Closing a file in a class method __exit__ or __del__?
I want to write a class capable of writing an html file. I now have the following skeleton:
class ColorWheel(object):
def __init__(self, params):
self.params = params
def __enter__(self):
self.f = open('color_wheel.html', 'w')
self._write_header()
return self
def __exit__(self, type_unused, value_unused, traceback_unused):
self._write_footer()
self.f.close()
def wheel(self):
# Code here to write the body of the html file
self.f.write('BODY HERE')
I am using this class:
with ColorWheel(params) as cw:
cw.wheel()
The file is written exactly as I expect. However, when I run this, I get the following error:
Exception ValueError: 'I/O operation on closed file' in <bound method ColorWheel.__del__ of ColorWheel.ColorWheel object at 0x0456A330>> ignored
I am assuming that it is trying to close the file while it is already closed. It's right? If so, what would be the correct way to close the file?
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1 answer
You also have a method __del__
that tries to write to the file after it is closed. When it cw
goes out of scope and clears, the trick is called __del__
and you try to write it to the file at that point.
You can check if the file is already closed with
if not self.f.closed:
# do something with file
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