对简单字典的排序，如d = {'a':2, 'b':23, 'c':5, 'd':17, 'e':1}，按key-value排序，官方有一种传说是最快的方法。
最快方式
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from operator import itemgetter
d = {'a':2, 'b':23, 'c':5, 'd':17, 'e':1}
d2 = sorted(d.iteritems(), key=itemgetter(1), reverse=True)
# d2 = [('b', 23), ('d', 17), ('c', 5), ('a', 2), ('e', 1)]
不同方法比较
另附一些排序方法的测试代码：
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def sbv0(d,reverse=False):
return sorted(d.iteritems(), key=lambda (k,v): (v,k), reverse=reverse)
def sbv1(d,reverse=False):
L = [(k,v) for (k,v) in d.iteritems()]
return sorted(L, key=lambda x: x[1] , reverse=reverse)
def sbv2(d,reverse=False):
return sorted(d.items(), key=lambda x: x[1] , reverse=reverse)
def sbv3(d,reverse=False):
L = ((k,v) for (k,v) in d.iteritems())
return sorted(L, key=lambda x: x[1] , reverse=reverse)
def sbv4(d,reverse=False):
return sorted(d.iteritems(), key=lambda x: x[1] , reverse=reverse)
from operator import itemgetter
def sbv5(d,reverse=False):
return sorted(d.iteritems(), key=itemgetter(1), reverse=True)
D = dict(zip(range(100),range(100)))
from profile import run
run("for ii in xrange(10000): sbv0(D, reverse=True)")
run("for ii in xrange(10000): sbv1(D, reverse=True)")
run("for ii in xrange(10000): sbv2(D, reverse=True)")
run("for ii in xrange(10000): sbv3(D, reverse=True)")
run("for ii in xrange(10000): sbv4(D, reverse=True)")
run("for ii in xrange(10000): sbv5(D, reverse=True)")
比较结果
上面测试代码输出的结果
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1030003 function calls in 5.028 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
10000 0.028 0.000 0.028 0.000 :0(iteritems)
1 0.000 0.000 0.000 0.000 :0(setprofile)
10000 2.648 0.000 4.896 0.000 :0(sorted)
1 0.048 0.048 5.028 5.028 <string>:1(<module>)
1 0.000 0.000 5.028 5.028 profile:0(for ii in xrange(10000): sbv0(D, reverse=True))
0 0.000 0.000 profile:0(profiler)
10000 0.056 0.000 4.980 0.000 sortdict.py:1(sbv0)
1000000 2.248 0.000 2.248 0.000 sortdict.py:2(<lambda>)
1030003 function calls in 4.792 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
10000 0.028 0.000 0.028 0.000 :0(iteritems)
1 0.000 0.000 0.000 0.000 :0(setprofile)
10000 2.324 0.000 4.476 0.000 :0(sorted)
1 0.056 0.056 4.792 4.792 <string>:1(<module>)
1 0.000 0.000 4.792 4.792 profile:0(for ii in xrange(10000): sbv1(D, reverse=True))
0 0.000 0.000 profile:0(profiler)
10000 0.232 0.000 4.736 0.000 sortdict.py:4(sbv1)
1000000 2.152 0.000 2.152 0.000 sortdict.py:6(<lambda>)
1030003 function calls in 4.516 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
10000 0.048 0.000 0.048 0.000 :0(items)
1 0.000 0.000 0.000 0.000 :0(setprofile)
10000 2.132 0.000 4.364 0.000 :0(sorted)
1 0.028 0.028 4.516 4.516 <string>:1(<module>)
1 0.000 0.000 4.516 4.516 profile:0(for ii in xrange(10000): sbv2(D, reverse=True))
0 0.000 0.000 profile:0(profiler)
10000 0.076 0.000 4.488 0.000 sortdict.py:8(sbv2)
1000000 2.232 0.000 2.232 0.000 sortdict.py:9(<lambda>)
2040003 function calls in 9.073 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
10000 0.028 0.000 0.028 0.000 :0(iteritems)
1 0.000 0.000 0.000 0.000 :0(setprofile)
10000 4.524 0.000 8.897 0.001 :0(sorted)
1 0.040 0.040 9.073 9.073 <string>:1(<module>)
1 0.000 0.000 9.073 9.073 profile:0(for ii in xrange(10000): sbv3(D, reverse=True))
0 0.000 0.000 profile:0(profiler)
10000 0.108 0.000 9.033 0.001 sortdict.py:11(sbv3)
1010000 2.340 0.000 2.340 0.000 sortdict.py:12(<genexpr>)
1000000 2.032 0.000 2.032 0.000 sortdict.py:13(<lambda>)
1030003 function calls in 4.664 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
10000 0.004 0.000 0.004 0.000 :0(iteritems)
1 0.000 0.000 0.000 0.000 :0(setprofile)
10000 2.348 0.000 4.548 0.000 :0(sorted)
1 0.024 0.024 4.664 4.664 <string>:1(<module>)
1 0.000 0.000 4.664 4.664 profile:0(for ii in xrange(10000): sbv4(D, reverse=True))
0 0.000 0.000 profile:0(profiler)
10000 0.088 0.000 4.640 0.000 sortdict.py:15(sbv4)
1000000 2.200 0.000 2.200 0.000 sortdict.py:16(<lambda>)
30003 function calls in 0.336 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
10000 0.004 0.000 0.004 0.000 :0(iteritems)
1 0.000 0.000 0.000 0.000 :0(setprofile)
10000 0.204 0.000 0.204 0.000 :0(sorted)
1 0.044 0.044 0.336 0.336 <string>:1(<module>)
1 0.000 0.000 0.336 0.336 profile:0(for ii in xrange(10000): sbv5(D, reverse=True))
0 0.000 0.000 profile:0(profiler)
10000 0.084 0.000 0.292 0.000 sortdict.py:19(sbv5)
扩展排序
对下面字典，按d[key][1] 排序
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d = { 'a1': ['g',6],
'a2': ['e',2],
'a3': ['h',3],
'a4': ['s',2],
'a5': ['j',9],
'a6': ['y',7] }
# L = sorted(d, key=lambda k:d[k][1])
# L = sorted(d, key=lambda k:d[k][0])
L = sorted(d.items(), key=lambda (k, v): v[1])
# L [('a2', ['e', 2]), ('a4', ['s', 2]), ('a3', ['h', 3]), ('a1', ['g', 6]), ('a6', ['y', 7]), ('a5', ['j', 9])]
# 获取排序后的key
map(lambda (k,v): k, L)
# ['a2', 'a4', 'a3', 'a1', 'a6', 'a5']
对一个字典列表，按字典的某个键排序
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from operator import itemgetter
old_list = [{'name':'Homer', 'age':39}, {'name':'Bart', 'age':10}]
newlist = sorted(old_list, key=itemgetter('name'))
# newlist = sorted(old_list, key=lambda k: k['name'])
# newlist = sorted(old_list, key=itemgetter('name'), reverse=True)
# old_list.sort(key=itemgetter('name'))
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