标签归档：setattr

知识问答

如何在当前模块上调用setattr（）？

问题：如何在当前模块上调用setattr（）？

如何将第一个参数“ object”传递给函数setattr(object, name, value)，以在当前模块上设置变量？

例如：

setattr(object, "SOME_CONSTANT", 42);

具有与以下相同的效果：

SOME_CONSTANT = 42

在包含这些行的模块中（带有正确的object）。

我在模块级别动态生成几个值，由于无法__getattr__在模块级别定义，所以这是我的后备。

点击查看英文原文

What do I pass as the first parameter “object” to the function setattr(object, name, value), to set variables on the current module?

For example:

setattr(object, "SOME_CONSTANT", 42);

giving the same effect as:

SOME_CONSTANT = 42

within the module containing these lines (with the correct object).

I’m generate several values at the module level dynamically, and as I can’t define __getattr__ at the module level, this is my fallback.

回答 0

import sys

thismodule = sys.modules[__name__]

setattr(thismodule, name, value)

或者，不使用setattr（打破问题的字母，但满足相同的实际目的；-）：

globals()[name] = value

注意：在模块范围内，后者等效于：

vars()[name] = value

这更加简洁，但是在函数内部不起作用（vars()给出在其范围内调用的变量：在全局范围内调用时模块的变量，然后可以使用R / W，但在函数中可以使用变量在函数中调用时，然后必须将其视为R / O － Python在线文档对此特定区别可能会造成混淆。

点击查看英文原文 
import sys

thismodule = sys.modules[__name__]

setattr(thismodule, name, value)

or, without using setattr (which breaks the letter of the question but satisfies the same practical purposes;-):

globals()[name] = value

Note: at module scope, the latter is equivalent to:

vars()[name] = value

which is a bit more concise, but doesn’t work from within a function (vars() gives the variables of the scope it’s called at: the module’s variables when called at global scope, and then it’s OK to use it R/W, but the function’s variables when called in a function, and then it must be treated as R/O — the Python online docs can be a bit confusing about this specific distinction).

回答 1

如果必须从模块内部设置模块范围的变量，那有什么问题global呢？

# my_module.py

def define_module_scoped_variables():
    global a, b, c
    a, b, c = 'a', ['b'], 3

从而：

>>> import my_module
>>> my_module.define_module_scoped_variables()
>>> a
NameError: name 'a' is not defined
>>> my_module.a
'a'
>>> my_module.b
['b']
点击查看英文原文

If you must set module scoped variables from within the module, what’s wrong with global?

# my_module.py

def define_module_scoped_variables():
    global a, b, c
    a, b, c = 'a', ['b'], 3

thus:

>>> import my_module
>>> my_module.define_module_scoped_variables()
>>> a
NameError: name 'a' is not defined
>>> my_module.a
'a'
>>> my_module.b
['b']

回答 2

在Python 3.7中，您将可以__getattr__在模块级别使用（相关答案）。

根据PEP 562：

def __getattr__(name):
    if name == "SOME_CONSTANT":
        return 42
    raise AttributeError(f"module {__name__} has no attribute {name}")
点击查看英文原文

In Python 3.7, you will be able to use __getattr__ at the module level (related answer).

Per PEP 562:

def __getattr__(name):
    if name == "SOME_CONSTANT":
        return 42
    raise AttributeError(f"module {__name__} has no attribute {name}")

回答 3

  1. 你不会的 你会做globals()["SOME_CONSTANT"] = 42
  2. 你不会的 您会将动态生成的内容存储在模块以外的其他位置。
点击查看英文原文
  1. You wouldn’t. You would do globals()["SOME_CONSTANT"] = 42
  2. You wouldn’t. You would store dynamically-generated content somewhere other than a module.