On 12/12/2011 4:12 AM, Eelco Hoogendoorn wrote:
The above examples are seldom needed in Python because we have one
general method to repeatedly split a sequence into head and tail.
it = iter(iterable) # 'it' now represents the sequenced iterable
head = next(it) # 'it' now represents the tail after removing the head
In other words, next(it) encompasses all of your examples and many more.
Because 'it' is mutated to represent the tail, it does not need to be
rebound and therefore is not.
The question in language design is never 'could we do these things
before'. The answer is obvious: yes our CPUs are turing complete; we can
do anything. The question is; how would we like to do them?
So do you think the new head/tail unpacking features in python 3 are
entirely uncalled for?
No, *target unpacking (singular) is quite useful in specialized cases.
But it is not specifically head/tail unpacking.
>>> a,*b,c = 1,2,3,4,5,6
>>> a,b,c
(1, [2, 3, 4, 5], 6)
>>> *a,b,c = 1,2,3,4,5
>>> a,b,c
([1, 2, 3], 4, 5)
I personally quite like them, but I would like them to be more general.
It already is. The *target can be anywhere in the sequence.
--
Terry Jan Reedy
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