Python lists (list)

Pythonlisting (list)

The sequence is the most basic data structure in Python. Each element in the sequence is assigned a number-its position, or index, the first index is 0, the second index is 1, and so on.

Python has 6 built-in types of sequences, but the most common are lists and tuples.

Sequences can be performed by operations including indexing, slicing, adding, multiplying, and checking members.

In addition, Python has built-in methods for determining the length of a sequence and determining the maximum and minimum elements.

A list is the most commonly used Python data type and can appear as a comma-separated value within a square bracket.

Data items for a list do not need to have the same type

Create a list by enclosing separate data items separated by commas in square brackets. As shown below:

List1 = ['physics'chemistry', 1997, += [1, 2, 3, 4, 5= ["a""b""C"  "D"];

As with the index of a string, the list index starts at 0. Lists can be intercepted, combined, and so on.

Accessing values in a list

Use the subscript index to access the values in the list, and you can also use square brackets to intercept the characters as follows:

# !/usr/bin/python  = ['physics'chemistry', 1997, += [1, 2, 3, 4, 5, 6, 7 ]; Print "  ", list1[0]print"", List2[1:5]

The result of the above example output:

list1[0]:  physicslist2[1:5]:  [2, 3, 4, 5]

Update list

You can modify or update the list's data items, or you can use the Append () method to add the list items as follows:

#!/usr/bin/pythonList= ['Physics','Chemistry', 1997, 2000];Print "Value available at index 2:"PrintList[2];list[2] = 2001;Print "New value available at index 2:"PrintLIST[2];

Note: We will discuss the use of the Append () method in the following chapters

The result of the above example output:

Value available at index 2 :19972 :2001

To delete a list element

You can use the DEL statement to delete the elements of a list, as in the following example:

# !/usr/bin/python  = ['physics'chemistry', 1997, +]; Print List1; del list1[2]; Print "  "print list1;

The result of the above example output:

['physics'chemistry', 1997,2 : [  'physics'chemistry', 2000]

Note: We will discuss the use of the Remove () method in the following chapters

Python List script operators

The operands of the list to + and * are similar to strings. The + sign is used for the combined list, and the * number is used for repeating lists.

As shown below:

Python expression result description
Len ([1, 2, 3]) 3 length
[1, 2, 3] + [4, 5, 6] [1, 2, 3, 4, 5, 6] combination
[' hi! ']  　    * 4 [' hi! ', ' hi! ', ' hi! ', ' hi! '] Repeat
3 in [1, 2, 3] True whether the element exists in the list
For x in [1, 2, 3]: print x, 1 2 3 iterations

Python list interception

A list of Python instances is captured as follows:

>>> L = ['Google','Runoob','Taobao']>>> l[2]'Taobao'>>> l[-2]'Runoob'>>> l[1:] ['Runoob','Taobao']>>>

Describe:

Python Expression Result Description
L[2] ' Taobao ' reads the third element of the list
L[-2] ' Runoob ' reads the second-to-last element in a list
L[1:] [' Runoob ', ' Taobao '] starting with the second element to intercept a list

Python list Functions & methods

Python contains the following functions:

Serial Number	function
1	CMP (List1, List2) Compare two elements of a list
2	Len (list) Number of list elements
3	Max (list) Returns the maximum value of a list element
4	MIN (list) Returns the minimum value of a list element
5	List (seq) Convert a tuple to a list

Python contains the following methods:

Serial Number	Method
1	List.append (obj) Add a new object at the end of the list
2	List.count (obj) Count the number of occurrences of an element in a list
3	List.extend (seq) Append multiple values from another sequence at the end of the list (extend the original list with a new list)
4	List.index (obj) Find the index position of the first occurrence of a value from the list
5	List.insert (index, obj) Inserting an object into a list
6	List.pop (Obj=list[-1]) Removes an element from the list (the last element by default), and returns the value of the element
7	List.remove (obj) To remove the first occurrence of a value in a list
8	List.reverse () Reverse List of elements
9	List.sort ([func]) Sort the original list

List of Notes

Python creates a two-dimensional list that writes the required parameters to cols and rows

 for inch  for  in range (rows)]

Instance:

 for inch  for  in range (5)]>>> list_2d[0].append (3)>>> list_2d[0].append (5) >>> list_2d[2].append (7)>>>3, 5], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 7], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]

#!/usr/bin/python#-*-coding:utf-8-*-list01= ['Runoob', 786, 2.23,'John', 70.2]list02= [123,'John']Printlist01Printlist02#List InterceptionPrintList01[0]PrintList01[-1]PrintList01[0:3]#Duplicate listPrintLIST01 * 2#list CombinationsPrintLIST01 +list02#Get list lengthPrintLen (list01)#To delete a list elementdelList02[0]Printlist02#whether the element exists in the listPrint 'John' inchlist02#True#Iteration forIinchlist01:PrintI#compare two elements of a listPrintCMP (list01, list02)#list Maximum/minimum valuePrintMax ([0, 1, 2, 3, 4])PrintMin ([0, 1])#convert a tuple to a listAtuple= (1,2,3,4) list03=list (atuple)Printlist03#add a new element at the end of the listList03.append (5)Printlist03#append multiple values from another sequence at the end of the list (extend the original list with a new list)list03.extend (list01)Printlist03#Count the number of occurrences of an element in a listPrintList03.count (1)#find the index position of the first occurrence of a value from the listPrintList03.index ('John')#inserting an object into a listlist03.insert (0,'Hello')Printlist03#removes an element from the list (the last element by default), and returns the value of the elementPrintlist03.pop (0)Printlist03#to remove the first occurrence of a value in a listList03.remove (1)Printlist03#reverse List of elementsList03.reverse ()Printlist03#sort the original listList03.sort ()Printlist03

>>> list4=[123,["das","AAA"],234]>>>List4>>>"AAA" inchList4#in can only judge one level of elementFalse>>>"AAA" inchLIST4[1]#Select a list in the list to determineTrue>>> list4[1][1]'AAA'

Python lists (list)