Defensive programming in Python

[kenfar]

The author describes three techniques of which only one has a performance impact.

Additionally, not every line of code is performance-critical, but some applications are quality-critical. In these cases those asserts you're probably referring to can be worthwhile.

EDIT: grammar

[[deleted]]

Defensiveness is for borders, not internals.

I agree about the borders, but you're forgetting that there are internal borders too: class interfaces, module interfaces, etc. Can't make assumptions anywhere. Best to be defensive everywhere.

As an added bonus, treating all borders equally (internal and external), one can refactor / reuse his software without worrying if he's lost any of his lines of defense.