ref: 4dfb8d3b095c72336614ff6add54cc063321ed50
dir: /extras/interval_map.py/
from bisect import bisect_left, bisect_right
from itertools import izip
class IntervalMap(object):
"""
This class maps a set of intervals to a set of values.
>>> i = IntervalMap()
>>> i[0:5] = "hello world"
>>> i[6:10] = "hello cruel world"
>>> print i[4]
"hello world"
"""
def __init__(self):
"""initializes an empty IntervalMap"""
self._bounds = []
self._items = []
self._upperitem = None
def __setitem__(self, _slice, _value):
"""sets an interval mapping"""
assert isinstance(_slice, slice), 'The key must be a slice object'
if _slice.start is None:
start_point = -1
else:
start_point = bisect_left(self._bounds, _slice.start)
if _slice.stop is None:
end_point = -1
else:
end_point = bisect_left(self._bounds, _slice.stop)
if start_point>=0:
if start_point < len(self._bounds) and self._bounds[start_point]<_slice.start:
start_point += 1
if end_point>=0:
self._bounds[start_point:end_point] = [_slice.start, _slice.stop]
if start_point < len(self._items):
self._items[start_point:end_point] = [self._items[start_point], _value]
else:
self._items[start_point:end_point] = [self._upperitem, _value]
else:
self._bounds[start_point:] = [_slice.start]
if start_point < len(self._items):
self._items[start_point:] = [self._items[start_point], _value]
else:
self._items[start_point:] = [self._upperitem]
self._upperitem = _value
else:
if end_point>=0:
self._bounds[:end_point] = [_slice.stop]
self._items[:end_point] = [_value]
else:
self._bounds[:] = []
self._items[:] = []
self._upperitem = _value
def __getitem__(self,_point):
"""gets a value from the mapping"""
assert not isinstance(_point, slice), 'The key cannot be a slice object'
index = bisect_right(self._bounds, _point)
if index < len(self._bounds):
return self._items[index]
else:
return self._upperitem
def items(self):
"""returns an iterator with each item being
((low_bound, high_bound), value)
these items are returned in order"""
previous_bound = None
for (b, v) in izip(self._bounds, self._items):
if v is not None:
yield (previous_bound, b), v
previous_bound = b
if self._upperitem is not None:
yield (previous_bound, None), self._upperitem
def values(self):
"""returns an iterator with each item being a stored value
the items are returned in order"""
for v in self._items:
if v is not None:
yield v
if self._upperitem is not None:
yield self._upperitem
def __repr__(self):
s = []
for b,v in self.items():
if v is not None:
s.append('[%r, %r] => %r'%(
b[0],
b[1],
v
))
return '{'+', '.join(s)+'}'