Feature Proposal: Sequence .join method

[David Murmann]

Steven Bethard wrote:
> David Murmann wrote:
>> Hi all!
>>
>> I could not find out whether this has been proposed before (there are 
>> too many discussion on join as a sequence method with different 
>> semantics). So, i propose a generalized .join method on all sequences 
>> with these semantics:
>>
>> def join(self, seq):
>>     T = type(self)
>>     result = T()
>>     if len(seq):
>>         result = T(seq[0])
>>         for item in seq[1:]:
>>             result = result + self + T(item)
>>     return result
>>
>> This would allow code like the following:
>>
>> [0].join([[5], [42, 5], [1, 2, 3], [23]])
> 
> I don't like the idea of having to put this on all sequences.  If you 
> want this, I'd instead propose it as a function (perhaps builtin, 
> perhaps in some other module).
> 
> Also, this particular implementation is a bad idea.  The repeated += to 
> result is likely to result in O(N**2) behavior.
> 
> STeVe

Hi and thanks for the fast reply,

i just figured out that the following implementation is probably much 
faster, and short enough to be used in place for every of my use cases:

def join(sep, seq):
     return reduce(lambda x, y: x + sep + y, seq, type(sep)())

so, i'm withdrawing my proposal, and instead propose to keep reduce and 
lambda in py3k ;).

thanks again,
David.