Asserts vs. Exceptions: When Should You Use Which for Performance and Code Maintenance?

Using Assert: Performance and Maintenance Considerations

Performance vs. Code Maintenance

The use of asserts as standard code instead of debugging only has both performance and code maintenance implications. Asserts perform a runtime check and raise an AssertionError if the specified condition is not met. While this can provide early detection of invalid program states, it does add a small performance overhead compared to using alternative methods.

Assert vs. Exception

The example code snippet demonstrates two ways to handle an invalid condition where 'x' should not be less than zero:

• Assert:

  assert x >= 0, 'x is less than zero'

• Exception:

  if x < 0:
    raise Exception('x is less than zero')

Asserts are intended to test conditions that should never occur during normal program execution. They are useful for raising an AssertionError early on, potentially preventing further program execution and data corruption. Exceptions, on the other hand, are used for handling errors that can occur and should be handled gracefully.

Global Error Checking

The provided example also raises the question of how to set a business rule that will always check if 'x' is less than zero and raise an error. Using asserts globally at the start of a function is not an appropriate solution, as asserts are only checked during development.

Instead, it's recommended to use custom Exception classes to handle such errors consistently throughout the codebase. These custom exceptions can be raised in the appropriate context and ensure that invalid conditions are always checked.

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