[Python-3000] Automatically invoking str() in str.join()

[Nick Coghlan]

Thomas Wouters wrote:
> It doesn't matter. Either case is confusing, one way or another, as Tim 
> has already argued. Changing it would be a big mistake. If you want me 
> to come with more comprehensive arguments (other than what Tim already 
> covered), please come with more comprehensive arguments *for* the 
> change, too.

What if the join() builtin had a similar signature to min() & max(), and the 
separator was a keyword only argument? Something like:

   def join(*args, **kwds):
       # Need a mutable seq to handle type conversions
       if len(args) == 1:
           seq = list(args[0])  # Single argument handled as iterator
       else:
           seq = list(args)     # Multiple arguments also accepted
       # Check for a custom separator (keyword argument only)
       sep = kwds.pop('sep', '')
       assert not kwds
       assert isinstance(sep, basestring)
       # Check if we want unicode or 8-bit strings
       sep_is_unicode = isinstance(sep, unicode)
       use_unicode = sep_is_unicode or any(isinstance(x, unicode) for x in seq)
       # Convert all items to desired type
       if use_unicode:
           desired = unicode
           if not sep_is_unicode:
               sep = unicode(sep)
       else:
           desired = str
       for i, item in enumerate(seq):
           if not isinstance(item, desired):
               seq[i] = desired(item)
       # Perform the join operation
       return sep.join(seq)

(as with min() and max(), a single argument which is a non-sequence doesn't 
make sense, as it would simply mean that join(x) == x).

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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