译（四十五）-Python字典排序

MWHLS • 2022/01/29 pm1:01 • Python, 计算机语言

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怎么用键排序字典？

How can I sort a dictionary by key?

怎么用键排序字典？

Antony asked:
- 怎么将 {2:3, 1:89, 4:5, 3:0} 转换为 {1:89, 2:3, 3:0, 4:5}？
  我找了些文章，都是用排序操作，但都返回的是元组。

Answers:

NPE - vote: 1158
Python 3.7 前的标准 Python 字典都是无序的。即便键值对已经排好了，存储在字典时也无法保证顺序。
最简单的方式是使用 OrderedDict，它可以存储插入元素的顺序。

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)])

别介意 od 输出的方式，它会按预期那样打印。

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 的用户，需要把 iter.items() 替换为 .items()：

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

James - vote: 482
字典本身是无序的，如果你需要按顺序输出它们，见下面例子：
在 Python 2.4 及以上版本：

mydict = {'carl':40,
        'alan':2,
        'bob':1,
        'danny':3}

for key in sorted(mydict):
  print "%s: %s" % (key, mydict[key])

输出：
```
alan: 2
bob: 1
carl: 40
danny: 3
```
Python 2.4 以下版本：

keylist = mydict.keys()
keylist.sort()
for key in keylist:
  print "%s: %s" % (key, mydict[key])

参考： http://www.saltycrane.com/blog/2007/09/how-to-sort-python-dictionary-by-keys/
Dipu - vote: 305
对于 CPython、PyPy 3.6 以及高于 3.7 版本的 Python 中，能很容易实现：

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

How can I sort a dictionary by key?

Antony asked:
- What would be a nice way to go from {2:3, 1:89, 4:5, 3:0} to {1:89, 2:3, 3:0, 4:5}?
  I checked some posts but they all use the sorted operator that returns tuples.
  怎么将 {2:3, 1:89, 4:5, 3:0} 转换为 {1:89, 2:3, 3:0, 4:5}？
  我找了些文章，都是用排序操作，但都返回的是元组。
Answers:
- NPE - vote: 1158
- Standard Python dictionaries are unordered (until Python 3.7). Even if you sorted the (key,value) pairs, you wouldn\'t be able to store them in a dict in a way that would preserve the ordering.
  Python 3.7 前的标准 Python 字典都是无序的。即便键值对已经排好了，存储在字典时也无法保证顺序。
- The easiest way is to use OrderedDict, which remembers the order in which the elements have been inserted:
  最简单的方式是使用 OrderedDict，它可以存储插入元素的顺序。
- ```
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)])
```
- Never mind the way od is printed out; it\'ll work as expected:
  别介意 od 输出的方式，它会按预期那样打印。
- ```
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
- For Python 3 users, one needs to use the .items() instead of .iteritems():
  对于 Python 3 的用户，需要把 iter.items() 替换为 .items()：
- ```
In [13]: for k, v in od.items(): print(k, v)
....: 
1 89
2 3
3 0
4 5
```
- James - vote: 482
- Dictionaries themselves do not have ordered items as such, should you want to print them etc to some order, here are some examples:
  字典本身是无序的，如果你需要按顺序输出它们，见下面例子：
- In Python 2.4 and above:
  在 Python 2.4 及以上版本：
- ```
mydict = {'carl':40,
        'alan':2,
        'bob':1,
        'danny':3}

for key in sorted(mydict):
  print "%s: %s" % (key, mydict[key])
```
- gives:
  输出：
- ```
alan: 2
bob: 1
carl: 40
danny: 3
```
- (Python below 2.4:)
  Python 2.4 以下版本：
- ```
keylist = mydict.keys()
keylist.sort()
for key in keylist:
  print "%s: %s" % (key, mydict[key])
```
- Source: http://www.saltycrane.com/blog/2007/09/how-to-sort-python-dictionary-by-keys/
  参考： http://www.saltycrane.com/blog/2007/09/how-to-sort-python-dictionary-by-keys/
- Dipu - vote: 305
- For CPython/PyPy 3.6, and any Python 3.7 or higher, this is easily done with:
  对于 CPython、PyPy 3.6 以及高于 3.7 版本的 Python 中，能很容易实现：
- ```
>>> d = {2:3, 1:89, 4:5, 3:0}
>>> dict(sorted(d.items()))
{1: 89, 2: 3, 3: 0, 4: 5}
```