What linting is

Linting is static analysis that flags issues like:

• unused imports/variables
• suspicious logic
• inconsistent style
• complexity / maintainability issues

Linting runs without executing your code.

Linting vs formatting vs type checking

• Linting: “this looks wrong / risky / inconsistent”
• Formatting: “make code look consistent” (e.g., Black)
• Type checking: “types don’t match” (e.g., Mypy)

Diagram: quality tools overview

  graph TD
A[Source code] --> B["Formatter\n(Black)"]
A --> C["Linter\n(Pylint/Flake8)"]
A --> D["Type checker\n(Mypy)"]
A --> E["Security scan\n(Bandit)"]
A --> F["Complexity\n(Radon)"]

Why linting matters

• catches bugs before runtime
• keeps large codebases consistent
• makes PR reviews faster

Visualize it

Source code typically passes through a formatter, a linter, and a type checker before a commit is allowed through the quality gate.

  flowchart LR
A["Source code"] --> B["Formatter (black)"]
B --> C["Linter (flake8/pylint)"]
C --> D["Type checker (mypy)"]
D --> E["Pass"]
D --> F["Block commit"]

🧪 Try It Yourself

Exercise 1 – Write a unittest TestCase

Exercise 2 – assertRaises

Exercise 3 – setUp and tearDown