First reported on the mailing list.
Attempting to write to a file from the top level of a notebook gives
ValueError: I/O operation on closed file
The problem seems to be that Reinteract thinks that f.write('blah') may modifiy f, so it makes a copy of f before execution. A copy of an open file object, however, is a closed file object, which leads to this error. Assigning this statement to another variable (g = f.write('blah')) gets around this problem.
Perhaps file objects should not be tracked by Reinteract's versioning system. It won't be able to undo the actions to the files in any event. A better work-around in the meantime is to enclose all of the file operations in a block, e.g.
try:
f = file('temp.txt', 'w')
f.write('Blah')
finally:
f.close()
Bonus related bug: Sometimes f = file('temp.txt', 'w'); g = f.write('Blah'); f.close() will not actually modify temp.txt, despite not throwing any errors. I believe this is because a copy of f is made before f.close(), and it is this copy (an already closed file object) that is closed, leaving the original object open, and thus potentially not flushed.
