unicode string formatting

Question

I just saw this in a piece of uncommented code. Is there ever a reason to do this?

 new_var = u'%s' % (child.tag)

where child is an instance and tag is an attribute of that instance? It seems like this does it more simply:

 new_var = unicode(child.tag)

Answer 1

They are identical, and it's just a matter of preference. In terms of the Zen of Python and such, there's really not a "better" way as both are explicit in that they are getting a unicode representation of child.tag. Mechanically they do the same thing:

>>> class foo(object):
    def __init__(self, val):
        self.val = val

    def __str__(self):
        return "str: %s" % self.val
    def __unicode__(self):
        return "unicode: %s" % self.val


>>> f = foo("bar")
>>> u'%s' % f
u'unicode: bar'
>>> unicode(f)
u'unicode: bar'
>>> '%s' % f
'str: bar'