Question

The textbook examples of multiple unpacking assignment are something like:

import numpy as NP
M = NP.arange(5)
a, b, c, d, e = M
# so of course, a = 0, b = 1, etc.

M = NP.arange(20).reshape(5, 4)     # numpy 5x4 array
a, b, c, d, e = M
# here, a = M[0,:], b = M[1,:], etc. (ie, a single row of M is assigned each to a through e)

(My question is not numpy specific. Indeed, I would prefer a pure Python solution.)

For the piece of code I’m looking at now, I see two complications on that straightforward scenario:

• I usually won’t know the shape of M; and

• I want to unpack a certain number of
  items (definitely less than all items), and
  I want to put the remainder into a single
  container

So back to the 5×4 array above, what I would very much like to do is assign the first three rows of M to a, b, and c respectively (exactly as above), and the rest of the rows (I have no idea how many there will be, just some positive integer) to a single container, all_the_rest = [].

Answer 1

Python 3.x can do this easily:

a, b, *c = someseq

Python 2.x needs a bit more work:

(a, b), c = someseq[:2], someseq[2:]