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Focusing on FromPy rather than IntoPy 

(as you get IntoPy for free)

Also try and point out that intoPy doesn't mean it's going to convert
something into a python object.
This commit is contained in:
Giles Cope 2020-02-14 06:35:41 +00:00
parent 3c02de2688
commit 6b4a4e881a
1 changed files with 4 additions and 2 deletions
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6
guide/src/conversions.md
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@ -100,9 +100,11 @@ fn main() {
}
```
## `IntoPy<T>`
## `FromPy<T>` and `IntoPy<T>`
Many conversions in PyO3 can't use `std::convert::Into` because they need a GIL token. That's why the `IntoPy<T>` trait offers an `into_py` method that works just like `into`, except for taking a `Python<'_>` argument.
Many conversions in PyO3 can't use `std::convert::From` because they need a GIL token. The `FromPy<T>` trait offers an `from_py` method that works just like `from`, except for taking a `Python<'_>` argument. I.e. FromPy<T> could be converting a rust object into a python object even though it says `FromPy` - it doesn't say anything about which side of the conversion is a python object.
(Just like From<T>, if you implement FromPy<T> you gain a blanket implementation of IntoPy<T> for free.)
Eventually, traits such as `ToPyObject` will be replaced by this trait and a `FromPy` trait will be added that will implement `IntoPy`, just like with `From` and `Into`.