Finally, we'll want a way to test whether a file we've opened is closed. Sometimes we'll have a lot of file objects open, and if we're not careful, they won't all be closed. How can we test this?
f = open("bg.txt")
f.closed
# False
f.close()
f.closed
# True
Python file objects have a closed attribute which is True when the file is closed and False otherwise.
By checking file_object.closed, we'll know whether our file is closed and can call close() on it if it's still open.