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在方法中复制函数签名

signature python-decorators python-3.7 function python

alex · 技术社区 · 5 年前

我正在尝试创建一个函数 Bar.bar 签名并复印文件( OP )来自 foo :

from inspect import signature
import functools
from typing import Callable

def deco_meta_copy_signature(signature_source: Callable):
    def deco(target: Callable):
        @functools.wraps(target)
        def tgt(*args, **kwargs):
            signature(signature_source).bind(*args, **kwargs)
            return target(*args, **kwargs)
        tgt.__signature__ = signature(signature_source)
        tgt.__doc__ = signature_source.__doc__
        print('Signature 1)', signature(tgt))
        return tgt
    return deco

def foo(a, b, c=0, d=1, **kwargs):
    """ foo! """
    pass

class Bar:
    @deco_meta_copy_signature(foo)
    def bar(self):
        pass

b = Bar()
print('Signature 2)', signature(b.bar))

其中打印:

Signature 1) (a, b, c=0, d=1, **kwargs)
Signature 2) (b, c=0, d=1, **kwargs)

正如你在书中看到的 签名2 第一个参数不被保留。我假设这与目标函数是方法和接收有关 self 参数我怎样才能补充呢 自己 在拥有所有其他参数的同时?

0 回复 | 直到 5 年前

Booboo 5 年前

下面的方法可以工作,但它是通过更新“private”成员来实现的, _parameters ,当然 Signature 这是我对未来的免责声明。

装饰程序查看目标的签名,以及是否有名为 self ,则如果复制源的签名并在前面加上附加参数:

from inspect import signature, Parameter
import functools
from typing import Callable
from types import MappingProxyType
from collections import OrderedDict
from copy import deepcopy

def deco_meta_copy_signature(signature_source: Callable):
    def deco(target: Callable):
        @functools.wraps(target)
        def tgt(*args, **kwargs):
            signature(signature_source).bind(*args, **kwargs)
            return target(*args, **kwargs)
        sig_s = signature(signature_source)
        sig_t = signature(target)
        parameters = sig_t.parameters
        if len(parameters):
            # get first parameter
            it = iter(parameters)
            param0 = next(it)
            if param0 == 'self':
                #add extra dummy parameter that will be discarded:
                d = OrderedDict()
                d['dummy'] = Parameter('dummy', Parameter.POSITIONAL_OR_KEYWORD)
                d['self'] = Parameter('self', Parameter.POSITIONAL_OR_KEYWORD)
                for k, v in sig_s.parameters.items():
                    d[k] = v
                sig_s = deepcopy(sig_s) # leave actual signature unmodified
                sig_s._parameters = MappingProxyType(d) # accessing "private" member: beware!
        tgt.__signature__ = sig_s
        tgt.__doc__ = signature_source.__doc__
        print('Signature 1)', signature(tgt))
        return tgt
    return deco

def foo(a, b, c=0, d=1, **kwargs):
    """ foo! """
    pass

class Action:
    def doit(self, x=9):
        pass

edit = Action()

class Bar:
    @deco_meta_copy_signature(foo)
    def bar(self):
        pass

    @deco_meta_copy_signature(edit.doit)
    def foo(self):
        pass


@deco_meta_copy_signature(foo)
def bar(x=8):
    pass

@deco_meta_copy_signature(edit.doit)
def foo(x=8):
    pass

b = Bar()
print('Signature 2)', signature(b.bar))
print('Signature 3)', signature(b.foo))
print('Signature 4)', signature(bar))
print('Signature 5)', signature(foo))

印刷品:

Signature 1) (dummy, self, a, b, c=0, d=1, **kwargs)
Signature 1) (dummy, self, x=9)
Signature 1) (a, b, c=0, d=1, **kwargs)
Signature 1) (x=9)
Signature 2) (self, a, b, c=0, d=1, **kwargs)
Signature 3) (self, x=9)
Signature 4) (a, b, c=0, d=1, **kwargs)
Signature 5) (x=9)