[issue35950] io.BufferedReader.writabe is False, but io.BufferedReader.truncate does not raise OSError
Change by Steve Palmer : -- nosy: +martin.panter ___ Python tracker <https://bugs.python.org/issue35950> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue35950] io.BufferedReader.writabe is False, but io.BufferedReader.truncate does not raise OSError
New submission from Steve Palmer : An io.BUfferedReader object has an (inherited) writable method that returns False. io.IOBase states in the description of the writable method that "If False, write() and truncate() will raise OSError." However, if the BufferedReader object is constructed from a writabe io.RawIOBase object, then the truncate does not raise the exception. >>> import io >>> import tempfile >>> rf = tempfile.TemporaryFile(buffering=0) >>> rf <_io.FileIO name=3 mode='rb+' closefd=True> >>> bf = io.BufferedReader(rf) >>> bf.writable() False >>> bf.truncate(0) 0 Looking at _pyio.py file, the truncate method in the _BufferedIOMixin wrapper class delegates the truncation to it's raw attribute. If the raw element permits the truncation, then it will proceed regardless of the writable state of the wrapper class. I'd suggest that modifying the truncate method in _BufferedIOMixin to raise OSError (or Unsupported) if not self.writable() could fix this problem. -- components: IO messages: 335132 nosy: steverpalmer priority: normal severity: normal status: open title: io.BufferedReader.writabe is False, but io.BufferedReader.truncate does not raise OSError versions: Python 3.7 ___ Python tracker <https://bugs.python.org/issue35950> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue35869] io.BufferReader.read() returns None
Steve Palmer added the comment: The description of read in io.BufferedReader.read function states "Read and return size bytes, or if size is not given or negative, until EOF or if the read call would block in non-blocking mode." This does mention the non-block mode scenario, but I can't parse this sentence. -- ___ Python tracker <https://bugs.python.org/issue35869> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue35869] io.BufferReader.read() returns None
New submission from Steve Palmer : class io.BufferedIOBase states "In addition, those methods [read(), readinto() and write()] can raise BlockingIOError if the underlying raw stream is in non-blocking mode and cannot take or give enough data; unlike their RawIOBase counterparts, they will never return None." However, class.io.BufferedReader (inheriting from io.BufferedIOBase) *does* return None in this case. Admittedly, io.BufferedReader does says it is overriding the inherited method, but I'm surprised that change in behaviour declared for buffered objects, is reverted to the RarIOBase behaviour on a more specific class. The attached file (a little long - sorry), simulates a slow non-blocking raw file, which it wraps in a BufferReader to test the behaviour defined in BufferedIOBase. -- files: read2.py messages: 334630 nosy: steverpalmer priority: normal severity: normal status: open title: io.BufferReader.read() returns None type: behavior versions: Python 3.7 Added file: https://bugs.python.org/file48091/read2.py ___ Python tracker <https://bugs.python.org/issue35869> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue35848] readinto is not a method on io.TextIOBase
Steve Palmer added the comment: I don't have a "real" use case. I discovered the issue when I was developing a unittest suite for what it means to be "file-like". I've been codifying the description in the standard library and exercising my tests against the built-in file-likes, such as the io.StringIO class, when it raised the Attribute Exception. The more I think about it, the more like a documentation problem it feels. For example, the statement "... because their signatures will vary ..." does not apply to readinto in the cases where it is defined. For completeness, the note in io.TextIOBase stating "There is no readinto() method because Python’s character strings are immutable." would also need to be removed as part of a documentation fix. (It's also nice when solutions result in less "stuff". :-) -- ___ Python tracker <https://bugs.python.org/issue35848> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue35848] readinto is not a method on io.TextIOBase
Steve Palmer added the comment: I agree with Karthikeyan that the method does not apply in the io.TextIOBase class context. I'm sorry that I didn't spot the note in the description of io.TextIOBase - though I think that it is easy to miss. I'd suggest that there are two ways to clear this up: 1. change only the documentation to read "Even though IOBase does not declare read() or write() because their signatures will vary, implementations and clients should consider those methods part of the interface." (deleting reference to readinto()) 2. change the standard library for io.TextIOBase to add a method readinto which will raise an UnsupportedOperation. With option 1, the descriptions for io.RawIOBase and io.BufferedIOBase both include description of the readinto method, so nothing is lost by removing mention of it at the io.IOBase level of the hierarchy. In any case, readinto() is not defined on the io.IOBase class. >>> 'readinto' not in dir(io.IOBase) True With option 2, it feels like this is closer to the design intent of a common interface over similar but distinguished classes. It also avoids removing things from the documentation in case someone already has some expectations of the behaviour. -- ___ Python tracker <https://bugs.python.org/issue35848> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue35848] readinto is not a method on io.TextIOBase
New submission from Steve Palmer : class io.IOBase states "Even though IOBase does not declare read(), readinto(), or write() because their signatures will vary, implementations and clients should consider those methods part of the interface. Also, implementations may raise a ValueError (or UnsupportedOperation) when operations they do not support are called." However, even though class io.TextIOBase is described as inheriting from io.IOBase, a call to readinto method returns AttributeError exception indicating no readinto attribute, inconsistent with the documentation. -- components: IO messages: 334507 nosy: steverpalmer priority: normal severity: normal status: open title: readinto is not a method on io.TextIOBase type: behavior versions: Python 3.7 ___ Python tracker <https://bugs.python.org/issue35848> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
