Steven D'Aprano wrote:
On Fri, 10 Jul 2009 12:27:25 -0400, Charles Yeomans wrote:
(3) assert is absolutely unsuitable for enforcing pre-conditions and
post-
conditions, unless such conditions are mere "guidelines", because
assert
can be switched off at runtime.
Unless, of course, you want to switch off such checking at runtime, as
you might when using a design-by-contract approach.
So is design-by-contract just another way of saying "let's hope the data
is valid, because if it's not, we're screwed"?
Perhaps Python should have a new statement, `assume`, used just like
`assert` except it never actually performs the test or raises an error.
The manual says quite clearly
"The simple form, assert expression, is equivalent to
if __debug__:
if not expression: raise AssertionError"
It should be used when and only when one actually wants the double
condition check, and not as an abbreviation of the second conditional only.
tjr
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