Cross-reference 'import' in a class hierarchy

[Marcus Alanen]

>> I continue to be amazed that there's simply no way to say
>> 
>>   import "../foo/ook.py"
>> 
>> as should be possible to implement any well-architected class hierarchy.
>
>  It's simple.  Code should not depend directly on code higher than it in
>the package hierarchy.  If it does (and it isn't one of a few extremely rare
>cases), it is misdesigned.
>
>  Code shallow in the hierarchy should manage required references to objects
>required by code deep in the hierarchy by passing them around explicitly. 
>Any other solution is just bunk.

Could you explain why using import via PYTHONPATH is different than
import via current directory?

E.g define a class in file foobar/t2.py:

class A:
	pass


And then, use it from foobar/test.py:

from foobar import t2 as t1
import t2

print id(t1.A)
print id(t2.A)

Why are the id:s different? That is, why do I get two copies of the A
class?  This leads (IMHO) to the fact that one _never_ should use
"import X", (witness isinstance(t1.A(), t2.A) returning 0...)
everything should go via PYTHONPATH. Which in turn means that
you have to set PYTHONPATH for all programs. ?

Some insight into why this is done as it is would be helpful.

-- 
Marcus Alanen
maalanen at abo.fi