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Last active Dec 29, 2017
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type checking for python functions. this is way better than PEP 484 type hints and it works for Python 2.x and Python 3.x
from typecheck import typecheck
@typecheck((int, int), dict(c=(int, type(None))), int)
def foo(a, b, c=None):
print("hello", a, b)
return 5 = False
@typecheck((int, int), dict(c=(int, type(None))), str)
def foox(a, b, c=None):
print("hello", a, b)
return 5
# foo has typecheck enabled
foo(1, 2, c=5)
# foox does not have type check enabled
foox('1', '2', '3')
def typecheck(argstypes=[], kwargstypes={},
Assert types of arguments to functions and methods
On any function use the @typecheck decorater
@typecheck((int, int))
def foo(a, b):
The decorator accepts three arguments:
argstypes: tuple of types
kwargstypes: dict of kwarg:tuple of types
returntype: tuple of return types
The default for each is to accept any type.
For methods, use the object type as the first argument to match self:
class Bar:
@typecheck((object, int, int))
def foo(self, a, b):
If you can't use the decorator for some reason, typecheck also works inside functions:
def internal(a, b, c):
typecheck((int, int, int)).ins(a, b, c)
result = 5
return typecheck(returntype=int).out(result)
If you need to use *args and **kwargs:
def internal2(*args, **kwargs):
(a, b, c), kwargs = typecheck((int, int, int)).ins(*args, **kwargs)
typecheck works at run time and thus has some overhead. To deactivate typechecking in
production, set = False in your application's main entry point.
def check_in(*args, **kwargs):
for i, arg in enumerate(args):
msg = "Expected arg {} to be of type {} got {}".format(i, argstypes[i], type(arg))
assert isinstance(arg, argstypes[i]), msg
for kwarg in kwargs.iteritems():
kw, val = kwarg
msg = "Expected kwarg {} to be of type {} got {}".format(kw, kwargstypes[kw], type(val))
assert isinstance(val, kwargstypes[kw]), msg
return args, kwargs
def check_out(result):
msg = "Expected result to be of type {} got {}".format(returntype, type(result))
assert isinstance(result, returntype), msg
return result
def wrap(func):
if not getattr(typecheck, 'active', True):
return func
def check(*args, **kwargs):
check_in(*args, **kwargs)
result = func(*args, **kwargs)
return result
return check
wrap.ins = check_in
wrap.out = check_out
return wrap
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