python 用元类检查做约束
下面有一个元类，它用来检测重载方法，确保它的调用参数跟父类中原始方法有着相同的参数签名
from inspect import signature import logging
class MatchSignaturesMeta(type):
def __init__(self, clsname, bases, clsdict):
super().__init__(clsname, bases, clsdict)
sup = super(self, self)
for name, value in clsdict.items():
if name.startswith('_') or not callable(value):
continue
# Get the previous definition (if any) and compare the signatures
prev_dfn = getattr(sup,name,None)
if prev_dfn:
prev_sig = signature(prev_dfn)
val_sig = signature(value)
if prev_sig != val_sig:
logging.warning('Signature mismatch in %s. %s != %s',
value.__qualname__, prev_sig, val_sig)Example
class Root(metaclass=MatchSignaturesMeta): pass
class A(Root): def foo(self, x, y): pass
def spam(self, x, *, z):
passClass with redefined methods, but slightly different signatures
class B(A): def foo(self, a, b): pass
def spam(self,x,z):
pass运行结果
WARNING:root:Signature mismatch in B.spam. (self, x, *, z) != (self, x, z) WARNING:root:Signature mismatch in B.foo. (self, x, y) != (self, a, b)
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