On Thu, Feb 18, 2021 at 11:50:17AM +1300, Greg Ewing wrote:
> It's dead simple to define
> your own blank-object class, and you get to give it a name that
> reflects what you're really doing with it. I don't understand
> why there's such a fascination with things like SimpleNamespace.
Right, it takes only two lines of code. So let's do it!
>>> class Thing:
... pass
...
>>> obj = Thing(attr='value')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: Thing() takes no arguments
Hmmm. Okay, *three* lines of code:
>>> class Thing:
... def __init__(self, **kw):
... vars(self).update(kw)
...
>>> obj = Thing(attr='value')
>>> print(obj)
<__main__.Thing object at 0x7f2b07c23b80>
Damn, that's about as useful as a screen door on a submarine. Let's give
it a repr, so when debugging we can see what it actually is.
So *five* lines of code:
>>> class Thing:
... def __init__(self, **kw):
... vars(self).update(kw)
... def __repr__(self):
... return f'Thing({vars(self)})'
...
>>> obj = Thing(attr='value')
>>> print(obj)
Thing({'attr': 'value'})
>>> obj == Thing(attr='value')
False
Bugger. So **ten** lines of code:
>>> class Thing:
... def __init__(self, **kw):
... vars(self).update(kw)
... def __repr__(self):
... return f'Thing({vars(self)})'
... def __eq__(self, other):
... if isinstance(other, Thing):
... return vars(self) == vars(other)
... else:
... return NotImplemented
...
>>> obj = Thing(attr='value')
>>> print(obj)
Thing({'attr': 'value'})
>>> obj == Thing(attr='value')
True
So we've gone from a trivial two-liner that doesn't do what we need, to
ten lines, without docs or tests.
Or we could just use a one-liner:
>>> from types import SimpleNamespace
and get all of that for free. And if it were a builtin, it would be a
zero-liner.
--
Steve
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