[Tutor] Selecting from list

[Peter Otten]

Hs Hs wrote:

> In the following list, is there a simply way to find element less than 200
> sandwiched between two numbers greater than 1000.
> 
> a = [3389, 178, 2674, 2586, 13731, 3189, 785, 1038, 25956, 33551]
> 
> 
> in a, 178 is between 3389 and 2674.  How this particular list can be
> selected for further processing. (sorry this is not homework question. I
> want to avoid looping, because I have 300K lines to parse through)

I'm afraid you have to use a loop. Give us your solution, and we'll see if 
we can improve it.

As a bonus here's a numpy solution without explicit loops:

>>> a = numpy.array([3389, 178, 2674, 2586, 13731, 3189, 785, 1038, 25956, 
33551])
>>> g = a > 1000
>>> l = a < 200
>>> x = g[:-2] & g[2:] & l[1:-1]
>>> numpy.where(x)[0]+1
array([1])

I'll withhold remarks regarding clarity and predictions regarding 
performance ;)