如何创建Python名称空间(argparse.parse_args值)? [英] How do I create a Python namespace (argparse.parse_args value)?

问题描述

要交互式测试我的python脚本，我想创建一个Namespace对象，类似于argparse.parse_args()返回的对象. 显而易见的方式，

To interactively test my python script, I would like to create a Namespace object, similar to what would be returned by argparse.parse_args(). The obvious way,

>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> parser.parse_args()
Namespace()
>>> parser.parse_args("-a")
usage: [-h]
: error: unrecognized arguments: - a

Process Python exited abnormally with code 2

可能会由于一个愚蠢的错误而导致Python repl退出(如上所述).

may result in Python repl exiting (as above) on a silly error.

那么，用给定的属性集创建Python名称空间的最简单方法是什么?

例如，我可以即时创建dict(dict([("a",1),("b","c")]))，但不能将其用作Namespace:

E.g., I can create a dict on the fly (dict([("a",1),("b","c")])) but I cannot use it as a Namespace:

AttributeError: 'dict' object has no attribute 'a'

推荐答案

您可以创建一个简单的类:

You can create a simple class:

class Namespace:
    def __init__(self, **kwargs):
        self.__dict__.update(kwargs)

，它在属性方面的作用与argparse Namespace类完全相同:

and it'll work the exact same way as the argparse Namespace class when it comes to attributes:

>>> args = Namespace(a=1, b='c')
>>> args.a
1
>>> args.b
'c'

或者，只需导入类；它可以从argparse模块中获得:

Alternatively, just import the class; it is available from the argparse module:

from argparse import Namespace

args = Namespace(a=1, b='c')

从Python 3.3开始，还有 types.SimpleNamespace ，实际上执行相同的操作:

As of Python 3.3, there is also types.SimpleNamespace, which essentially does the same thing:

>>> from types import SimpleNamespace
>>> args = SimpleNamespace(a=1, b='c')
>>> args.a
1
>>> args.b
'c'

这两种类型是不同的； SimpleNamespace主要用于sys.implementation属性和time.get_clock_info()的返回值.

The two types are distinct; SimpleNamespace is primarily used for the sys.implementation attribute and the return value of time.get_clock_info().

其他比较:

• 两个类都支持相等性测试；对于相同类的两个实例，如果instance_a == instance_b具有相同的属性且具有相同的值，则为instance_a == instance_b.
• 两个类都有一个有用的__repr__来显示它们具有的属性.
• Namespace()对象支持容器测试；如果名称空间实例具有名称为attrname的属性，则'attrname' in instance为true. SimpleNamespace不.
• Namespace()对象具有未公开的._get_kwargs()方法，该方法返回该实例的(name, value)属性的排序列表.您可以使用sorted(vars(instance).items())对于任一类都获得相同的结果.
• 虽然SimpleNamespace()是用C实现的，而Namespace()是用Python实现的，但是属性访问并没有更快，因为它们都使用相同的__dict__存储属性.对于SimpleNamespace()实例，相等性测试和生成表示形式要快一些.

• Both classes support equality testing; for two instances of the same class, instance_a == instance_b is true if they have the same attributes with the same values.
• Both classes have a helpful __repr__ to show what attributes they have.
• Namespace() objects support containment testing; 'attrname' in instance is true if the namespace instance has an attribute namend attrname. SimpleNamespace does not.
• Namespace() objects have an undocumented ._get_kwargs() method that returns a sorted list of (name, value) attributes for that instance. You can get the same for either class using sorted(vars(instance).items()).
• While SimpleNamespace() is implemented in C and Namespace() is implemented in Python, attribute access is no faster because both use the same __dict__ storage for the attributes. Equality testing and producing the representation are a little faster for SimpleNamespace() instances.

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