7.字典的转换:
dict(x=1,y=2) ==> {'y': 2, 'x': 1}
dict([(i,element) for i, element in enumerate(['one', 'two', 'three'])]) ==> {0: 'one', 1: 'two', 2: 'three'}
dict(zip((0,1),(0,2))) ==> {0: 0, 1: 2}