Python Learning--list

Definitions: 1. Lists are composed of elements arranged in a series of specific order, which can contain letters, numbers, or anything added to a list.

2. The identification symbol for the list is [], and the function name is List

3. The list is ordered

Related concepts:

Elements: Values in a list are called elements, and elements are separated by commas

Subscript: A subscript for each element in the list, starting from left to right from 0, or starting from right to left-1

I. Simple operation of the list

1. Create an empty list

Lists = [] or lists = List ()

2. Create a list with several elements

Lists = [1,2,3,4,5,6,7,8] #创建一个包含数字1-9 of the list called lists

3. Accessing list elements

Print (lists[4]) #lists列表中包含八个元素, subscript from left to right is 0-7, prints the list element labeled 4

4. Modifying list elements

LISTS[8] = 9 #将下标为8 element changed to value 9

Two. List simple operation

1. Adding between the lists

List_1 = [' A ', ' B ', ' C ', ' d ']

List_2 = [' E ', ' f ', ' g ', ' H ']

#定义俩个列表list_1和list_2

#将俩个列表相加

Print (list_1 + list_2)

#结果显示为[' A ', ' B ', ' C ', ' d ',' e ', ' f ', ' g ', ' H ']

2. Multiplying the list

Print (List_1 * 2)

#代表列表相乘2次, the essence of the list list_1 assigned a copy, at this time the list_1 element becomes twice times the original

3. Shard operation of the list

Print (lists[::]) #显示列表中所有元素

Print (Lists[:4]) #显示下标为0-3 element, note that the last number is not in the Python value process

Print (List[::2]) #代表间隔俩个取一个数值

Print (Lists[1:5]) #代表取值下标1-5 element with subscript 5 Not on, please note

4. List member detection

If 3 in lists:

Print (' 3 in list ')

5. Sequence functions

Print (len (lists)) #答应列表的长度或者说列表有多少个元素

Print (max (lists)) #打印列表中最大的元素

Print (min (lists)) #打印列表中值最小的元素

Three. Traversal of the list

#定义几个列表

List_1 = [1,2,3,4,5,6,7,8,9]

List_2 = [

[1,2,3,4,5],

[' A ', ' B ', ' C ', ' d ', ' e ']

]

#进行列表的遍历

All elements of the #此次遍历得到列表list_1

For x in list_1:

Print (x)

#遍历列表list-2 of all elements, both methods

#第一种

For a, B in list_2:

Print (A, B)

#第二种

For x in list_2:

For y in x:

Print (y)

Four. List of commonly used function expressions

#定义一个本次操作所需列表nums

Nums = [' Guan Yu ', ' Zhang Fei ', ' Zhao Yun ', ' ma Teng ', ' Jack Huang ']

1.append () Add elements to the end of the list and modify the original list directly

EX:nums.append (' Xu Yu ')--the result shows an element added to the nums list: [' Guan Yu ', ' Zhang Fei ', ' Zhao Yun ', ' ma Teng ', ' Jack Huang ',' Xu Yu ']

2.insert () Add an element at the specified position in the list

EX:nums.insert (2, ' Code Wei ')--the result shows that the Nums list adds the ' Code Wei ' element to the Subscript 2:[' Guan Yu ', ' Zhang Fei ', 'Dian Wei ', ' Zhao Yun ', ' ma Teng ', ' Jack Huang ',　　' Xu Yu ']

3.pop () Deletes the value of the specified element in the list, and returns the deleted element

EX:nums.pop (2)--the result shows that the subscript 2 position element is removed, nums = [' Guan Yu ', ' Zhang Fei ', ' Zhao Yun ', ' ma Teng ', ' Jack Huang ',' Xu Yu ']

If Print (Nums.pop (2)) can get the value of the element deleted by the pop, you can use this value again

4.remove () removes the specified element from the list

EX:nums.remove (' Xu Yu ')--and operations Delete Xu Yu, the original list becomes nums = [' Guan Yu ', ' Zhang Fei ', ' Zhao Yun ', ' ma Teng ', ' Jack Huang ']

5.clear () empty list

EX:nums.clear ()--note that this operation will clear all the elements inside the list nums

6.copy () copy list

Ex:new_nums = Nums.copy ()--This action copies the list nums the elements inside the New_nums list to get a new list

7.count () counts the number of occurrences of an element in a list

EX:var.count (' Zhao Yun ')--this operation gets the number of times that ' Zhao Yun ' appears in the list nums

8.extend () Merge a list into another list

EX:NUMS_EX = Nums.extend ()-This action adds the values from the Nums list to the list NUMS_EX list, and the elements in the NUMS_EX list are the same as the elements in the Nums

9.index () to view the subscript of an element in a list

Ex:print (Nums.index (' Guan Yu '))---print element ' Guan Yu ' in the list of what is the subscript

Reverse operation of the 10.reverse () list

EX:var.reverse ()--and the operation represents the replacement of elements from the Nums list from head to toe, with the effect of: Nums = [' Jack Huang ',' ma Teng ', ' Zhao Yun ',' Zhang Fei ' ,' Guan Yu ')

11.sort () List sorting

Ex:1. Nums.sort () #默认将列表中的值升序, default sort parameter is False

2. Nums.sort (reverse = True) #将列表中的数值降序排列, reverse take the opposite value

3. Nums.sort (key= Lambda x:x%5) #自定义排序

Five. List-derived

#定义俩个列表

Nums = [1,2,3,4,5,6,7,8]

words = [' A ', ' B ', ' C ', ' D ', ' E ', ' F ', ' G ', ' H ']

1. The most basic list derivation

Print ([' * ' + i + ' * ' for I in Nums])

2. List derivation with judging criteria

Print ([A for a in nums if a%2 = = 0])

3. Multi-loop List derivation

print ([Str (s) + '--+ ' + C for S "Nums for C in words])

4. Multi-loop list derivation with judging conditions

Print ([M + '---C for M in Nums for L in words if nums.index[m] = = Words.index[l]])

#注: This is the knowledge I encountered in the study, if the leakage of the wrong solution please point out, thank you very much! But do not like to spray, are to learn!!!

#或者有愿意交流者可邮件往来 ([email protected])

Python Learning--list