> import bidict
> dir(bidict)
['MutableMapping', '_LEGALNAMEPAT', '_LEGALNAMERE', '__builtins__', '__doc__', '__file__', '__name__', '__package__', 'bidict', 'inverted', 'namedbidict', 're', 'wraps']
 

> from bidict import bidict
> D=bidict({'a':'b'})
> D['a']
'b'
> D[:'b']
'a'
> ~D        #反转字典
bidict({'b': 'a'})
> dict(D)    #转为普通字典
{'a': 'b'}
> D['c']='c'   #添加元素，普通字典的方法都可以用
> D
bidict({'a': 'b', 'c': 'c'}) 

> seq = [(1, 'one'), (2, 'two'), (3, 'three')]
> list(inverted(seq))
    [('one', 1), ('two', 2), ('three', 3)]

> CoupleMap = namedbidict('CoupleMap', 'husbands', 'wives')
> famous = CoupleMap({'bill': 'hillary'})
> famous.husbands['bill']
'hillary'
> famous.wives['hillary']
'bill'
> famous.husbands['barack'] = 'michelle'
> del famous.wives['hillary']
> famous
CoupleMap({'barack': 'michelle'})

> HTMLEntities = namedbidict('HTMLEntities', 'names', 'codepoints')
> entities = HTMLEntities({'lt': 60, 'gt': 62, 'amp': 38}) # etc
> entities.names['lt']
60
> entities.codepoints[38]
'amp'

> import bidict
> from bidict import bidict
> husbands2wives = bidict({'john': 'jackie'})
> ~husbands2wives
bidict({'jackie': 'john'})

> import bidict
> from bidict import bidict
> husbands2wives = bidict({'john': 'jackie'})
> ~husbands2wives
bidict({'jackie': 'john'})

> (~bi)['one']
1

> seq = [(1, 'one'), (2, 'two'), (3, 'three')]
> list(inverted(seq))
[('one', 1), ('two', 2), ('three', 3)]

> bi == bidict({1:'one'})
> bi == dict([(1, 'one')])
True

> bi.get('one')
1
> bi.setdefault('one', 2)
1
> bi.setdefault('two', 2)
2
> len(bi) # calls __len__
2
> bi.pop('one')
1
> bi.popitem()
('two', 2)
> bi.inv.setdefault(3, 'three')
'three'
> bi
bidict({'three': 3})
> [key for key in bi] # calls __iter__, returns keys like dict
['three']
> 'three' in bi # calls __contains__
True
> list(bi.keys())
['three']
> list(bi.values())
[3]
> bi.update([('four', 4)])
> bi.update({'five': 5}, six=6, seven=7)
> sorted(bi.items(), key=lambda x: x[1])
[('three', 3), ('four', 4), ('five', 5), ('six', 6), ('seven', 7)]