What is a good way of having several versions of a python module installed in parallell?

[Joel Hedlund]

Hi!

I write, use and reuse a lot of small python programs for variuos purposes in my work. These use a growing number of utility modules that I'm continuously developing and adding to as new functionality is needed. Sometimes I discover earlier design mistakes in these modules, and rather than keeping old garbage I often rewrite the parts that are unsatisfactory. This often breaks backwards compatibility, and since I don't feel like updating all the code that relies on the old (functional but flawed) modules, I'm left with a hack library that depends on halting versions of my utility modules. The way I do it now is that I update the programs as needed when I need them, but this approach makes me feel a bit queasy. It seems to me like I'm thinking about this in the wrong way.

Does anyone else recognize this situation in general? How do you handle it? 

I have a feeling it should be possible to have multiple versions of the modules installed simultaneously, and maybe do something like this: 

mymodule/
+ mymodule-1.1.3/
+ mymodule-1.1.0/
+ mymodule-0.9.5/
- __init__.py

and having some kind of magic in __init__.py that let's the programmer choose version after import:

import mymodule
mymodule.require_version("1.1.3")

Is this a good way of thinking about it? What would be an efficient way of implementing it?

Cheers!
/Joel Hedlund