Python data structure (2) ------ list, python Data Structure

Python data structure (2) ------ list, python Data Structure

This article will focus on the list and list operations.

2.1 list Functions

2.2 basic list operations

2.3 List Method

 

2.1 list Functions

>>> List ('hello ')

['H', 'E', 'l', L', 'O']

Note: The list function applies to all types of sequences, not just strings.

2.2 basic list operations

2.2.1 changing the list: Element assignment

>>> X = [1, 3, 5]

>>> X [0] = 'A'

>>> X

['A', 3, 5]

Note: you cannot assign values to nonexistent elements, that is, x [0] ~ X [2] exists and can be assigned a value. x [3] does not exist and cannot be assigned a value.

2.2.2 deleting an element

>>> Names = ['jack', 'bob', 'Tom ', 'Alice']

>>> Del names [1]

>>> Names

['Jack', 'Tom ', 'Alice']

2.2.3 multipart assignment

>>> Name = 'Anthony'

>>> Namelist = list (name)

['A', 'n', 't', 'h', 'O', 'n', 'y']

# When the step size is 1, replace the original part location with the value assignment list

>>> Namelist [1: 3] = ['A', 'B', 'C']

['A', 'A', 'B', 'C', 'h', 'O', 'n', 'y']

# When the step size is 2, the length of the value assignment list must be consistent with the number of original partition Elements

>>> Namelist [: 2] = [1, 2, 3]

Traceback (most recent call last ):
File "<stdin>", line 1, in <module>
ValueError: attempt to assign sequence of size 3 to extended slice of size 4

>>> Namelist [: 2] = [1, 2, 3, 5]

>>> Namelist

[1, 'A', 2, 'C', 3, 'O', 5, 'y']

# The multipart operation can delete sequences.

>>> Namelist [1:] = []

>>> Namelist

['A']

2.3 List Method

2.3.1 append

# Append method append a new object to the end of the list;

>>> Lst = ['A', 'B', 4]

>>> Lst. append ('A ')

['A', 'B', 4, 'a']

# Directly modify the original list

2.3.2 count

# Count the number of times an element appears in the list;

>>> Lst. count ('A ')

2

　　　

2.3.3 extend

# The extend method appends multiple values in another sequence at the end of the list;

>>> Lst2 = [1, 2, 3]

>>> Lst. extend (lst2)

>>> Lst

['A', 'B', 4, 'A', 1, 2, 3]

# Unlike cascade operations, the extend method directly modifies the original list, and the "+" Operation returns a new list.

>>> A = ['A', 'A', 'B']

>>> B = [1, 2, 3]

>>> A + B

['A', 'A', 'B', 1, 2, 3]

>>>

['A', 'A', 'B']

2.3.4 index

# The index method is used to find the index location of the first matching item of a value in the list;

>>> Names = ['jack', 'Tom ', 'Alice', 'Rose ', 'timor']

>>> Names. index ('jack ')

0

>>> Names. index ('Sam ')

Traceback (most recent call last ):
File "<stdin>", line 1, in <module>
ValueError: 'Sam 'is not in list

2.3.5 insert

# The insert method is used to insert objects into the list;

>>> Numbers = [1, 2, 3, 4, 5, 6, 7]

>>> Numbers. insert (3, 'A ')

>>> Numbers

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

# You can also perform the multipart operation.

>>> Numbers [3] = ['a']

[, 3, 'A', 'A',]

2.3.6 pop

# The pop method removes an element from the list (the last one by default );

>>> X = [1, 2, 3]

>>> X. pop ()

3

>>> X

[1, 2]

>>> X. pop (0)

1

>>> X

[2]

2.3.7 remove

# The remove method is used to remove the first matching item of a value in the list;

>>> X = ['Alice ', 'tome', 'time', 'jack']

>>> X. remove ('Alice ')

[Tome ', 'time', 'jack']

2.3.8 reverse

# The reverse Method reversely stores the elements in the list;

>>> X = [1, 3, 5]

>>> X. reverse ()

>>> X

[5, 3, 1]

2.3.9 sort

# Sort the sort method in the original position;

>>> X = [4, 6, 9, 7, 8]

>>> X. sort ()

>>> X

[4,6, 7,8, 9]

# The sort method has no return value. Therefore, the return value of y = x. sort () is None.