$ python -mtimeit -s'l=range(1000)' 'l[::-1]'      
    100000 loops, best of 3: 3.05 usec per loop
    $ python -mtimeit -s'l=range(1000)' 'l.reverse()'  
    1000000 loops, best of 3: 0.535 usec per loop
    $ python -mtimeit -s'l=range(1000)' 'a=reversed(l)' 
    1000000 loops, best of 3: 0.39 usec per loop

  >>> reversed([])
  <listreverseiterator object at 0xb73ff7cc>

    >>> xrange(13)[::-1]
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    TypeError: sequence index must be integer, not 'slice'

  >>> list(range(13)[::-1]) == list(xrange(12, -1, -1))
  True

Another I found quite useful: instead of collections.defaultdict, you can use the dict's get() method to set a default value if the key doesn't exist. get() takes the key and a default value, and if the key doesn't exist it creates one with the default value provided.

  a = {}
  a['foo'] = a.get('foo',0) + 1
  # a = {'foo':1}
  a['foo'] = a.get('foo',0) + 1
  # a = {'foo':2}

  >>> from collections import Counter
  >>> c = Counter()
  >>> c['foo']
  0
  >>> c['bar'] +=1
  >>> c['bar']
  1
  >>> 

  occurrences = defaultdict(int)
  digraphs = defaultdict(lambda: defaultdict(int))
  
  prev_ch = None
  for ch in long_text:
    occurrences[ch] += 1
    if prev_ch is not None:
      digraphs[prev_ch][ch] += 1
    prev_ch = ch

  print "Occurrences:"
  for ch, count in sorted(occurrences.iteritems()):
    print "  %s: %i" % (ch, count)

  print "Digraph occurences:"
  for ch1, counts in sorted(digraphs):
    for ch2, count in sorted(counts):
      print "  %s%s: %i" % (ch1, ch2, count)

  >>> 
  >>> class PrefixStr:
  ...   def __init__(self, prefix):
  ...     self.prefix = prefix
  ...   def __getattr__(self, s):
  ...     return self.prefix+s
  ... 
  >>> 
  >>> q = PrefixStr('xyz_')
  >>> 
  >>> { q.height:11, q.width:7, q.depth:3 }
  {'xyz_width': 7, 'xyz_depth': 3, 'xyz_height': 11}
  >>>

Also, 2.7 introduced a couple of cool things in collections: OrderedDict and Counter

He explained why he changed his mind on performance, but not whether or not "dynamic typing = bugs". This would've been interesting to read about from a recent convert.