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

Question

In Python 3 I can do the following (see also PEP3132 on Extended Iterable Unpacking):

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

What can I do to achieve the same similarly elegant in Python 2.x?

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I know that I could use single element access and slicing operations, but I wonder if there is a more pythonic way. My code so far:

a, b = (1, 2, 3)[0], (1, 2, 3)[1:] # a = 1; b = (2, 3) 

Answer 1

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) 

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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, rest first, 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) 

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

Answer 2

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.