我希望能够询问类的 __init__
方法它的参数是什么。直接的方法如下:
cls.__init__.__func__.__code__.co_varnames[:code.co_argcount]
但是,如果类有任何装饰器,那将不起作用。它将给出装饰器返回的函数的参数列表。我想深入了解原始的 __init__
方法并获取那些原始参数。在装饰器的情况下,装饰器函数将在装饰器返回的函数的闭包中找到:
cls.__init__.__func__.__closure__[0]
但是,如果闭包中还有其他东西,装饰器可能会不时做一些事情,那就更复杂了:
def Something(test):
def decorator(func):
def newfunc(self):
stuff = test
return func(self)
return newfunc
return decorator
def test():
class Test(object):
@Something(4)
def something(self):
print Test
return Test
test().something.__func__.__closure__
(<cell at 0xb7ce7584: int object at 0x81b208c>, <cell at 0xb7ce7614: function object at 0xb7ce6994>)
然后我必须决定是要装饰器的参数还是原始函数的参数。装饰器返回的函数可以有 *args
和 **kwargs
作为参数。如果有多个装饰器,我必须决定我关心哪一个怎么办?
那么即使函数可能被修饰,查找函数参数的最佳方法是什么?此外,沿着装饰器链返回装饰函数的最佳方法是什么?
更新:
以下是我现在的做法(姓名已更改以保护被告的身份):
import abc
import collections
IGNORED_PARAMS = ("self",)
DEFAULT_PARAM_MAPPING = {}
DEFAULT_DEFAULT_PARAMS = {}
class DICT_MAPPING_Placeholder(object):
def __get__(self, obj, type):
DICT_MAPPING = {}
for key in type.PARAMS:
DICT_MAPPING[key] = None
for cls in type.mro():
if "__init__" in cls.__dict__:
cls.DICT_MAPPING = DICT_MAPPING
break
return DICT_MAPPING
class PARAM_MAPPING_Placeholder(object):
def __get__(self, obj, type):
for cls in type.mro():
if "__init__" in cls.__dict__:
cls.PARAM_MAPPING = DEFAULT_PARAM_MAPPING
break
return DEFAULT_PARAM_MAPPING
class DEFAULT_PARAMS_Placeholder(object):
def __get__(self, obj, type):
for cls in type.mro():
if "__init__" in cls.__dict__:
cls.DEFAULT_PARAMS = DEFAULT_DEFAULT_PARAMS
break
return DEFAULT_DEFAULT_PARAMS
class PARAMS_Placeholder(object):
def __get__(self, obj, type):
func = type.__init__.__func__
# unwrap decorators here
code = func.__code__
keys = list(code.co_varnames[:code.co_argcount])
for name in IGNORED_PARAMS:
try: keys.remove(name)
except ValueError: pass
for cls in type.mro():
if "__init__" in cls.__dict__:
cls.PARAMS = tuple(keys)
break
return tuple(keys)
class BaseMeta(abc.ABCMeta):
def __init__(self, name, bases, dict):
super(BaseMeta, self).__init__(name, bases, dict)
if "__init__" not in dict:
return
if "PARAMS" not in dict:
self.PARAMS = PARAMS_Placeholder()
if "DEFAULT_PARAMS" not in dict:
self.DEFAULT_PARAMS = DEFAULT_PARAMS_Placeholder()
if "PARAM_MAPPING" not in dict:
self.PARAM_MAPPING = PARAM_MAPPING_Placeholder()
if "DICT_MAPPING" not in dict:
self.DICT_MAPPING = DICT_MAPPING_Placeholder()
class Base(collections.Mapping):
__metaclass__ = BaseMeta
"""
Dict-like class that uses its __init__ params for default keys.
Override PARAMS, DEFAULT_PARAMS, PARAM_MAPPING, and DICT_MAPPING
in the subclass definition to give non-default behavior.
"""
def __init__(self):
pass
def __nonzero__(self):
"""Handle bool casting instead of __len__."""
return True
def __getitem__(self, key):
action = self.DICT_MAPPING[key]
if action is None:
return getattr(self, key)
try:
return action(self)
except AttributeError:
return getattr(self, action)
def __iter__(self):
return iter(self.DICT_MAPPING)
def __len__(self):
return len(self.DICT_MAPPING)
print Base.PARAMS
# ()
print dict(Base())
# {}
此时 Base 报告了四个常量的无趣值,实例的字典版本为空。但是,如果您创建子类,您可以重写这四个中的任何一个,或者您可以将其他参数包含在 __init__
中:
class Sub1(Base):
def __init__(self, one, two):
super(Sub1, self).__init__()
self.one = one
self.two = two
Sub1.PARAMS
# ("one", "two")
dict(Sub1(1,2))
# {"one": 1, "two": 2}
class Sub2(Base):
PARAMS = ("first", "second")
def __init__(self, one, two):
super(Sub2, self).__init__()
self.first = one
self.second = two
Sub2.PARAMS
# ("first", "second")
dict(Sub2(1,2))
# {"first": 1, "second": 2}
最佳答案
考虑这个装饰器:
def rickroll(old_function):
return lambda junk, junk1, junk2: "Never Going To Give You Up"
class Foo(object):
@rickroll
def bar(self, p1, p2):
return p1 * p2
print Foo().bar(1, 2)
在其中,rickroll 装饰器采用了 bar 方法,将其丢弃,并用忽略其不同名称(可能还有编号!)参数的新函数替换它,而是返回经典歌曲中的一行。
没有对原始函数的进一步引用,垃圾收集器可以随时将其删除。
在这种情况下,我看不出您如何找到参数名称 p1 和 p2。据我了解,即使是 Python 解释器本身也不知道它们过去被称为什么。
关于python - 在 Python 中查找函数的参数,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/3375573/