Pythonistas:
If everyone likes this post, then the code is a "snippet" for
community edification. Otherwise, it's a question: How to do this kind
of thing better?
I want a dict() variant that passes these test cases:
map = Map()
assert not(map.has_key('_default'))
map = Map(yo='dude')
assert map['yo'] == 'dude'
assert map.yo == 'dude'
assert None == map['whatever']
assert not(map.has_key('_default'))
map = Map(yo='dude', _default='q')
assert 'q' == map['whatever']
assert not(map.has_key('_default'))
That's like Bunch, but with a default value. (That makes code with
excess if statements less likely.)
So here's the implementation:
def Map(*args, **kwargs):
value = kwargs.get('_default', None)
if kwargs.has_key('_default'): del kwargs['_default']
class _DefMap(dict):
def __init__(self, *a, **kw):
dict.__init__(self, *a, **kw)
self.__dict__ = self
def __getitem__(self, key):
if not self.has_key(key): self[key] = value
return dict.__getitem__(self, key)
return _DefMap(*args, **kwargs)
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