Property testing in lists

[Dan Brown]

Hi there,

I'm a python newbie (my work is mostly in scientific computing, so I use

Matlab for most of my coding needs).

I'd like to be able to identify the indexes of all members of a list
that
have a particular property.  Certainly, there's lots of ways to do it;
here's two examples with testing for being one more than a multiple of
4.

>>> N = [1, 10, 194, 148, -403]
>>> map (lambda x: x[1],filter (lambda x: x[0] % 4 == 1, map (None, N,
range(len(N)))))
[0, 4]
>>> index = []
>>> for i in range (len(N)):
... if (N[i] % 4 == 1):
...  index.append(i)
...
>>> index
[0, 4]

However, these are both much more disgusting than the equivalent Matlab
code: [Lists in Matlab are indexed starting at 1.]

>> N = [1 10 194 148 -403];
>> find (mod (N,4) == 1)

ans =

     1     5

Is there an equivalent form in Python which is pretty like the Matlab
code,
or am I just barking up the wrong tree?

Thanks much!

-dan brown
 danb at alum.mit.edu