Re: at what complexity, a comparison fails ?

Stef Mientki wrote:
hello,

I had a program that worked perfectly well.
In this program modules were dynamically added,
just by putting the file in a predefined directory.

Now one of the interface mechanisms was to see if some parameter was changed in a an instance,
by comparing the value from the instance with its previous value

This went all well, untill I added a too complex variable,
then the program stopped working, without generating exceptions.

So it seems that comparing a too complex value isn't allowed.
the variable was something like:

A = [ <ndarray>, <ndarray>, ..., [<color>,<color>,...], [<float>, <float>, ... ] ]

So what I need was something like:
if A != A_prev :
... do something
A_prev = A

And this crashes, or at least it doesn't work but also doesn't generate exceptions.
It does seems to work, if A only contains 1 array.

Why am I not allowed to compare A and A_prev ??
And in general, how complex might a list be to make a valid comparison,
or what are the rules ?

I suspect that some of the objects in A have either undefined (or ill-defined) comparison methods, so that the overall list comparison does not do what you expect. I'm not sure what ndarray and color are, but check their comparison methods (you know, __cmp__, __lt__, __eq__, etc). (If that isn't clear, please see http://effbot.org/pyref/__lt__.htm.)

--Hans
.