import inspect
def signature(function):
"""Build a string with source code of the function declaration"""
desc = inspect.getargspec(function)
if desc[3]:
ldefault = len(desc[3])
default = desc[3]
sign = ','.join(desc[0][:-ldefault])
else:
ldefault = 0
default=[]
sign = ','.join(desc[0])
for n,v in zip(desc[0][-ldefault:],default):
sign += ','+n+"="+str(v)
if desc[1]:
sign +=',*'+desc[1]
if desc[2]:
sign +=',**'+desc[2]
if sign and sign[0]==',': sign = sign[1:]
return sign
def callsignature(function):
"""Build a string with source code of the function call"""
desc = inspect.getargspec(function)
sign = ','.join(desc[0])
if desc[1]:
sign +=',*'+desc[1]
if desc[2]:
sign +=',**'+desc[2]
if sign and sign[0]==',': sign = sign[1:]
return sign
def contract(function,before,after):
"""Create a function wraper wich test Eiffel-like contract
before is a string that contain preconditions separed by ;
after is a string that contain postconditions
"""
if __debug__:
def mk_condition(code,text):
lc=code.split(';')
code_ins=''
for i in lc:
txt = i.strip()
if txt : code_ins +=' assert '+ txt + ",'" + txt + "'\n"
return code_ins
precondition = mk_condition (before,'precondition')
postcondition = mk_condition (after, 'postcondition')
real_function = function
source = ("def func_contract("+ signature(function) +"):\n" +
precondition +
" result = undercontract_"+function.func_name+"("+
callsignature(function)+")\n"+
postcondition+" return result\n")
exec source
globals()["undercontract_"+function.func_name]=function
return func_contract
else:
return function
# contract test case
def foo(x,y,g=2,z=1,*rt):
return x+y+z*g
foo = contract(foo,'x>1;0<y<100','result>0')
foo(12,31)
class bar:
def __init__(self):
self.x = 0
self.y = 0
def instr(self,n):
self.x = n+1
return n+self.y
instr=contract(instr,'n>1;self.y<10','self.y==0')
x=bar()
x.instr(2)
