a section on a bookshelf.

Minimal runnable example

myapp/
  __init__.py
  math_utils.py
  string_utils.py

from myapp.math_utils import add
print(add(2, 3))

Quick quiz (5 min)

1. Create a utils package.
2. Add two modules inside it and import from them.
3. Use __init__.py to expose a unified entry point.

Quiz answer guidelines & grading criteria

• Answer direction: working code that covers core conditions and edge inputs from the prompt.
• Criterion 1 (Correctness): Main flow produces correct results, key branches execute.
• Criterion 2 (Readability): Clear variable names, no excessive nesting.
• Criterion 3 (Robustness): Basic protection against null values, type errors, or unexpected input.

Transfer task (homework)

Take your existing utility functions and split them into three modules (string/number/file), all under one package.

Acceptance criteria

You can independently:

• Create a package directory structure
• Import functions across modules
• Manage a package's public API

Common errors & debugging steps (beginner edition)

• Can't understand the error: read the last line for the error type (e.g., TypeError, NameError), then trace back to the relevant code line.
• Not sure about a variable's value: temporarily add print(variable, type(variable)) at key points to verify data matches expectations.
• Code changes aren't taking effect: confirm the file is saved, you're running the right file, and your terminal environment (venv) is correct.

Common misconceptions

• Misconception: Any directory is automatically a package.
• Reality: You need a clear import path and well-defined structural responsibilities.