vector subscripts in Python?

Alexander Schmolck a.schmolck at gmx.net
Thu Jun 12 18:02:15 CEST 2003


beliavsky at aol.com writes:

> Does Python have the equivalent of "vector subscripts" of Fortran 95?
> The code below illustrates what I am looking for -- with better syntax. 
> 
> def subscript(xx,ii):
>     # return the elements in xx subscripted by ii
>     y = []
>     for i in ii: y.append(xx[i])
>     return y
>     
> ii = [0,2]
> xx = [1,4,9]
> print subscript(xx,ii) # returns [1, 9]; in F95, "print*,xx(ii)" is
> analogous

As already pointed out, a list comprehension will do what you want, but since
I find this behavior useful quite often I think wrapping it up in a function
is worthwhile (note that it allows works for dicts and other iterables).

def at(iterable, indices):
    return [iterable[i] for i in indices]

In [5]: at(xx, ii)
Out[5]: [1, 9]

In [6]: at({'a':1, 'b':2}, ['a','b'])
Out[6]: [1, 2]


'as




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