Document TypedDict by JukkaL · Pull Request #3583 · python/mypy

JukkaL · 2017-06-21T16:57:07Z

ilevkivskyi

Very nice explanation. I just have three formatting questions.

ilevkivskyi · 2017-06-21T21:21:57Z

+
+   movie = {'name': 'Blade Runner', 'year': 1982}
+
+Only a fixed of set of string keys is expected (``'name'`` and


An extra "of" here? I would just say "a fixed set of string keys"

ilevkivskyi · 2017-06-21T21:25:26Z

+
+.. note::
+
+  If you pass a TypedDict object as an argument to a function, no type


I am not sure if it is important for RtD, but you use two leading spaces here instead of three as everywhere else.

ilevkivskyi · 2017-06-21T21:28:49Z

+
+.. note::
+
+    You need to install ``mypy_extensions`` using pip to use ``TypedDict``:


And here you have four spaces instead of three.

ilevkivskyi · 2017-06-21T21:37:19Z

(I edited the PR description so that the corresponding issue will be closed automatically).

gvanrossum

Agreed with Ivan, it's a very clear piece of documentation.

gvanrossum · 2017-06-21T21:44:17Z

+
+.. note::
+
+  If you pass a TypedDict object as an argument to a function, no type


If you pass a TypedDict object as an argument to a function
I think you mean here "if you pass a dict literal as an argument to a function expecting a TypedDict object". (Except the term "dict literal" is not used anywhere else in the mypy docs.)

Also it's not just when passing to a function -- it's the same when assigning to a variable that's already typed as a TypedDict. Though that is perhaps too advanced?

gvanrossum · 2017-06-21T21:46:22Z

+
+.. code-block:: python
+
+   movie['name']  # Okay, type is str


Maybe show these examples in a little more context, e.g. name = movie['name']? Then you can refer to the type of the variable in the comment, which is perhaps a simpler concept than the type of an expression.

gvanrossum · 2017-06-21T21:47:02Z

+
+.. code-block:: python
+
+   movie['director']  # Error: 'director' is not a valid key


(Here it's less obvious that adding a variable would help, though for consistency maybe it's still the right thing to do.)

gvanrossum · 2017-06-21T21:54:05Z

+However, mypy still lets use ``[]`` with a partial TypedDict -- you
+just need to be careful with it, as it could result in a ``KeyError``.
+Requiring ``get()`` everywhere would be too cumbersome. (Note that you
+are free to use ``get()`` with total TypedDicts as well.)


Maybe you can explore the subject of totality and subtyping in more depth here? I admit that I'm thoroughly confused about the matter (as you can tell from some of my comments on PR #3558). The explanation later of how you can use subclassing to mix required and non-required items also makes me wonder.

gvanrossum · 2017-06-21T21:54:43Z

+------------------
+
+You can use an alternative, class-based syntax to define a
+TypedDict in Python 3.6:


I'd put "In Python 3.6" in front of the sentence.

JelleZijlstra · 2017-06-22T02:00:05Z

+``'year'`` above), and each key has an independent value type (``str``
+for ``'name'`` and ``int`` for ``'year'`` above). We've previously
+seen the ``Dict[K, V]`` type, which lets you declare uniform
+dictionary types, where every value has the same type, and arbitrary key


"key values" -> "keys" would be more readable.

gvanrossum

LGTM too, but I think we may need to wait until totality is actually merged: #3558.

gvanrossum · 2017-06-23T16:47:48Z

Great, this is now live at http://mypy.readthedocs.io/en/latest/kinds_of_types.html#typeddict

thejohnfreeman · 2018-07-25T18:32:46Z

What happened to this? When I search Google for "mypy typeddict" it takes me to the Kinds of Types page, but this content is no longer there. The only reason I know of it is seeing it in someone else's code. It is still mentioned all over the issue tracker but nowhere in the documentation it seems.

emmatyping · 2018-07-25T18:53:51Z

It moved here http://mypy.readthedocs.io/en/latest/more_types.html#typeddict

Document TypedDict

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ilevkivskyi reviewed Jun 21, 2017

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gvanrossum reviewed Jun 21, 2017

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ilevkivskyi approved these changes Jun 22, 2017

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gvanrossum approved these changes Jun 23, 2017

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JelleZijlstra approved these changes Jun 23, 2017

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ilevkivskyi merged commit 5d85832 into master Jun 23, 2017

ilevkivskyi deleted the typeddict-doc branch June 23, 2017 06:48


		movie = {'name': 'Blade Runner', 'year': 1982}

		Only a fixed of set of string keys is expected (``'name'`` and


		.. note::

		If you pass a TypedDict object as an argument to a function, no type


		.. note::

		You need to install ``mypy_extensions`` using pip to use ``TypedDict``:


		.. code-block:: python

		movie['director'] # Error: 'director' is not a valid key

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JukkaL commented Jun 21, 2017 • edited by ilevkivskyi Loading Uh oh! There was an error while loading. Please reload this page.

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ilevkivskyi commented Jun 21, 2017

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gvanrossum commented Jun 23, 2017

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thejohnfreeman commented Jul 25, 2018

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emmatyping commented Jul 25, 2018

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JukkaL commented Jun 21, 2017 •

edited by ilevkivskyi

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