0bc34e48c6
git-svn-id: http://svn.openlayers.org/trunk/openlayers@11006 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
36 lines
1.1 KiB
Python
36 lines
1.1 KiB
Python
"""
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toposort.py
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Sorts dictionary keys based on lists of dependencies.
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"""
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class MissingDependency(Exception):
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"""Exception raised when a listed dependency is not in the dictionary."""
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class Sorter(object):
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def __init__(self, dependencies):
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self.dependencies = dependencies
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self.visited = set()
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self.sorted = ()
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def sort(self):
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for key in self.dependencies:
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self._visit(key)
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return self.sorted
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def _visit(self, key):
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if key not in self.visited:
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self.visited.add(key)
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if not self.dependencies.has_key(key):
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raise MissingDependency(key)
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for depends in self.dependencies[key]:
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self._visit(depends)
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self.sorted += (key,)
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def toposort(dependencies):
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"""Returns a tuple of the dependencies dictionary keys sorted by entries
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in the dependency lists. Given circular dependencies, sort will impose
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an order. Raises MissingDependency if a key is not found.
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"""
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s = Sorter(dependencies)
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return s.sort()
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