Python tutorial sorting method resolution by dictionary key or value

Python sorted () Function

The sorted () function sorts all iterable objects

sorted syntax:

sorted(iterable, key=None, reverse=False)

Parameter description:

iterable -Iterable objects.

key -Mainly used for comparison elements, only one parameter, the specific function parameters are taken from the iterable object, specify the iterable object in one element to sort.

reverse -Collation, reverse = True descending, reverse = False ascending (default).

1. Sort the dictionary keys (key)

dir_info= {'a':1,'d':8,'c':3,'b':5}
# Press the dictionary button ( key ) (default from small to large) 
dir_sort = sorted(dir_info.items(),key=lambda x:x[0])
print(dir_sort)

Output:
[('a', 1), ('b', 5), ('c', 3), ('d', 8)]

Direct key sorting of dictionaries

sorted({'a':1,'d':8,'c':3,'b':5}.keys())

2. Sort the dictionary by value (value)

dir_info= {'a':1,'d':8,'c':3,'b':5}
# Press the dictionary button ( key ) (default from small to large) 
dir_sort = sorted(dir_info.items(),key=lambda x:x[1])
print(dir_sort)

Output result
[('a', 1), ('c', 3), ('b', 5), ('d', 8)]

Direct value sorting of dictionaries

sorted({'a':1,'d':8,'c':3,'b':5}.values())

Analysis:

dir_info.items() key and value parameters of the dictionary are obtained

dir_info[0] Indicates sorting by element 1

dir_info[1] Indicates sorting by element 2

For ease of understanding, give another example

person_info = [('zhangsan', ' Male ', 15), ('lisi', ' Male ', 12), ('wangwu', ' Male ', 10),]
person_sort = sorted(person_info, key=lambda x: x[2])
print(person_sort)

Output:
[('wangwu', 'Male', 10), ('lisi', 'Male', 12), ('zhangsan', 'Male', 15)]

Of course, the forms of key are also various
For example:

1. Sort by String Length

key = lambda x:len(x)

2. First follow element 1, then follow element 2:

key = lambda x : (x[0] , x[1])

Extension:

Sort a 1 part of the data in the list as a key (select the element that iconic can be used for sorting as a condition)

list_info = ['test-10.txt','test-11.txt','test-22.txt','test-14.txt','test-3.txt','test-20.txt']
list_sort = sorted(list_info, key=lambda d : int(d.split('-')[1].split('.')[0]))
print(list_sort)

Output result
['test-3.txt', 'test-10.txt', 'test-11.txt', 'test-14.txt', 'test-20.txt', 'test-22.txt']

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