GH-128520: pathlib ABCs: improve protocol for 'openable' objects #134101
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Rename `pathlib._os.magic_open()` to `vfsopen()`. The new name is a bit less abstract, and it aligns with the `vfspath()` method added in 5dbd27d. Per discussion on discourse[^1], adjust `vfsopen()` so that the following methods may be called: - `__open_reader__()` - `__open_writer__(mode)` - `__open_updater__(mode)` These three methods return readable, writable, and full duplex file objects respectively. In the 'writer' method, *mode* is either 'a', 'w' or 'x'. In the 'updater' method, *mode* is either 'r' or 'w'. Also stop trying built-in `open()` first. I don't know whether this is a good idea or not, so it's best to leave it out for now. In the pathlib ABCs, replace `ReadablePath.__open_rb__()` with `__open_reader__()`, and replace `WritablePath.__open_wb__()` with `__open_writer__()`. [^1]: https://discuss.python.org/t/open-able-objects/90238
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encukou
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May 17, 2025
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| try: | ||
| return cls.__open_reader__(obj) | ||
| except AttributeError: | ||
| if hasattr(cls, '__open_reader__'): | ||
| raise | ||
| raise TypeError(f"{cls.__name__} can't be opened for reading") |
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try should contain only the operation operation that can fail (.):
Suggested change
| try: | |
| return cls.__open_reader__(obj) | |
| except AttributeError: | |
| if hasattr(cls, '__open_reader__'): | |
| raise | |
| raise TypeError(f"{cls.__name__} can't be opened for reading") | |
| try: | |
| open_reader = cls.__open_reader__ | |
| except AttributeError: | |
| raise TypeError(f"{cls.__name__} can't be opened for reading") | |
| else: | |
| return open_reader(obj) |
| """ | ||
| Open the file pointed to by this path and return a file object, as | ||
| the built-in open() function does. | ||
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| Unlike the built-in open() function, this function accepts 'openable' | ||
| objects, which are objects with any of these magic methods: |
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Suggested change
| objects, which are objects with any of these magic methods: | |
| objects, which are objects with any of these special methods: |
See the glossary.
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Rename
pathlib._os.magic_open()tovfsopen(). The new name is a bit less abstract, and it aligns with thevfspath()method added in 5dbd27d.Per discussion on discourse1, adjust
vfsopen()so that the following methods may be called:__open_reader__()__open_writer__(mode)__open_updater__(mode)These three methods return readable, writable, and full duplex file objects respectively. In the 'writer' method, mode is either 'a', 'w' or 'x'. In the 'updater' method, mode is either 'r' or 'w'.
Also stop trying built-in
open()first. I don't know whether this is a good idea or not, so it's best to leave it out for now.In the pathlib ABCs, replace
ReadablePath.__open_rb__()with__open_reader__(), and replaceWritablePath.__open_wb__()with__open_writer__().Footnotes
https://discuss.python.org/t/open-able-objects/90238 ↩