Python 排序字典的 key

Question

if __name__ == '__main__':
    students = [('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]
    print sorted(students,key=lambda x: x[2])

    a=dict(a='1',b='2',e='5',c='3')
    sort = ['c','b','a','e']

    print sorted(a,key=lambda x:  (x in sort and sort.index(x),a[x]) )

    # 按照数组 sort 里面定义的顺序排序 a 的 key
    dict = sorted(a.iteritems(), key=lambda d: (d[0] in sort and sort.index(d[0])), reverse=False)
    print dict