My humble attempt to model pre/postconditions with
decorators :-) It's also my first experiment
with decorators.
If you have any ideas or thoughts on how to
improve the code snippet, I'll be happy to
learn more.
Enjoy :-)
def condition(pretext,posttext=""):
precode=compile(pretext or "True","","eval")
postcode=compile(posttext or "True","","eval")
# function -> decorated(function)
def decorate_condition(function):
# FIXME: Does not work with wrapped functions
argcount=function.func_code.co_argcount
var=function.func_code.co_varnames[0:argcount]
# arguments -> closure(assertion)
def evaluate_condition(*args,**kargs):
# FIXME: check if "var" always contains ordered list of
arguments
# map arguments and
args_seq=[(argname,args[pos]) for pos,argname in
enumerate(var)]
# key-arguments to value
kargs_seq=[(k,v) for k,v in kargs.itervalues()]
environment=args_seq+kargs_seq
# precondition
assert eval(precode,{},dict(environment)),pretext
tmp=function(*args,**kargs)
environment2=environment+[('result',tmp)]
# postcondition
assert eval(postcode,{},dict(environment2)),posttext
return tmp
return evaluate_condition
return decorate_condition
@condition("number>0 and number<2","result>=0")
def sqrt(number):
import math
return math.sqrt(number)
@condition("list(seq) is not None","sum(seq)==result")
def my_sum(seq):
tmp=0
for element in seq:
tmp+=element
return tmp
print sqrt(1.2)
print my_sum([1,2,3])
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