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advanced SimpleNamespace typing #688

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itajaja opened this issue Nov 26, 2019 · 5 comments
Open

advanced SimpleNamespace typing #688

itajaja opened this issue Nov 26, 2019 · 5 comments

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@itajaja
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@itajaja itajaja commented Nov 26, 2019

the same way we now have TypedDict, it would be nice to have typed SimpleNamespace with equivalent semantics, so that nested structures can be easily checked. eg

class MySubType(TypedSimpleNamespace):
   bar: int

class MyType(TypedSimpleNamespace):
   foo: MySubType

# correct
a: MyType = SimpleNamespace(foo=SimpleNamespace(bar=1))
# incorrect, `bar` should be a number
a: MyType = SimpleNamespace(foo=SimpleNamespace(bar='abc'))
@JelleZijlstra
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@JelleZijlstra JelleZijlstra commented Nov 26, 2019

I think Protocol can basically be used as your proposed TypedSimpleNameSpace.
@itajaja
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@itajaja itajaja commented Nov 26, 2019 •
edited

as far as I can tell, protocols can be used to cast the simple namespace into, but it won't help me typechecking SimpleNamespce, like in my example snippet. can you provide an example when using protocols where the correct line would succeed and the wrong line would file? I don't believe it's possible without adding a specific SimpleNamespace type
@ilevkivskyi
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@ilevkivskyi ilevkivskyi commented Nov 26, 2019

I think Protocol can basically be used as your proposed TypedSimpleNameSpace.

Almost, but not completely. IIUC auto-generated __init__() signature is important. On the other hand, the latter can be added when support for key types is added.
@itajaja
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@itajaja itajaja commented Nov 26, 2019

the latter can be added when support for key types is added.

thanks @ilevkivskyi can you link to related resources about it?
@ilevkivskyi
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@ilevkivskyi ilevkivskyi commented Nov 26, 2019

We don't have a "centralized" issues to track this, but you can watch python/mypy#7856 and/or python/mypy#7790
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3 participants
@itajaja @JelleZijlstra @ilevkivskyi
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