Mention distinction between Generator and Iterator #4424
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As seen in python/typeshed#1806, `Generator[..., None, None]` is not quite equivalent to `Iterator[...]`, due to the `close()` method on generators. In most cases this probably doesn't matter, since the `close()` method is infrequently used, so I've left the basic structure of the docs the same (recommending `Iterator[...]` first for simple generators). But it's at least worth a mention.
ilevkivskyi
reviewed
Jan 3, 2018
docs/source/kinds_of_types.rst
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| @@ -986,6 +986,9 @@ annotated the first example as the following: | |||
| def squares(n: int) -> Generator[int, None, None]: | |||
| for i in range(n): | |||
| yield i * i | |||
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| This is slightly different from using ``Iterable[int]`` or ``Iterator[int]``, | |||
| since generators have a ``close()`` method that generic iterables don't. | |||
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Generators have also throw and send, maybe you could say explicitly that if one wants to call send, throw or close, then one should use Generator[T, None, None] (this can actually be a generic type alias). Maybe you can illustrate this with a short example, like:
x: Iterator[int]
x.send(None) # Error!
x.close() # Error!
y: Generator[int, None, None]
... # etc.
|
I think it should definitely be mentioned here regardless; if you also want it mentioned in Common Issues I can add that. I added mention of |
ilevkivskyi
approved these changes
Jan 5, 2018
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As seen in python/typeshed#1806,
Generator[..., None, None]is not quite equivalent toIterator[...], due to theclose()method on generators. In most cases this probably doesn't matter, since theclose()method is infrequently used, so I've left the basic structure of the docs the same (recommendingIterator[...]first for simple generators). But it's at least worth a mention.