Detailed explanation of the use of sort method in python

This article mainly introduces the sort method in python. Friends who need it can refer to the following

The sort() method in Python is used for array sorting. This article explains it in detail in the form of examples:

1. Basic form
The list has its own sort method, which sorts the list in-place. Since it is in-place sorting, it is obvious that the tuple cannot have this method, because the tuple Groups cannot be modified.

x = [4, 6, 2, 1, 7, 9]
x.sort()
print x # [1, 2, 4, 6, 7, 9]

If you need a sorted copy while keeping the original list unchanged, how to achieve it

x =[4, 6, 2, 1, 7, 9]
y = x[ : ]
y.sort()
print y #[1, 2, 4, 6, 7, 9]
print x #[4, 6, 2, 1, 7, 9]

Note: y = x[:] copies all the elements of the list x to y through the sharding operation. If you simply assign x to y: y = x , y and x still point to the same list, and no new copy is generated.

Another way to get a copy of a sorted list is to use the sorted function:

x =[4, 6, 2, 1, 7, 9]
y = sorted(x)
print y #[1, 2, 4, 6, 7, 9]
print x #[4, 6, 2, 1, 7, 9]

sorted returns an ordered Copy, and the type is always a list, as follows:

print sorted('Python') #['P', 'h', 'n', 'o', 't', 'y']

2. Custom comparison function

You can define your own comparison function and then pass it to the sort method through parameters:

def comp(x, y):
if x < y:
return 1
elif x > y:
return -1
else:
return 0

nums = [3, 2, 8 ,0 , 1]
nums.sort(comp)
print nums # 降序排序[8, 3, 2, 1, 0]
nums.sort(cmp) # 调用内建函数cmp ，升序排序
print nums # 降序排序[0, 1, 2, 3, 8]

3. Optional parameters

The sort method also has two optional parameters: key and reverse

1. When using key, you must provide a function that is called by the sorting process:

x = ['mmm', 'mm', 'mm', 'm' ]
x.sort(key = len)
print x # ['m', 'mm', 'mm', 'mmm']

2. To reverse sort in descending order, you need to provide a Boolean value:

y = [3, 2, 8 ,0 , 1]
y.sort(reverse = True)
print y #[8, 3, 2, 1, 0]

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