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PyFilesystem
FileWrapper.__del__ doesn't call FileWrapper.close
Not sure if this is a bug or not, but thought I'd report it here in case it is
;)
What steps will reproduce the problem?
>>> from fs.osfs import OSFS
>>> from fs.filelike import FileWrapper
>>> class FileWrapperSub(FileWrapper):
... def __init__(self,wrapped_file,mode=None):
... super(FileWrapperSub,self).__init__(wrapped_file,mode)
... print "file %s was opened" % getattr(self, 'name', '')
... def close(self):
... super(FileWrapperSub,self).close()
... print "file %s was closed" % getattr(self, 'name', '')
...
>>> myfs = OSFS('.')
>>> f = FileWrapperSub(myfs.open('testfile1', 'w'))
file \\?\D:\pyfilesystem\testfile1 was opened
>>> f.write('fish')
>>> f.close()
file \\?\D:\pyfilesystem\testfile1 was closed
>>> FileWrapperSub(myfs.open('testfile2', 'w')).write('cat')
file \\?\D:\pyfilesystem\testfile2 was opened
>>>
What is the expected output? What do you see instead?
I'd expect the last line to print
file \\?\D:\pyfilesystem\testfile2 was opened
file \\?\D:\pyfilesystem\testfile2 was closed
Instead, it doesn't print that the file got closed.
Please use labels and text to provide additional information.
It looks like FileWrapper.__del__ calls close on the base class (in this case
FileLikeBase) and on the wrapped_file, but not on self. However I'm not 100%
certain of what all the code in FileWrapper.__del__ is doing.
Feel free to close this as invalid if I've misunderstood this and the fix is
for FileWrapperSub to simply override __del__ as well.
Original issue reported on code.google.com by [email protected] on 2 Sep 2012 at 5:11
I haven't actually tested this, but I think because you are running this inside
the interpreter that that your FileWrapperSub instance isn't actually going out
of scope there. The interpreter keeps the result of the last command in a
variable called '_', so there is still a reference to it after the last line.
If you put the code in a .py file and run it, I suspect it will work as you
would expect. If it doesn't, then it must be a bug.
Original comment by willmcgugan on 3 Sep 2012 at 9:59
Just tested it, and you're absolutely right, and it does look like __del__
doesn't call close on itself, only on FileWrapperBase and the wrapped file. But
I think this may be intended behaviour. Best to run it by Ryan to be sure.
Original comment by willmcgugan on 3 Sep 2012 at 10:32
IIRC, __del__ bypasses self.close() so that it can be sure that
self.wrapped_file is cleaned up properly, even if there happen to be errors in
the file wrapper itself.
Given that python will close self.wrapped_file when it's garbage collected
anyway, this may not be a valid concern. Just calling self.close() would
certainly simplify the code in FileWrapper.__del__.
Original comment by [email protected] on 3 Sep 2012 at 10:03