Friendsnippets

 1 class itranslate:
 2     """Return items from a sequence, substituting them as specified.
 3 
 4     First c'tor argument `subst` is a dictionary, specifying
 5     substitutions to be applied.  If an item matches a key of the
 6     `subst` dictionary, the associated dictionary value is returned
 7     instead; unless the value is `None`, in which case the item is
 8     skipped altogether.
 9 
10     *Note:* you should use an appropriate `dict`-subclass if you want
11      to translate items which are not immutable.
12     
13     Examples::
14       >>> list(itranslate({0:None, 3:2}, [2,1,0,0,1,3]))
15       [2, 1, 1, 2]
16     """
17     def __init__(self, subst, iterable):
18         self.mappings = subst
19         self.iterable = iter(iterable)
20     def __iter__(self):
21         return self
22     def next(self):
23         while True:
24             next = self.iterable.next()
25             if not self.mappings.has_key(next):
26                 return next
27             translated = self.mappings[next]
28             if translated is None:
29                 # skip this item
30                 continue
31             return translated