Numeric/Numarray equivalent to zip ?

[Peter Otten]

George Sakkis wrote:

> Though not the fastest to execute; using concatenate instead of
> initializing an array from a list [a,a] is more than 2,5 time faster in
> my system (~4.6 vs 11.8 usec per loop according to timeit.py), and it's
> not harder either. 

That surprises me. I would expect essentially the same amount of
data-shuffling.

> One difference is that the equivalent expression for 
> concatenate expects arrays of shape (1,len(a)) instead of 1D arrays os
> shape (len(a),):

If you want to start out with 1D arrays, just reorder the operations: 

>>> a = array(range(5))
>>> reshape(concatenate((a, a)), (2, 5))
array([[0, 1, 2, 3, 4],
       [0, 1, 2, 3, 4]])
>>>

Peter