lsst.skymap  16.0-1-g4515a79+5
cachingSkyMap.py
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1 #
2 # LSST Data Management System
3 # Copyright 2008-2012 LSST Corporation.
4 #
5 # This product includes software developed by the
6 # LSST Project (http://www.lsst.org/).
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22 
23 from .baseSkyMap import BaseSkyMap
24 
25 __all__ = ["CachingSkyMap"]
26 
27 
29  """A SkyMap that generates its tracts on request and caches them
30 
31  A subclass should define
32  * __init__ to calculate the required number of tracts (and pass it up)
33  * generateTract to generate a tract
34 
35  Subclassers should also check that the arguments to the constructor are
36  consistent with the below __reduce__ method.
37  """
38 
39  def __init__(self, numTracts, config=None, version=0):
40  super(CachingSkyMap, self).__init__(config)
41  self._numTracts = numTracts
42  self._tractCache = [None] * self._numTracts
43  self._tractInfo = None # We shouldn't need this; we will generate tracts on demand
44  self._version = version
45 
46  def __reduce__(self):
47  """To support pickling
48 
49  Warning: This method assumes that the constructor should be defined:
50  __init__(self, config, version=defaultVersion)
51  The use of 'config' is effectively set by the registry mechanism.
52  If additional optional arguments are added, this method should be
53  overridden to correspond.
54  """
55  return (self.__class__, (self.config, self._version))
56 
57  def __iter__(self):
58  """Iterator over tracts"""
59  for i in range(self._numTracts):
60  yield self[i]
61 
62  def __len__(self):
63  """Length is number of tracts"""
64  return self._numTracts
65 
66  def __getitem__(self, index):
67  """Get the TractInfo for a particular index
68 
69  The tract is returned from a cache, if available, otherwise generated
70  on the fly.
71  """
72  if index < 0 or index > self._numTracts:
73  raise IndexError("Index out of range: %d vs %d" % (index, self._numTracts))
74  if self._tractCache[index] is not None:
75  return self._tractCache[index]
76  tract = self.generateTract(index)
77  self._tractCache[index] = tract
78  return tract
79 
80  def generateTract(self, index):
81  """Generate the TractInfo for the particular index"""
82  raise NotImplementedError("Subclasses must define this method.")
def __init__(self, numTracts, config=None, version=0)