what is the right way to treat Python argparse.Namespace() as a dictionary?

问题

If I want to use the results of argparse.ArgumentParser(), which is a Namespace object, with a method that expects a dictionary or mapping-like object (see collections.Mapping), what is the right way to do it?

C:\\>python
Python 2.7.3 (default, Apr 10 2012, 23:31:26) [MSC v.1500 32 bit (Intel)] on win
32
Type \"help\", \"copyright\", \"credits\" or \"license\" for more information.
>>> import argparse
>>> args = argparse.Namespace()
>>> args.foo = 1
>>> args.bar = [1,2,3]
>>> args.baz = \'yippee\'
>>> args[\'baz\']
Traceback (most recent call last):
  File \"<stdin>\", line 1, in <module>
TypeError: \'Namespace\' object has no attribute \'__getitem__\'
>>> dir(args)
[\'__class__\', \'__contains__\', \'__delattr__\', \'__dict__\', \'__doc__\', \'__eq__\', \'_
_format__\', \'__getattribute__\', \'__hash__\', \'__init__\', \'__module__\', \'__ne__\',
\'__new__\', \'__reduce__\', \'__reduce_ex__\', \'__repr__\', \'__setattr__\', \'__sizeof__
\', \'__str__\', \'__subclasshook__\', \'__weakref__\', \'_get_args\', \'_get_kwargs\', \'ba
r\', \'baz\', \'foo\']

Is it proper to \"reach into\" an object and use its __dict__ property?

I would think the answer is no: __dict__ smells like a convention for implementation, but not for an interface, the way __getattribute__ or __setattr__ or __contains__ seem to be.

回答1:

You can access the namespace's dictionary with vars():

>>> import argparse
>>> args = argparse.Namespace()
>>> args.foo = 1
>>> args.bar = [1,2,3]
>>> d = vars(args)
>>> d
{'foo': 1, 'bar': [1, 2, 3]}

You can modify the dictionary directly if you wish:

>>> d['baz'] = 'store me'
>>> args.baz
'store me'

Yes, it is okay to access the __dict__ attribute. It is a well-defined, tested, and guaranteed behavior.

回答2:

Straight from the horse's mouth:

If you prefer to have dict-like view of the attributes, you can use the standard Python idiom, vars():

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> args = parser.parse_args(['--foo', 'BAR'])
>>> vars(args)
{'foo': 'BAR'}

— The Python Standard Library, 16.4.4.6. The Namespace object

回答3:

Is it proper to "reach into" an object and use its dict property?

In general, I would say "no". However Namespace has struck me as over-engineered, possibly from when classes couldn't inherit from built-in types.

On the other hand, Namespace does present a task-oriented approach to argparse, and I can't think of a situation that would call for grabbing the __dict__, but the limits of my imagination are not the same as yours.

来源：https://stackoverflow.com/questions/16878315/what-is-the-right-way-to-treat-python-argparse-namespace-as-a-dictionary