I'm not sure if this has been done before, but I couldn't easily find
any prior work on Google, so here I present a simple decorator for
documenting and verifying the type of function arguments.
Feedback/suggestions/criticism is welcome.
'''
2006.12.21 Created.
'''
import unittest
import inspect
def arguments(*args):
'''A simple decorator for formally documenting
and verifying argument types.
usage:
@arguments(type1, type2, [type3.1, type3.2, ..., type3.N],
type4, ..., typeN)
def somefunc(arg1, arg2, arg3, arg4, ..., argN):
do stuff
return
'''
return lambda f:_Arguments(f, *args)
class _Arguments(object):
# todo: extend to verify Zope interfaces
def __init__(self, fn, *args):
self.fn = fn
# create argument type list
self.arguments = []
for arg in args:
if not isinstance(arg, list):
arg = list([arg])
arg = set(arg)
self.arguments.append(arg)
# create name-to-index lookup
argNames, varArgName, varkwName, defaults =
inspect.getargspec(fn)
assert len(argNames) == len(self.arguments), 'list of argument
types must match the number of arguments'
self.argNameToIndex = {}
for i,name in enumerate(argNames):
self.argNameToIndex[name] = i
if defaults and i >= len(self.arguments)-len(defaults):
# add default type to allowable types
self.arguments[i].add(type(defaults[i-(len(self.arguments)-len(defaults))]))
def verify(self, value, i):
'''Returns true if the value matches the allowable types
for the ith argument.'''
if not isinstance(i, int):
if i not in self.argNameToIndex:
raise Exception, 'unknown argument name: %s' % i
i = self.argNameToIndex[i]
return type(value) in self.arguments[i]
def verifyAll(self, *values, **kvalues):
'''Returns true if all values matche the allowable types
for their corresponding arguments.'''
for i,value in enumerate(values):
if not self.verify(value, i):
return False
for name,value in kvalues.iteritems():
if not self.verify(value, name):
return False
return True
def __call__(self, *args, **kargs):
assert self.verifyAll(*args, **kargs), 'argument types must be
in the form of %s' % self.arguments
return self.fn(*args, **kargs)
class Test(unittest.TestCase):
def test(self):
@arguments(str, [int, float], list)
def foo(abc, xyz, big=None):
return '%s %s' % (abc, xyz)
self.assertEqual(type(foo), _Arguments)
self.assertEqual(len(foo.arguments), 3)
self.assertEqual(foo.arguments[2], set([list, type(None)]))
self.assertEqual(foo.verify('how', 0), True)
self.assertEqual(foo.verify(123, 0), False)
self.assertEqual(foo.verify(123, 1), True)
self.assertEqual(foo.verify(1.23, 1), True)
self.assertEqual(foo.verifyAll('how',123), True)
self.assertEqual(foo.verifyAll(123,'how'), False)
self.assertEqual(foo.verifyAll(abc='how',xyz=123), True)
self.assertEqual(foo.verifyAll('how',xyz=123), True)
self.assertEqual(foo.verifyAll('how',xyz='oeuuo'), False)
self.assertEqual(foo.verifyAll('how',xyz=123,big=None), True)
self.assertEqual(foo.verifyAll('how',xyz=123,big=[1,2,3]),
True)
self.assertEqual(foo.verifyAll('how',123,[1,2,3]), True)
self.assertEqual(foo.verifyAll('how',123,'asoenhuas'), False)
self.assertTrue(foo('how',123))
self.assertTrue(foo(abc='how',xyz=123,big=None))
if __name__ == '__main__':
unittest.main()
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