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

[Diez B. Roggisch]

Joel Hedlund wrote:

> 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?

Use setuptools. It can exactly do that - install different versions parallel
as eggs, and with a pre-import require-statment you require the desired
one.

Diez