我们正在开发一个
python库,并希望改变某些函数中某些函数参数的命名方式.
我们希望保持向后兼容性,因此我们希望找到一种为函数参数创建别名的方法.
这是一个例子：
旧版：
- class MyClass(object):
- def __init__(self,object_id):
- self.id = object_id
新版本：
- class MyClass(object):
- def __init__(self,id_object):
- self.id = id_object
我们如何使类与两种调用方式兼容：
- object1 = MyClass(object_id=1234)
- object2 = MyClass(id_object=1234)
我当然可以创建这样的东西：
- class MyClass(object):
- def __init__(self,object_id=None,id_object=None):
- if id_object is not None:
- self.id = id_object
- else:
- self.id = object_id
但是,它会改变参数的数量,我们严格要避免这种情况.
有没有办法声明方法别名或参数别名？
解决方法
你可以写一个装饰者：
- import functools
- import warnings
- def deprecated_alias(**aliases):
- def deco(f):
- @functools.wraps(f)
- def wrapper(*args,**kwargs):
- rename_kwargs(f.__name__,kwargs,aliases)
- return f(*args,**kwargs)
- return wrapper
- return deco
- def rename_kwargs(func_name,aliases):
- for alias,new in aliases.items():
- if alias in kwargs:
- if new in kwargs:
- raise TypeError('{} received both {} and {}'.format(
- func_name,alias,new))
- warnings.warn('{} is deprecated; use {}'.format(alias,new),DeprecationWarning)
- kwargs[new] = kwargs.pop(alias)
- class MyClass(object):
- @deprecated_alias(object_id='id_object')
- def __init__(self,id_object):
- self.id = id_object
或者,由于您使用的是Python 3,因此可以使object_id成为仅限关键字的参数：
- import warnings
- class MyClass(object):
- # v Look here
- def __init__(self,id_object=None,*,object_id=None):
- if id_object is not None and object_id is not None:
- raise TypeError("MyClass received both object_id and id_object")
- elif id_object is not None:
- self.id = id_object
- elif object_id is not None:
- warnings.warn("object_id is deprecated; use id_object",DeprecationWarning)
- self.id = object_id
- else:
- raise TypeError("MyClass missing id_object argument")