python – 从特定键开始迭代有序的dict项

from __future__ import print_function

from collections import OrderedDict
from itertools import dropwhile

d = OrderedDict(zip(['a',range(4)))

for k,v in dropwhile(lambda x: x[0] != 'b',d.items()):
    print(k,v)

输出：

b 1
c 2
d 3

Python 2,避免使用.items()::创建键值列表

for k,d.iteritems()):
    print(k,v)

定时

%timeit
for each in d.items()[d.keys().index('b'):]:
    pass
The slowest run took 5.18 times longer than the fastest. This could mean that an intermediate result is being cached.
100000 loops,best of 3: 3.27 μs per loop

%%timeit
for each in islice(d.iteritems(),d.keys().index('b'),None):
    pass
The slowest run took 5.23 times longer than the fastest. This could mean that an intermediate result is being cached.
100000 loops,best of 3: 3.05 μs per loop

%%timeit
for k,d.iteritems()):
    pass
The slowest run took 4.92 times longer than the fastest. This could mean that an intermediate result is being cached.
100000 loops,best of 3: 2.23 μs per loop