import collections
# from jaraco.collections 3.3
class FreezableDefaultDict(collections.defaultdict):
"""
Often it is desirable to prevent the mutation of
a default dict after its initial construction, such
as to prevent mutation during iteration.
>>> dd = FreezableDefaultDict(list)
>>> dd[0].append('1')
>>> dd.freeze()
>>> dd[1]
[]
>>> len(dd)
1
"""
def __missing__(self, key):
return getattr(self, '_frozen', super().__missing__)(key)
def freeze(self):
self._frozen = lambda key: self.default_factory()
class Pair(collections.namedtuple('Pair', 'name value')):
@classmethod
def parse(cls, text):
return cls(*map(str.strip, text.split("=", 1)))
