any() and all() shorthand

Tim Chase python.list at tim.thechases.com
Mon Jan 7 21:47:22 CET 2008


> The idea is a shorthand for reduce.  Here, _next_ meant the next item
> in the iterable c.

You mean like one of these:

   def lookahead(iterator):
     i = iter(iterator)
     x = i.next()
     for item in i:
       yield x, item
       x = item

   def lookahead2(iterator, **kwarg):
     i = iter(iterator)
     if 'initial' in kwarg:
       x = kwarg['initial']
     else:
       x = i.next()
     for item in i:
       yield x, item
       x = item
     if 'last' in kwarg:
       yield x, kwarg['last']

   print 'lookahead()'
   for this, next in lookahead([1,2,3,4,5]):
     print this, next

   print 'lookahead2()'
   for this, next in lookahead2([1,2,3,4,5]):
     print this, next

   print 'lookahead2(initial=42)'
   for this, next in lookahead2([1,2,3,4,5], initial=42):
     print this, next

   print 'lookahead2(last=42)'
   for this, next in lookahead2([1,2,3,4,5], last=42):
     print this, next

   print 'lookahead2(initial=3.14159, last=42)'
   for this, next in lookahead2([1,2,3,4,5],
       initial=3.14159, last=42):
     print this, next


There are some alternate behaviors that can happen at the end 
points, so depending on which behavior you want, the lookahead() 
is cleanest, but doesn't allow you to handle edge cases.  The 
lookahead2() is a little more complex, but allows you to specify 
a first item for pairing (so "next" touches every item in your 
list) or a trailing element (so "this" touches every item).

-tkc









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