Assertion

Assertions are programming constructs used to check assumptions about the state of a program. An assertion tests whether a specific condition is true—if it isn't, an error is typically raised and the program stops.

x = 10
assert x > 0   # passes
assert x < 5   # raises AssertionError, since x is not less than 5

Purpose of Assertions:

• They help with debugging: you can verify that certain conditions in code hold true during development.

• They document implicit assumptions, e.g., “At this point, the list must have at least one item.”

• They are mainly used during development—assertions are often disabled in production code.

Key Difference from Regular Error Handling:

Assertions are meant to catch programmer errors, not user input or external failures. For example:

• assert age > 0 → inappropriate if age comes from user input.

• Instead, use: if age <= 0: raise ValueError("Age must be positive.")