List in Python 3

Some common operators of the list

1. Comparison operators

When there are multiple elements in the list, only the No. 0 element is compared between the lists.

>>> List1 = [1,2]>>> list2 = [2,1]>>> list1 > List2false

2. Logical operators

>>> List1 = [1,2]>>> List2 = [2,1]>>> list3 = [1,2]>>> (List1 < List2) and (List3 & Lt LIST2) True

3. Connection operator

+ Connect operator when acting on list, can only connect the same type of data, List + list, integer + integer, etc.

>>> List1 + list2[1, 2, 2, 1]

4. Repeat operator

* When acting on a list as a repeating operator, you can copy the list to the appropriate number of times.

>>> list1[1, 2]>>> list1 * 2 #将list1复制了两次 [1, 2, 1, 2]>>> list1 *= 2    #可以结合赋值操作符快速完成赋值 >&G T;> list1[1, 2, 1, 2]

　　

5. Member Relationship Operators

>>> List1 = [1,2]>>> 1 in list1    #利用成员关系操作符in判断某个元素是否在列表中True >>> 3 in list1false>>& Gt List2 = [[1,2],3,4]>>> [up] in List2    #in只能判断一个层次的成员关系True >>> 1 in List2    #如果是列表中的列表的元素, In there is no way to Judge False>>> 1 in list2[0] #指定层级就能正确判断到了True

Ii. bif of some lists (built-in functions)

1.count function to calculate the number of occurrences of a parameter in the list.

>>> list4 = [1,2,3,4,4,4,5,5,6,6,6,6]>>> list4.count (4) 3

　　

2.index function that lists the index values of the parameters in the list.

>>> list4 = [1,2,3,4,4,4,5,5,6,6,6,6]>>> list4.index (5)    #如果相同的元素有多个, lists only the index value of the first occurrence of the element 6 > >> List4.index (5,7,9) #index后面还有两个参数用来确定范围, here to find 7 #在第7 between elements in the 7th to 9th element, 5 first occurrence is at the index value 7 position, so return 7

　　

3.reverse function to flip the list.

>>> list4 = [1,2,3,4,4,4,5,5,6,6,6,6]>>> list4.reverse () >>> list4[6, 6, 6, 6, 5, 5, 4, 4, 4, 3, 2, 1]

　　

4.sort function that sorts the elements of the list in the specified way.

>>> list5 = [8,2,1,7,6,4,9,3,5]>>> list5.sort () #参数为空时默认升序排列 >>> list5[1, 2, 3, 4, 5, 6, 7, 8, 9]>>> List5.sort (reverse=true) #reverse =false is the default parameter, which indicates ascending (not descending) arrangement, where false is changed to Ttue and descending >>> list5[9 , 8, 7, 6, 5, 4, 3, 2, 1]

TIPS: Notice the meaning of the value of the assignment symbol in Python

Example by list

>>> List6 = [3,1,4,9,5]>>> list7 = list6[:]    #利用切片方式取出的数据, equivalent to the full copy of the original list >>> list8 = List6    #用赋值符号, equivalent to giving the original variable a new name >>> List6.sort (reverse=true) >>> list6[9, 5, 4, 3, 1]>>> list7    #当原变量的值发生变化时, the copied variable values do not change [3, 1, 4, 9, 5]>>> list8    #新名称指向的值会变化 (because List6 and list8 actually point to the same value) [9, 5, 4, 3, 1]
#在编写程序时, pay attention to the difference.

　　

　　

List in Python 3