[Python-ideas] unicodedata.itergraphemes (or str.itergraphemes / str.graphemes)

Wed Jul 10 14:04:13 CEST 2013

2013年7月10日 David Kendal <me at dpk.io>
Well, right. I meant “a new type” like dict.keys() and dict.values() are
“view types”
on a dictionary that provide iterator interfaces. This would just be a
“grapheme view” on a string.
i think that’s the way to go. who would want dozens of new functions in
unicodedata?
how about something like the following? it can easily be extended to get a
reverse iterator.
setting its pos and calling find_grapheme or __next__ or previous allows
for bruce’s usecases.
class GraphemeIterator:
 def __init__(self, string, start=0):
 self.string = string
 self.pos = start
 def __iter__(self):
 return self
 def __next__(self):
 _, next_pos, grapheme = self.find_grapheme()
 self.pos = next_pos
 return grapheme
 def previous(self):
 prev_pos, _, grapheme = self.find_grapheme(backwards=True)
 self.pos = prev_pos
 return grapheme
 def find_grapheme(self, i=None, *, backwards=False):
 """finds next complete grapheme in string, starting at position i
 if backwards is not set, finds grapheme starting at i, or the
next one if i is in the middle of one
 if it is set, it finds the grapheme which i points to, even if
that’s the middle.
 if str[i] is the beginning of a grapheme, backwards finds the
one before it.
 """
 if i is None:
 i = self.pos
 ...
 return (start, end, grapheme)
def find_grapheme(string, i, backwards=False):
 """ convenience function for oneshotting it """
 return GraphemeIterator(string, i).find_grapheme(backwards=backwards)
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