Today I had a strange experience. I have copied some updated py files
(modules) to a directory on a remote server, overwritting the old ones.
The pyc files on the server were older. Many programs are importing
these modules, and most of them are started as background jobs (from
cron). They started to throw all kinds of errors. I checked the py
files, and they did have class definitions inside. However when I tried
to use them I got AttributeError exceptions. Telling that those things
are not in the module.
I checked their contents by importing them, and they were not defined
indeed. Finally I have checked the module.__file__ attributes to see
that they are imported from the right place. The __file__ contained the
path to the compiled pyc file, but the path was correct. So finally I
have deleted all pyc files, and suddenly every program was working
again. (Starting the interpreter again and importing the modules again
did not solve the problem.)
I suspect that there were two (or more) programs starting at the same
time, writting the same pyc file at the same time. It happened with two
modules today. Over the years, I have always copied files to this
server, and let background programs compile the pyc files as needed. I
have never experienced anything like this before, and I cannot reproduce
the error.
The question is this: do you think this could happen? Is it possible
that something else caused the problem? What else could it be? What are
the chances that it will happen again, and how can I prevent it?
Thanks,
Laszlo
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