[Tutor] increment a counter inside generator

[Dave Angel]

On 03/13/2013 03:50 PM, Abhishek Pratap wrote:
> Hey Guys
>
> I might be missing something obvious here.
>
>
> import numpy as np
>
> count = 0
> [ count += 1 for num in np.random.random_integers(1,100,20) if num > 20]
>
>   File "<ipython-input-45-0ba0e51b7644>", line 2
>      [ count += 1 for num in np.random.random_integers(1,100,20) if num > 20]
>               ^
> SyntaxError: invalid syntax
>
>
> Also tried
>     <Missing rest of message>

I can't help with the numpy portion of that, but that's not the correct 
syntax for a list comprehension.  The first item must be an expression, 
and count+=1 is NOT.

You probably want  (untested)
   count = sum([  1 for num in ......])

which will add a bunch of ones.  That will probably give you a count of 
how many of the random integers are > 20.

There also may very well be a function in numpy that would do it in one 
step.  See Oscar's message.

-- 
DaveA