design by contract versus doctest

[Yermat]

Colin Blackburn wrote:
> On Tue, 06 Apr 2004 06:51:16 -0400, Peter Hansen <peter at engcorp.com> wrote:
> 
>> Yermat wrote:
>>
>>> Peter Hansen wrote:
>>>
>>>> But I'm certainly no expert in (or proponent of) DBC...
>>>
>>>  see http://www.python.org/doc/essays/metaclasses/Eiffel.py
>>> to now how to do (at least one way to) design by contract in Python.
>>
>>
>> This doesn't appear to do what the OP says it should do.
>> I see preconditions which, while coded in separate methods
>> from the code for which it is written, still executes
>> every time the method is called.  That is, in terms of the
>> sequence of code, it's the same as just putting the check
>> in at the top of the called method.
> 
> 
> In this case yes because python does not support DbC within itself.  
> However, in a language that does support DbC (Eiffel) these checks can 
> be  turned on during the implementation phase and turned off in the 
> delivered  code. There are techniques in python, java and other 
> languages to  implement DbC using comments and documentation, ie the 
> contract checks are  only executed when a tool/module able to process 
> the structure comments is  loaded.
> 
> DbC though is about design rather than just a way testing of 
> parameters.  It is a philosophy of program design. See Object Oriented 
> Software  Construction, ed 2, by Bertrand Mayer.
> 
> Colin
> -- 

Hi,
Not really each time !
As it uses "assert", it is turn off by using -O option of python or by 
removing the metaclass ! So it work exactly as DBC implemented in 
Eiffel. His author is Bertrand Meyer (with an 'e').
So please re-read it again !

Yermat