如何按键对字典进行排序?

示例输入:

{2:3, 1:89, 4:5, 3:0}

期望的输出:

{1:89, 2:3, 3:0, 4:5}

当前回答

注意:对于Python 3.7+,请参见此答案

标准Python字典是无序的(直到Python 3.7)。即使对(键,值)对进行了排序,也不能将它们存储在字典中以保持排序。

最简单的方法是使用OrderedDict,它会记住元素被插入的顺序:

In [1]: import collections

In [2]: d = {2:3, 1:89, 4:5, 3:0}

In [3]: od = collections.OrderedDict(sorted(d.items()))

In [4]: od
Out[4]: OrderedDict([(1, 89), (2, 3), (3, 0), (4, 5)])

不要在意od是如何打印出来的;它会像预期的那样工作:

In [11]: od[1]
Out[11]: 89

In [12]: od[3]
Out[12]: 0

In [13]: for k, v in od.iteritems(): print k, v
   ....: 
1 89
2 3
3 0
4 5

Python 3

对于Python 3用户,需要使用.items()而不是.iteritems():

In [13]: for k, v in od.items(): print(k, v)
   ....: 
1 89
2 3
3 0
4 5

其他回答

from operator import itemgetter
# if you would like to play with multiple dictionaries then here you go:
# Three dictionaries that are composed of first name and last name.
user = [
    {'fname': 'Mo', 'lname': 'Mahjoub'},
    {'fname': 'Abdo', 'lname': 'Al-hebashi'},
    {'fname': 'Ali', 'lname': 'Muhammad'}
]
#  This loop will sort by the first and the last names.
# notice that in a dictionary order doesn't matter. So it could put the first name first or the last name first. 
for k in sorted (user, key=itemgetter ('fname', 'lname')):
    print (k)

# This one will sort by the first name only.
for x in sorted (user, key=itemgetter ('fname')):
    print (x)

简单:

d = {2:3, 1:89, 4:5, 3:0}
sd = sorted(d.items())

for k,v in sd:
    print k, v

输出:

1 89
2 3
3 0
4 5

以下是建议解决方案的性能:

from collections import OrderedDict
from sortedcontainers import SortedDict
import json

keys = np.random.rand(100000)
vals = np.random.rand(100000)

d = dict(zip(keys, vals))

timeit SortedDict(d)
#45.8 ms ± 780 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)

timeit sorted(d.items())
#91.9 ms ± 707 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)

timeit OrderedDict(sorted(d.items(), key=lambda x: x[0]))
#93.7 ms ± 1.52 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)

timeit dict(sorted(dic.items()))
#113 ms ± 824 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)

timeit OrderedDict(sorted(dic.items()))
#122 ms ± 2.65 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)

timeit json.dumps(d, sort_keys=True)
#259 ms ± 9.42 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)

如我们所见,格兰特·詹克斯的解决方案是目前为止最快的。

Python字典是无序的。通常,这不是问题,因为最常见的用例是执行查找。

最简单的方法是创建一个集合。OrderedDict以排序顺序插入元素。

ordered_dict = collections.OrderedDict([(k, d[k]) for k in sorted(d.keys())])

如果需要迭代,就像上面其他人建议的那样,最简单的方法是迭代排序的键。的例子,

按键排序打印值:

# create the dict
d = {k1:v1, k2:v2,...}
# iterate by keys in sorted order
for k in sorted(d.keys()):
    value = d[k]
    # do something with k, value like print
    print k, value

获取按键排序的值列表:

values = [d[k] for k in sorted(d.keys())]

最简单的解决方案是,你应该得到一个dict键排序顺序的列表,然后遍历dict。例如

a1 = {'a':1, 'b':13, 'd':4, 'c':2, 'e':30}
a1_sorted_keys = sorted(a1, key=a1.get, reverse=True)
for r in a1_sorted_keys:
    print r, a1[r]

以下是输出(按顺序排列)

e 30
b 13
d 4
c 2
a 1