On Mon, Mar 24, 2008 at 6:19 AM, Julien <[EMAIL PROTECTED]> wrote:
> I would like to do something like:
>
> def called(arg)
> if arg==True:
> !!magic!!caller.return 1
>
> def caller(arg)
> called(arg)
> return 2
>
"called" look like a precondition constrain[1], then It will be nice
to program these features adding this paradigm to python. Next is just
an very reduced example:
<code>
#!/usr/bin/python
class PreconditionViolationError(AssertionError): pass
def requires(predicate, help=None):
'Pre-condition as in http://en.wikipedia.org/wiki/Design_by_contract'
def decorator(wrapped):
def wrapper(*args, **kwds):
if predicate(*args, **kwds):
return wrapped(*args, **kwds)
else:
aux = help or predicate.__doc__ or wrapper.__doc__
raise PreconditionViolationError, "%s, (%s)" %
(wrapper.__name__, help)
# return update_wrapper(wrapper, wrapped) # Requires Python 2.5
return wrapper
return decorator
def validate(called):
'Special pre-condition to return a value'
def decorator(wrapped):
def wrapper(*args, **kwds):
try:
return called(*args, **kwds)
except:
return wrapped(*args, **kwds)
return wrapper
return decorator
def called(arg):
if arg:
return 1
else:
raise PreconditionViolationError, "False arg"
@validate(called)
def caller(arg):
return 2
if __name__ == '__main__':
print 'OK: %s' % caller(True)
print 'NOT OK: %s' % caller(False)
</code>
I included a real-precondition I use in my programs. "validate" is a
metaphor for the sake of this example, to answer the Julien's question
my way.
Regards
[1] http://en.wikipedia.org/wiki/Design_by_contract
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