python 标准库中的装饰器（特别是@deprecated）

Question

我需要将例程标记为已弃用，但显然没有可弃用的标准库装饰器。我知道它的配方和警告模块，但我的问题是：为什么这个（常见）任务没有标准库装饰器？

附加问题：标准库中是否有标准装饰器？

Answer 1

我猜原因是 Python 代码不能被静态处理（就像 C++ 编译器所做的那样），在实际使用它之前你不会收到关于使用某些东西的警告。我认为向您的脚本用户发送大量消息“警告：此脚本的此开发人员正在使用已弃用的 API”向用户发送垃圾邮件并不是一个好主意。

更新： 但您可以创建将原始功能转换为另一个功能的装饰器。新功能将标记/检查开关，告知该功能已被调用，并且仅在将开关变为开启状态时才会显示消息。和/或在退出时它可能会打印程序中使用的所有已弃用函数的列表。

Answer 2

这里有一些 sn-p，根据 Leandro 引用的内容进行了修改：

import warnings
import functools

def deprecated(func):
    """This is a decorator which can be used to mark functions
    as deprecated. It will result in a warning being emitted
    when the function is used."""
    @functools.wraps(func)
    def new_func(*args, **kwargs):
        warnings.simplefilter('always', DeprecationWarning)  # turn off filter
        warnings.warn("Call to deprecated function {}.".format(func.__name__),
                      category=DeprecationWarning,
                      stacklevel=2)
        warnings.simplefilter('default', DeprecationWarning)  # reset filter
        return func(*args, **kwargs)
    return new_func

# Examples

@deprecated
def some_old_function(x, y):
    return x + y

class SomeClass:
    @deprecated
    def some_old_method(self, x, y):
        return x + y

因为在某些解释器中，第一个暴露的解决方案（没有过滤器处理）可能会导致警告抑制。

Answer 3

这是另一个解决方案：

这个装饰器（实际上是decorator factory）允许你给出一个reason信息。通过提供源文件名和行号来帮助开发人员诊断问题也更有用。

编辑：此代码使用 Zero 的建议：将 warnings.warn_explicit 行替换为 warnings.warn(msg, category=DeprecationWarning, stacklevel=2)， 它打印函数调用站点而不是函数定义站点。它使调试更容易。

EDIT2：此版本允许开发人员指定可选的“原因”消息。

import functools
import inspect
import warnings

string_types = (type(b''), type(u''))


def deprecated(reason):
    """
    This is a decorator which can be used to mark functions
    as deprecated. It will result in a warning being emitted
    when the function is used.
    """

    if isinstance(reason, string_types):

        # The @deprecated is used with a 'reason'.
        #
        # .. code-block:: python
        #
        #    @deprecated("please, use another function")
        #    def old_function(x, y):
        #      pass

        def decorator(func1):

            if inspect.isclass(func1):
                fmt1 = "Call to deprecated class {name} ({reason})."
            else:
                fmt1 = "Call to deprecated function {name} ({reason})."

            @functools.wraps(func1)
            def new_func1(*args, **kwargs):
                warnings.simplefilter('always', DeprecationWarning)
                warnings.warn(
                    fmt1.format(name=func1.__name__, reason=reason),
                    category=DeprecationWarning,
                    stacklevel=2
                )
                warnings.simplefilter('default', DeprecationWarning)
                return func1(*args, **kwargs)

            return new_func1

        return decorator

    elif inspect.isclass(reason) or inspect.isfunction(reason):

        # The @deprecated is used without any 'reason'.
        #
        # .. code-block:: python
        #
        #    @deprecated
        #    def old_function(x, y):
        #      pass

        func2 = reason

        if inspect.isclass(func2):
            fmt2 = "Call to deprecated class {name}."
        else:
            fmt2 = "Call to deprecated function {name}."

        @functools.wraps(func2)
        def new_func2(*args, **kwargs):
            warnings.simplefilter('always', DeprecationWarning)
            warnings.warn(
                fmt2.format(name=func2.__name__),
                category=DeprecationWarning,
                stacklevel=2
            )
            warnings.simplefilter('default', DeprecationWarning)
            return func2(*args, **kwargs)

        return new_func2

    else:
        raise TypeError(repr(type(reason)))

您可以将此装饰器用于函数、方法和类。

这是一个简单的例子：

@deprecated("use another function")
def some_old_function(x, y):
    return x + y


class SomeClass(object):
    @deprecated("use another method")
    def some_old_method(self, x, y):
        return x + y


@deprecated("use another class")
class SomeOldClass(object):
    pass


some_old_function(5, 3)
SomeClass().some_old_method(8, 9)
SomeOldClass()

你会得到：

deprecated_example.py:59: DeprecationWarning: Call to deprecated function or method some_old_function (use another function).
  some_old_function(5, 3)
deprecated_example.py:60: DeprecationWarning: Call to deprecated function or method some_old_method (use another method).
  SomeClass().some_old_method(8, 9)
deprecated_example.py:61: DeprecationWarning: Call to deprecated class SomeOldClass (use another class).
  SomeOldClass()

EDIT3：这个装饰器现在是弃用库的一部分：

• Python package index (PyPi)
• GitHub website
• Read The Docs
• Twitter

新的稳定版本 v1.2.13 ?

Answer 4

更新：我认为更好的是，当我们只为每个代码行第一次显示 DeprecationWarning 并且我们可以发送一些消息时：

import inspect
import traceback
import warnings
import functools

import time


def deprecated(message: str = ''):
    """
    This is a decorator which can be used to mark functions
    as deprecated. It will result in a warning being emitted
    when the function is used first time and filter is set for show DeprecationWarning.
    """
    def decorator_wrapper(func):
        @functools.wraps(func)
        def function_wrapper(*args, **kwargs):
            current_call_source = '|'.join(traceback.format_stack(inspect.currentframe()))
            if current_call_source not in function_wrapper.last_call_source:
                warnings.warn("Function {} is now deprecated! {}".format(func.__name__, message),
                              category=DeprecationWarning, stacklevel=2)
                function_wrapper.last_call_source.add(current_call_source)

            return func(*args, **kwargs)

        function_wrapper.last_call_source = set()

        return function_wrapper
    return decorator_wrapper


@deprecated('You must use my_func2!')
def my_func():
    time.sleep(.1)
    print('aaa')
    time.sleep(.1)


def my_func2():
    print('bbb')


warnings.simplefilter('always', DeprecationWarning)  # turn off filter
print('before cycle')
for i in range(5):
    my_func()
print('after cycle')
my_func()
my_func()
my_func()

结果：

before cycle
C:/Users/adr-0/OneDrive/Projects/Python/test/unit1.py:45: DeprecationWarning: Function my_func is now deprecated! You must use my_func2!
aaa
aaa
aaa
aaa
aaa
after cycle
C:/Users/adr-0/OneDrive/Projects/Python/test/unit1.py:47: DeprecationWarning: Function my_func is now deprecated! You must use my_func2!
aaa
C:/Users/adr-0/OneDrive/Projects/Python/test/unit1.py:48: DeprecationWarning: Function my_func is now deprecated! You must use my_func2!
aaa
C:/Users/adr-0/OneDrive/Projects/Python/test/unit1.py:49: DeprecationWarning: Function my_func is now deprecated! You must use my_func2!
aaa

Process finished with exit code 0

我们只需点击警告路径，然后转到 PyCharm 中的行。

Answer 5

你可以创建一个 utils 文件

import warnings

def deprecated(message):
  def deprecated_decorator(func):
      def deprecated_func(*args, **kwargs):
          warnings.warn("{} is a deprecated function. {}".format(func.__name__, message),
                        category=DeprecationWarning,
                        stacklevel=2)
          warnings.simplefilter('default', DeprecationWarning)
          return func(*args, **kwargs)
      return deprecated_func
  return deprecated_decorator

然后导入deprecation装饰器如下：

from .utils import deprecated

@deprecated("Use method yyy instead")
def some_method()"
 pass

Answer 6

As muon suggested，您可以为此安装deprecation 包。

deprecation 库为您的测试提供了一个 deprecated 装饰器和一个 fail_if_not_removed 装饰器。

安装

pip install deprecation

示例用法

import deprecation

@deprecation.deprecated(deprecated_in="1.0", removed_in="2.0",
                        current_version=__version__,
                        details="Use the bar function instead")
def foo():
    """Do some stuff"""
    return 1

有关完整文档，请参阅 http://deprecation.readthedocs.io/。