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Update optional #28435

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merged 2 commits into from
Mar 24, 2023
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Update optional #28435

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e1e6fb3
add optional[any] to cheat sheet
kristapratico Jan 20, 2023
0e5a708
fix
kristapratico Jan 20, 2023
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18 changes: 18 additions & 0 deletions doc/dev/static_type_checking_cheat_sheet.md
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Expand Up @@ -164,6 +164,24 @@ def foo(
...
```

- Do use `Optional` if a parameter can be typed as `Any` or `None`. `Optional[Any]`, or `Union[Any, None]`, is __not__ equal to `Any`.

```python
from typing import Optional, Any

# Yes
def foo(
bar: Optional[Any] = None,
) -> None:
bar.append(1) # error caught at type checking time: Item "None" of "Optional[Any]" has no attribute "append"

# No
def foo(
bar: Any = None,
) -> None:
bar.append(1) # error caught at runtime: AttributeError: 'NoneType' object has no attribute 'append'
```

### Collections

- Do familiarize yourself with the supported operations of various abstract collections in the [collections.abc](https://docs.python.org/3/library/collections.abc.html#collections-abstract-base-classes) docs.
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