#!/usr/bin/env python3
"A decorator to use Python3 annotations to type-check inputs and outputs"
import functools
def typecheck(f):
@functools.wraps(f)
def decorated(*args, **kws):
for i, name in enumerate(f.__code__.co_varnames):
argtype = f.__annotations__.get(name)
# Only check if annotation exists and it is as a type
if isinstance(argtype, type):
# First len(args) are positional, after that keywords
if i < len(args):
assert isinstance(args[i], argtype)
elif name in kws:
assert isinstance(kws[name], argtype)
result = f(*args, **kws)
returntype = f.__annotations__.get('return')
if isinstance(returntype, type):
assert isinstance(result, returntype)
return result
return decorated
#################################
# Simple self-test and examples
#################################
def check(func, TESTS):
for test in TESTS:
try:
args = test[:-1]
expectation = test[-1]
print("TEST: %s%r -> float ... " % (func.__name__, args), end="")
result = func(*args)
if expectation == "SUCCEED":
print("Succeed as expected")
else:
print("Succeed incorrectly")
except AssertionError:
if expectation == "FAIL":
print("Failed as expected")
else:
print("Failed incorrectly")
if __name__ == "__main__":
@typecheck
def happy1(a:int, b:list, c:tuple=(1,2,3)) -> float:
return 3.14
@typecheck
def happy_with_nontype(a:int, b:list, x:"non-type", c:tuple=(1,2,3)) -> float:
return 3.14
@typecheck
def happy_wo_annotation(a:int, b, c:tuple=(1,2,3)) -> float:
return 3.14
@typecheck
def unhappy1(a:int, b:str) -> float:
return 314 # This can never succeed in return type
check(happy1, [
(17, ['a','b'], "SUCCEED"),
(17, ['a','b'], (4,5,6), "SUCCEED"),
(17.0, ['a','b'], (4,5,6), "FAIL"),
(17, ('a','b'), "FAIL")])
check(happy_with_nontype, [
(17, ['a','b'], "whatever", "SUCCEED"),
(17, ['a','b'], 0xDEADBEAF, (4,5,6), "SUCCEED"),
(17.0, ['a','b'], "whatever", (4,5,6), "FAIL"),
(17, ('a','b'), "whatever", "FAIL")])
check(happy_wo_annotation, [
(17, 'b', "SUCCEED"),
(17, ['a','b'], (4,5,6), "SUCCEED"),
(17.0, 'b', (4,5,6), "FAIL"),
(17, 'b', [4,5,6], "FAIL")])
check(unhappy1, [
(17, "x", 'FAIL'),
(1.7, "x", 'FAIL')])
Diff to Previous Revision
--- revision 4 2013-05-23 22:45:09
+++ revision 5 2013-05-23 22:46:19
@@ -33,7 +33,7 @@
print("TEST: %s%r -> float ... " % (func.__name__, args), end="")
result = func(*args)
if expectation == "SUCCEED":
- print("Succeeded as expected")
+ print("Succeed as expected")
else:
print("Succeed incorrectly")
except AssertionError:
