Use of Python lists

1. Define the list

>>> List1 = ["Zhang San", "John Doe", "Harry", "Zhao Liu"]

2. List value

>>> print (list1[1])//"1" represents the location of the list, note: The elements in the list are counted from "0"

John doe

>>> print (List1[1:3])//NOTE: The slice value of the list is the one containing "head" without "tail"

[' John Doe ', ' Harry ']

>>> print (list1[-1])//"1" is the last value in the Fetch list

Zhao Liu

>>> print (list1[-2:])//Take back two values

[' Harry ', ' Zhao Liu ']

3. Add a value to the list

>>> list1.append ("Xiaoming")//append append to append the new element to the end of the list

>>> Print (List1)

[' Zhang San ', ' John Doe ', ' Harry ', ' Zhao Liu ', ' xiaoming ']

>>> List1.insert (1, "Xiao Li")//insert is inserted, "1" is the position of the list, the new value will squeeze the original value to the back

>>> Print (List1)

[' Zhang San ', ' Xiao Li ', ' John Doe ', ' Harry ', ' Zhao Liu ', ' xiaoming ']

4. Substitution of list elements

>>> list1[0] = "I"

>>> Print (List1)

[' I ', ' Xiao Li ', ' John Doe ', ' Harry ', ' Zhao Liu ', ' xiaoming ']

5. Delete list elements

>>> List1.remove ("I")

>>> Print (List1)

[' Xiao Li ', ' John Doe ', ' Harry ', ' Zhao Liu ', ' xiaoming ']

>>> del List1[0]

>>> Print (List1)

[' John Doe ', ' Harry ', ' Zhao Liu ', ' xiaoming ']

>>> List1.pop ()//pop () does not specify the element position, the last element of the list is deleted by default

' Xiao Ming '

>>> Print (List1)

[' John Doe ', ' Harry ', ' Zhao Liu ']

6. Find its index position according to the element

>>> Print (List1.index ("Harry"))//index can find the index position of the element

1

>>> Print (List1.index ("Zhao Liu"))

2

7. Number of elements in the statistics list

>>> Print (List1.count ("Zhao Liu"))

1

8. Clear the list

>>> List1.clear ()

>>> Print (List1)

[]

9. List reversal

>>> Print (Mumber)

[1, 2, 3, 4, 5, 6, 7]

>>> mumber.reverse ()//reverse indicates a reversal of the list, that is, reverse

>>> Print (Mumber)

[7, 6, 5, 4, 3, 2, 1]

10. Sorting of list elements

>>> Mumber.sort ()//small to large sort

>>> Print (Mumber)

[1, 2, 3, 4, 5, 6, 7]

11, the extension of the list

>>> mumber2 = [8,9,10]

>>> mumber.extend (Mumber2)//extend that the Mumber2 list is merged into the Mumber list, but the Mumber2 list still exists

>>> Print (Mumber)

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

12. Delete List

>>> del Mumber2

13. Replication of the list

>>> name1 = ["Zhang San", "John Doe"]

>>> name2 = name1.copy ()//copy for replication

>>> Print (name1,name2)

[' Zhang San ', ' John Doe '] [' Zhang San ', ' John Doe ']

Now let's change the elements of name1 and see what happens.

>>> name1[0] = "Harry"

>>> print (name1,name2)//All normal

[' Harry ', ' John Doe '] [' Zhang San ', ' John Doe ']

Then we'll change the initial list and test

>>> name1 = ["Zhang San", ["Harry", "Zhao Liu"], "John Doe"]

>>> name2 = Name1.copy ()

>>> name1[1][0] = "Xiao Ming"

>>> Print (NAME1)

[' Zhang San ', [' xiaoming ', ' Zhao Liu '], ' John Doe ']

>>> print (name2)//We now find that when we change the second-level list, the elements of the name2 list change as we go through the list.

[' Zhang San ', [' xiaoming ', ' Zhao Liu '], ' John Doe ']

Reason: This copy is called a shallow copy, it only copy the first layer, because the second layer of the list does not have a copy of the past, it is in memory is a separate memory pointer, so at copy time just copy the memory pointer.

>>> name1 = [' Zhang San ', ' John Doe ', ' Xiao Ming ', ' Little White ', ' Harry ']

>>> print (Name1[::2])//How to use step slices

[' Zhang San ', ' xiaoming ', ' Harry ']

>>> Print (name1[::])

[' Zhang San ', ' John Doe ', ' xiaoming ', ' Little White ', ' Harry ']

Use of Python lists