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__init__.py
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__init__.py
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from types import FunctionType as function, MethodType as method
###---core---###
class override(object):
"""Use this decorator to assert this callable, classmethod, staticmethod,
or property overrides an attribute of the same type as the decorated attrbute
of its first superclass that has it.
This decorator must be used inside a class which its metaclass is OverridesMeta
or a subclass of it for the decorated attribute to be checked.
Upon success, the class that this decorater was calledinside will set the
decorated attribute's name to the decorated attribute. If the assertion
failed, the class will raise a subclass of OverrideError.
Note: classmethods are treated like methods, staticmethods like functions
For example usage, see testing at the end of this decorator's module.
"""
__slots__ = "__func__",
def __new__(cls, func):
self = object.__new__(cls)
if not callable(func) and not isinstance(func, (classmethod, staticmethod, property)):
raise ValueError("value of func parameter must be callable")
self.__func__ = func
return self
def __eq__(self, other):
return NotImplemented if not isinstance(other, override) else self.__func__ is other.__func__
def __hash__(self):
return hash((self.__func__,))
class OverrideError(AssertionError):
"Callable, classmethod, staticmethod or property does not override"
__slots__ = ()
class OverridesMeta(type):
"Metaclass to support usage of the override decorator"
def __new__(mcls, name, bases, classdict):
cls = type.__new__(mcls, name, bases, classdict)
for key, value in cls.__dict__.items():
if isinstance(value, override):
setattr(cls, key, value)
return cls
def __setattr__(cls, name, value):
if isinstance(value, override):
for b in cls.__bases__:
if hasattr(b, name):
overriden = getattr(b, name)
break
else:
raise OverrideError("no base of %s has attr %s" % (cls.__name__, repr(name)))
kind = function if isinstance(value.__func__, staticmethod) else (
method if isinstance(value.__func__, classmethod) else type(value.__func__)
)
if type(overriden) is not kind:
raise OverrideError("attempt to override a %s object with a %s object" % (
type(overriden).__name__, type(value.__func__).__name__
))
value = value.__func__
return super().__setattr__(name, value)
class OverridesBase(metaclass=OverridesMeta):
"Mixin to allow usage of the override decorator"
__slots__ = ()
###---support for custom metaclasses---###
def create_custom_overrides_meta(mcls, *, name=None, doc=None):
metaclass = mcls
class Meta(metaclass):
def __new__(mcls, name, bases, classdict):
cls = metaclass.__new__(mcls, name, bases, classdict)
for key, value in cls.__dict__.items():
if isinstance(value, override):
setattr(cls, key, value)
return cls
def __setattr__(cls, name, value):
if isinstance(value, override):
for b in cls.__bases__:
if hasattr(b, name):
overriden = getattr(b, name)
break
else:
raise OverrideError("no base of %s has attr %s" % (cls.__name__, repr(name)))
kind = function if isinstance(value.__func__, staticmethod) else (
method if isinstance(value.__func__, classmethod) else type(value.__func__)
)
if type(overriden) is not kind:
raise OverrideError("attempt to override a %s object with a %s object" % (
type(overriden).__name__, type(value.__func__).__name__
))
value = value.__func__
return metaclass.__setattr__(name, value)
Meta.__name__ = name if name != None else "Overrides" + metaclass.__name__
Meta.__doc__ = doc
return Meta
__all__ = ['create_custom_overrides_meta', 'override', 'OverridesMeta', 'OverridesBase', 'OverrideError']
__author__ = "Michael Roberts: chermon3@gmail.com"
__credits__ = "Python 3.7 library"
__date__ = "September 24 2019"
__doc__ = "Module to emulate Java's Override annotation in Python 3.7"
__version__ = 1.0
def main():
class A(OverridesBase):
def __init__(self, **kwds):
"You're average constructor"
self.__dict__.update(kwds)
def b(mcls, self):
"You're average method"
pass
def c(self):
"You're average function"
pass
@classmethod
def d(self):
"You're average classmethod"
pass
@property
def e(self):
"You're average property"
return None
A.b = method(A.b, type)
try:
class B(A):
@override
def b(self):
print("b")
except Exception as e:
print(type(e).__name__, "raised while overriding method 'b' via class B:", e)
try:
class C(A):
@override
def __init__(self, h=None, **kwds):
super().__init__(**{'h':a, **kwds})
@override
def c(self):
print("c")
except Exception as e:
print(type(e).__name__, "raised while overriding function 'c':", e)
try:
class D(A):
@override
@classmethod
def d(self):
print("d")
except Exception as e:
print(type(e).__name__, "raised while overriding classmethod 'd':", e)
try:
class E(A):
@override
@property
def e(self):
return "e"
except Exception as e:
print(type(e).__name__, "raised while overriding property 'e':", e)
try:
class F(A):
@override
@classmethod
def b(mcls, self):
return "f"
except Exception as e:
print(type(e).__name__, "raised while overriding method 'b' via class F:", e)
if __name__ == "__main__":
main()