Question

I’m debugging from the python console and would like to reload a module every time I make a change so I don’t have to exit the console and re-enter it. I’m doing:

>>> from project.model.user import *
>>> reload(user)

but I receive:

>>>NameError: name 'user' is not defined

What is the proper way to reload the entire user class? Is there a better way to do this, perhaps auto-updating while debugging?

Thanks.

Answer 1

As asked, the best you can do is

>>> from project.models.user import *
>>> import project # get module reference for reload
>>> reload(project.models.user) # reload step 1
>>> from project.models.user import * # reload step 2

it would be better and cleaner if you used the user module directly, rather than doing import * (which is almost never the right way to do it). Then it would just be

>>> from project.models import user
>>> reload(user)

This would do what you want. But, it’s not very nice. If you really need to reload modules so often, I’ve got to ask: why?

My suspicion (backed up by previous experience with people asking similar questions) is that you’re testing your module. There are lots of ways to test a module out, and doing it by hand in the interactive interpreter is among the worst ways. Save one of your sessions to a file and use doctest, for a quick fix. Alternatively, write it out as a program and use python -i. The only really great solution, though, is using the unittest module.

If that’s not it, hopefully it’s something better, not worse. There’s really no good use of reload (in fact, it’s removed in 3.x). It doesn’t work effectively– you might reload a module but leave leftovers from previous versions. It doesn’t even work on all kinds of modules– extension modules will not reload properly, or sometimes even break horribly, when reloaded.

The context of using it in the interactive interpreter doesn’t leave a lot of choices as to what you are doing, and what the real best solution would be. Outside it, sometimes people used reload() to implement plugins etc. This is dangerous at best, and can frequently be done differently using either exec (ah the evil territory we find ourselves in), or a segregated process.