Mailman 3 unpacking in index expression - Python-ideas

April 6, 2016


      I was trying to unpack an array or tuple in index expression (python
3.5.1) but this failed.
I think for consistency of language use it would be desirable to allow
that as well.  Below an example of my attempt indexing a numpy array,
x:
...
...
...
import numpy as np
x = np.arange(12).reshape(3,-1)
x[*[0,1]]
    x[*[0,1]]
      ^
SyntaxError: invalid syntax
...
...
...
x[*(0,1)]
    x[*(0,1)]
      ^
SyntaxError: invalid syntax
for the case of numpy, the latter works as intended w/o unpacking
...
...
...
x[(0,1)]
 1
which is equivalent to the desired behaviour of unpacking
...
...
...
x[0,1]
 1
but for the list case the behaviour is different (as intended by design)
...
...
...
x[[0,1]]
array([[0, 1, 2, 3],
       [4, 5, 6, 7]])
My proposal hence is to allow unpacking in index expressions as well.
I do not have a use case for dictionary / keyword unpacking; this
would look awkward anyway.

-Alexander

unpacking in index expression

Alexander Heger

Serhiy Storchaka

Serhiy Storchaka

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