[Python-Dev] Pre-PEP: Allow Empty Subscript List Without Parentheses (original) (raw)

Tim Hochberg tim.hochberg at ieee.org
Fri Jun 9 20:09:22 CEST 2006

Guido van Rossum wrote:

On 6/9/06, Nicko van Someren <nicko at nicko.org> wrote: [...]

The language doesn't have zero-dimensional arrays, although it doesn't prevent users from defining them. but why would one want to index a zero-dimensional array, since it has no dimensions? It should be written as x, not x[].

In Numpy, a 0-D array [for example, array(5)] is almost, but not quite, equivalent to scalar [for example, 5]. The difference is that the former is mutable. Thus "a[()] = 3" will set the value of a 0-D array to 3 and "a[()]" will extract the current, scalar value of a, for instance if you need a hashable object.

Whether that makes x[] desirable I won't venture an opinion. I don't see a lot of use of 0-D arrays in practice.

[...]

-tim

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