Python- sort according to a key of the dict in the list

1. List of dict data structure description:

 "trends": [
               {
                    "name": "Rick Gates",
                    "promoted_content": null,
                    "query": "%22Rick+Gates%22",
                    "tweet_volume": 135732,
                    "url": "http://twitter.com/search?q=%22Rick+Gates%22"
               },
               {
                    "name": "#TheBachelorette",
                    "promoted_content": null,
                    "query": "%23TheBachelorette",
                    "tweet_volume": 91245,
                    "url": "http://twitter.com/search?q=%23TheBachelorette"
               },
               {
                    "name": "#KremlinAnnex",
                    "promoted_content": null,
                    "query": "%23KremlinAnnex",
                    "tweet_volume": 42654,
                    "url": "http://twitter.com/search?q=%23KremlinAnnex"
               }]

2. Sorting target:

Sort the elements in trends according to the value of tweet_volume.

3. Implementation code:

The following 4 methods are all possible, the fourth one has better performance

1）trends = sorted(trends,key = lambda e:e['tweet_volume'],reverse = True)
2）trends = sorted(trends,key = lambda e:e.get('tweet_volume'),reverse = True))
3）trends = sorted(trends,key = lambda e:e.__getitem__('tweet_volume'),reverse = True))
4）trends = sorted(trends,key = itemgetter('tweet_volume'),reverse = True)

Description:

1. When I select the key in the dict, I choose an index method like e['tweet_volume']. You can also choose e.get('tweet_volume') or e.__getitem__('tweet_volume') to get the key. Value of
2. By using  operator the itemgetter function of the module  , such data structure can be sorted very easily.from operator import itemgetter

4. Sotred() function prototype:

sorted(iterable[,key][,reverse])

iterable: Variables that need to be sorted (required)

key: specify the sorted element

reverse: specify whether to reverse the order, the default is false

For details, please refer to the previous article: Dist series (1): Sort according to the key and value of the dictionary

5. Lambda: anonymous function, the general form is

lambda arguments: expression

6. Considering that some data is NULL, it needs to be processed in advance:

For an empty tweet_volume set to 0, the complete code:

for item in trends:

    if(item['tweet_volume'] is None):

    item['tweet_volume'] = 0

trends = sorted(trends,key = lambda e:e['tweet_volume'],reverse = True)