[Tutor] packing up python code to transfer to another machine

[Chris Fuller]

There are two obvious "gotchas".  One is binary extensions.  If you are using 
modules that are not "pure Python", you will have to find *nux versions for 
your target.

The other problem is impossible to solve in general, but most of the time, 
it's less trouble than the first problem.  Python is a dynamic language.  
Dependencies can be created at runtime (using __import__, exec, or execfile, at 
least), and it's certainly possible to write code that has unpredictable 
dependencies.  Usually, however, the unknown dependency is drawn from a finite 
pool that is predictable.  If you include all the bits that each third party 
modules comes with (and the same for your code, if it does any of these 
tricks), you should be Ok, but you can't prove it without analyzing the code.

If you know the package dependencies (usually documented), you can work with 
that.  matplotlib requires numpy, for instance.  If this isn't enough, there's 
the modulefinder module.  Note that it won't detect dynamic dependencies, so 
you have to know what third party stuff is included, and make sure you include 
all of it (or less, but only if you know what you're doing).  Modulefinder also 
makes a lot of noise, and will include stuff you don't want or need.

Another problem is platform compatibility.  If you rely on the windows API, or 
filesystem idiosyncrasies, like drive letters, you'll have to fix those; but 
these are less surprising and easy to catch.

Cheers


On Wednesday 10 February 2010, dwbarne at earthlink.net wrote:
> I have become a true Pythonaholic. My newest problem is....
> 
> I have a rather large Python code (1.5yrs + developing!) currently running
>  on Windows machines that imports several modules, some from external
>  libraries. It allows the user to easily access MySQL databases and plot
>  selected columns and such.
> 
> I would like to bundle my (code + libraries + modules) and transfer all to
>  a *nix environment, rather than just transferring my code over and then
>  having to download and install all the relevant libraries again.
> 
> Is this possible? I would think so with Python but am not sure.
> 
> Is there a Python package that does this? If so, what?
> 
> Thanks in advance.
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