Question

What is the best way in Python to check if a ZipFile object is not already closed?

For the moment I am doing this in a class:

try:
    self.zf.open(archive_name).close()
except RuntimeError:
    self.zf = zipfile.ZipFile(self.path)

with self.zf.open(archive_name) as f: 
    # do stuff...

Is there a better way?

Answer 1

Internally, there is an open file pointer called fp that get’s cleared on close; you can test for that yourself too:

if not self.zf.fp:
    self.zf = zipfile.ZipFile(self.path)

See the zipfile module source; the open method raises the RuntimeError exception if not self.fp is True.

Note that relying on such internal, undocumented implementations can be hairy; if future implementations change your code will break, perhaps in subtle ways. Make sure you have good test coverage for your project.

Alternatively, you could create a ZipFile subclass and override the .close method to track the state, which would be less at risk of breaking due to internal changes:

class MyZipFile(zipfile.ZipFile):
    closed = False
    def close(self):
        self.closed = True
        super(MyZipFile, self).close()

and

if self.zf.closed:
    self.zf = MyZipFile(self.path)

with thanks to aknuds1 for the suggestion.