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class BiDi:
"""
A wee utility class for keeping bi-directional mappings, like field
constants in protocols. Names are attributes on the object, dict-like
access maps values to names:
CONST = BiDi(a=1, b=2)
assert CONST.a == 1
assert CONST.get_name(1) == "a"
"""
def __init__(self, **kwargs):
self.names = kwargs
self.values = {}
for k, v in kwargs.items():
self.values[v] = k
if len(self.names) != len(self.values):
raise ValueError("Duplicate values not allowed.")
def __getattr__(self, k):
if k in self.names:
return self.names[k]
raise AttributeError("No such attribute: %s", k)
def get_name(self, n, default=None):
return self.values.get(n, default)
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