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25. Assertions

Assertions are used to check conditions that must hold true during execution.

Basic Usage​

x = 5
assert x > 0, "x must be positive"

If the condition is false, an AssertionError is raised.

When to Use Assertions​

  • Sanity checks during development
  • Not for user input validation (can be disabled with python -O)

Practice Challenge​

Add assertions to a function that calculates the area of a rectangle, ensuring inputs are positive.

Wrap-Up​

Assertions help catch bugs early by verifying assumptions in code.