How to unpack tuple of length n to m<n variables [duplicate]

I found out that the related PEP3132 gives some examples for Python 2.x as well:

Many algorithms require splitting a sequence in a "first, rest" pair:

first, rest = seq[0], seq[1:]

[...]

Also, if the right-hand value is not a list, but an iterable, it has to be converted to a list before being able to do slicing; to avoid creating this temporary list, one has to resort to

it = iter(seq)first = it.next()rest = list(it)

Other approaches given in the answers to this question:

Function Argument List Unpacking Approach

requires an extra function definition/call:

def unpack(first, *rest):   return first, restfirst, rest = unpack( *seq )

I wonder why it is implemented in unpacking function argument lists but not for normal tuple unpacking.

Generator Approach

Credits. Also requires a custom function implementation. Is a little more flexible concerning the number of first variables.

def unpack_nfirst(seq, nfirst):  it = iter(seq)  for x in xrange(nfirst):    yield next(it, None)  yield tuple(it)first, rest = unpack_nfirst(seq, 1)

The most pythonic would probably be the ones mentioned in the PEP above, I guess?

I may be wrong but as far as I know

a, *b = (1, 2, 3)

is just syntactic sugar for slicing and indexing tuples. I find it useful but not very explicit.

I've got this handy little function:

def just(n, seq):    it = iter(seq)    for _ in range(n - 1):        yield next(it, None)    yield tuple(it)

For example:

a, b, c = just(3, range(5))print a, b, c## 0 1 (2, 3, 4)

also works with less arguments:

a, b, c = just(3, ['X', 'Y'])print a, b, c## X Y ()

In response to the comment, you can also define:

def take2(a, *rest): return a, restdef take3(a, b, *rest): return a, b, restdef take4(a, b, c, *rest): return a, b, rest... etc

and use it like this:

p = (1,2,3)a, b = take2(*p)print a, b## 1 (2, 3)