Import Replacement

[Gabriel Genellina]

En Sat, 31 Jan 2009 18:22:54 -0200, Gary Herron  
<gherron at islandtraining.com> escribió:

> James Pruitt wrote:
>> Imagine there are two files horse.py and buffalo.py. horse.py is
>> imported by another file rider.py. Is it possible to make it so that
>> under certain circumstances possibly based on an environment variable
>> or something similar that when rider.py imports horse.py, it actually
>> imports buffalo.py sort of like a behind the scenes replacement so
>> that rider.py needs little, preferably absolutely no modification?
>
> If horse and buffalo have the same interface then try something like  
> this:
>
> if ...:
>   import horse as ridable
> else:
>   import buffalo as ridable
> # Now use ridable as any module...
>
> If each defines a class of its own name, but the classes have identical
> interfaces, then try
>
> if ...:
>   from horse import Horse as Ridable
> else:
>   from buffalo import Buffalo as Ridable
> # Then instantiate
> animal = Ridable(...)

Another alternative, that does not involve changing rider.py, would be to  
rename horse.py -> _horse.py, buffalo.py -> _buffalo.py and write a *new*  
horse.py:

if ...:
   from _horse import *
else:
   from _buffalo import *

Then, rider.py (and all other modules) still says "import horse", but it  
will get one or another depending on the condition.

-- 
Gabriel Genellina