design of python: why is assert a statement and not a function?

Question

In Python, assert is a statement, and not a function. Was this a deliberate decision? Are there any advantages to having assert be a statem

Answer 1

I am no expert in Python, but I believe performance is one of the biggest reason.

if we have assert(expression, explanation) as function, if expression is expensive to evaluate, even we are in non-debug mode, Python needs to evaluate both expression to pass it to the assert function.

By expanding the assert, the expression and explanation statement is in fact not evaluated unless they are really needed (when debug evaluates to true). I believe it is critical if we want to make assert not affecting performance when not necessary (i.e. no performance hit in production system).