python 多关键字排序_用Python排序字典

﹏ヽ暗。殇╰゛Y 2023-02-28 08:43 27阅读 0赞

python 多关键字排序

## 介绍 **(****Introduction****)** ##

In this tutorial, we are going to take a look at the various ways following which we can **Sort a Dictionary in Python**.

在本教程中，我们将研究可以**用Python排序字典**的各种方式。

In Python, a [Dictionary][] is a collection of key-value pairs. The sequence of such **key** and **value** pairs is separated by commas. These pairs are called **items**.

在Python中， [字典][Dictionary]是键值对的集合。 这样的**键**和**值**对的顺序以逗号分隔。 这些对称为**项** 。

## 用Python对字典进行排序的不同方法 **(****Different Ways to sort a Dictionary in Python****)** ##

As mentioned above, a dictionary item consists of a key and its corresponding value. Hence, sorting for a dictionary can be performed by using any one of the **key** or **value** parts as a parameter.

如上所述，字典项由键及其对应的值组成。 因此，可以通过使用**键**或**值**部分中的任何一个作为参数来执行字典的排序。

So, let us now take a look at the different methods by which we can sort a dictionary **by key** or **by value**.

因此，现在让我们看一下可以**通过键**或**值**对字典**进行**排序的不同方法。

### 1.按关键字排序字典 **(****1. Sort Dictionary by Key****)** ###

We can directly sort a dictionary using the built-in `sorted()` method in Python. This can be done by passing the dictionary itself and a function that specifies the parameter on the basis of which the sorting is to be done(in this case key).

我们可以使用Python中内置的`sorted()`方法直接对字典进行`sorted()` 。 这可以通过传递字典本身和一个函数来完成，该函数指定要基于其进行排序的参数（在本例中为键）。

Let us see how.

让我们看看如何。

d = { 5: 1 , 4: 2 , 3: 3 , 2: 4 , 1: 5 }
    
    print("The original dictionary: ", d)
    
    #sorting by key
    a = dict(sorted(d.items(), key=lambda x: x[0]))
    
    print("After sorting by key: ", a)

**Output:**

**输出：**

The original dictionary:  {5: 1, 4: 2, 3: 3, 2: 4, 1: 5}
    After sorting by key:  {1: 5, 2: 4, 3: 3, 4: 2, 5: 1}

Here,

这里，

*  The `d.items()` method returns a list of tuples(items) containing the **keys** and their corresponding **values**,
    
    `d.items()`方法返回一个元组（items）列表，其中包含**键**及其对应的**值** ，
 *  The `lambda` function returns the key(**0th** element) for a specific item tuple,
    
    `lambda`函数返回特定项目元组的key（ **第0个**元素），
 *  When these are passed to the `sorted()` method, it returns a sorted sequence which is then type-casted into a dictionary.
    
    当这些参数传递给`sorted()`方法时，它返回排序的序列，然后将其类型转换为字典。

Remember, this method can be used in **Python 3.6+** versions as it considers dictionaries as ordered sequences. For older versions, we can replace the lambda function with the `itemgetter()` method from the **operator** module. Let us see how.

请记住，此方法可在**Python 3.6+**版本中使用，因为它将字典视为有序序列。 对于较旧的版本，我们可以使用**operator**模块中的`itemgetter()`方法替换lambda函数。 让我们看看如何。

from operator import itemgetter
    
    d = { 5: 1 , 4: 2 , 3: 3 , 2: 4 , 1: 5 }
    print("Original Dict: ", d)
    
    #sorting by key
    s_d = dict(sorted(d.items(), key=itemgetter(0)))
    print("Sorted dict: ", s_d)

**Output:**

**输出：**

Original Dict:  {5: 1, 4: 2, 3: 3, 2: 4, 1: 5}
    Sorted dict:  {1: 5, 2: 4, 3: 3, 4: 2, 5: 1}

Here also the methods`sorted()` and `items()` work the same way. But in place of a **lambda** function, the`itemgetter(0)` method returns a callable object that fetches the **0th** item from its operand using the operand’s `__getitem__()` method. In this case, as we need to sort **by key**, we consider the **0th** element.

这里的`sorted()`和`items()`方法也以相同的方式工作。 但是代替**lambda**函数， `itemgetter(0)`方法返回一个可调用对象，该对象使用操作数的`__getitem__()`方法从其操作数中获取第**0个**项目。 在这种情况下，由于我们需要**按key**排序，因此我们考虑第**0个**元素。

### 2.按值对字典排序 **(****2. Sort a Dictionary by Value****)** ###

Sorting a dictionary by value is similar to sorting by key. The only difference being that this type the parameter on the basis of which the sorting would be done is the **value** part of the corresponding items.

按值对字典进行排序类似于按键对字典进行排序。 唯一的不同是，此类型的参数将根据其进行排序，而该参数是相应项目的**值**部分。

Hence as we did earlier, we can use the `sorted()` method along with a lambda function for **Python 3.6+** versions. Let us see how.

因此，就像我们之前所做的那样，对于**Python 3.6+**版本，我们可以将`sorted()`方法与lambda函数一起使用。 让我们看看如何。

d = { 0: 'd', 1: 'c', 2: 'b', 3: 'a' }
    
    print("The original dictionary: ", d)
    
    #sorting by value
    a = dict(sorted(d.items(), key=lambda x: x[1]) )
    
    print("After sorting by value: ", a)

**Output:**

**输出：**

The original dictionary:  {0: 'd', 1: 'c', 2: 'b', 3: 'a'}
    After sorting by value:  {3: 'a', 2: 'b', 1: 'c', 0: 'd'}

Similarly here, according to the values returned by the **lambda** function(`x[1]` value for an item `x`) the dictionary `d` is sorted.

同样在这里，根据由**lambda**函数（返回的值`x[1]`值的项目`x` ）的字典`d`排序。

Again for older versions of Python follow the below-mentioned method.

同样，对于旧版本的Python，请遵循以下方法。

from operator import itemgetter
    
    d = { 0: 'd', 1: 'c', 2: 'b' , 3: 'a' }
    print("Original Dict: ", d)
    
    #sorting by value
    s_d = dict(sorted(d.items(), key=itemgetter(1)))
    print("Sorted dict: ", s_d)

**Output:**

**输出：**

Original Dict:  {0: 'd', 1: 'c', 2: 'b', 3: 'a'}
    Sorted dict:  {3: 'a', 2: 'b', 1: 'c', 0: 'd'}

Similarly, sorted() along with d.items() and itemgetter(1) methods sort the dictionary d on the basis of value.

类似地，sorted（）连同d.items（）和itemgetter（1）方法根据值对字典d进行排序。

### 3.反向排序 **(****3. Sorting in reverse order****)** ###

The `sorted()` method comes with another argument `reverse`. That can be used for specifying the order in which the sorting is to be done. If passed `True`, the sorting takes place in **reverse** order(descending). And if `False` is passed(default), the sorting takes place in **ascending** order.

`sorted()`方法带有另一个参数`reverse` 。 可以用于指定排序的顺序。 如果通过`True` ，则排序以**相反的**顺序（降序）进行。 如果传递了`False` （默认值），则排序以**升序进行** 。

Let us try to understand this by an example where we try to reverse sort a dictionary by key.

让我们尝试通过一个示例对这种情况进行理解，在该示例中，我们尝试对关键字进行反向排序。

d = { 'a': 23, 'g': 67, 'e': 12, 45: 90}
    
    print("The original dictionary: ", d)
    
    #sorting by value in reverse
    a = dict(sorted(d.items(), reverse = True, key=lambda x: x[1]))
    print("After sorting by value in reverse order: ", a)
    
    #sorting by value in ascending order
    a = dict(sorted(d.items(), key=lambda x: x[1]))#by default reverse is set to False
    print("After sorting by value in ascending order: ", a)

**Output:**

**输出：**

The original dictionary:  {'a': 23, 'g': 67, 'e': 12, 45: 90}
    After sorting by value in reverse order:  {45: 90, 'g': 67, 'a': 23, 'e': 12}
    After sorting by value in ascending order:  {'e': 12, 'a': 23, 'g': 67, 45: 90}

From the above output,it is clear that passing the reverse parameter as `True` the above dictionary is sorted in reverse order(**descending**).

根据以上输出，  显然，将反向字典作为`True`传递给上面的字典是按相反的顺序排序（ **降序** ）。

## 结论 **(****Conclusion****)** ##

So in this tutorial, we learned how we can **sort a dictionary in Python** using various methods.

因此，在本教程中，我们学习了如何使用各种方法**在Python中对字典进行排序** 。

For any further questions, feel free to use the comments below.

如有其他疑问，请随时使用以下评论。

## 参考资料 **(****References****)** ##

*  [How to Sort a Dictionary in Python?][How to Sort a Dictionary in Python] – AskPython Post
    
    [如何在Python中对字典排序？][How to Sort a Dictionary in Python] – AskPython发布
 *  [Python Dictionary][Dictionary] – Journal Dev Post
    
    [Python字典][Dictionary] – Journal Dev Post
 *  [How do I sort a dictionary by value?][How do I sort a dictionary by value] – Stackoverflow Question
    
    [如何按值对字典排序？][How do I sort a dictionary by value] – Stackoverflow问题
 *  [How can I sort a dictionary by key?][How can I sort a dictionary by key] – Stackoverflow Question
    
    [如何按键对字典排序？][How can I sort a dictionary by key] – Stackoverflow问题

> 翻译自: [https://www.journaldev.com/38407/sort-a-dictionary-in-python][https_www.journaldev.com_38407_sort-a-dictionary-in-python]

python 多关键字排序

[Dictionary]: https://www.journaldev.com/14401/python-dictionary
[How to Sort a Dictionary in Python]: https://www.askpython.com/python/dictionary/sort-a-dictionary-in-python
[How do I sort a dictionary by value]: https://stackoverflow.com/questions/613183/how-do-i-sort-a-dictionary-by-value
[How can I sort a dictionary by key]: https://stackoverflow.com/questions/9001509/how-can-i-sort-a-dictionary-by-key
[https_www.journaldev.com_38407_sort-a-dictionary-in-python]: https://www.journaldev.com/38407/sort-a-dictionary-in-python