Python composite data types--tuples, dictionaries

Lists List

Used to store multiple data

Check and delete and change

list ()/list ()

Set Set

Used to store multiple data

Check and delete and change

set ([])/set ()

1. Combination data Type--tuple (tuple)

The meaning of appearance:

In order to show real life, more fixed data, the concept of tuples appeared

The characteristics of the tuple:

You can also store multiple data, but once you declare and assign a value, you are not allowed to modify the data

Tuple's declaration:

Declaration by a pair of parentheses

t = ("Spring", "Summer", "Autumn", "Winter")

Functions that appear in tuples:

COUNT (): Query the number of occurrences of the specified data

Index (): query where the specified data appears

Note: Declare a tuple that contains only one integer and an empty tuple

L Declare a tuple that contains only one integer, remember x = (12,)

L Declare an empty tuple that can be used directly (), such as: x = ()

L tuple () can be used to declare a tuple and also to convert other combinations of types to infinitesimal groups

Interview question: The data in the tuple is not to be changed. I can change the data, please try to explain

>>> a = ([1,2], [1,2])

>>> A

([1, 2], [1, 2])

>>> A[0][0] = 10

>>> A

([10, 2], [1, 2])

2. Combination data Type--dictionary

Typically, in a list of data, multiple data is present, and multiple data (each of which is not very clear) must have a good convention to use this data without confusion.

Pets = [100, 12]# pet life, pet type

It's a very unfriendly way.

At this time, the dictionary was born

In a dictionary, you can also represent more than one data, but you can add a variable name to each data, and you can use the corresponding variable value by using the variable name

Pets = {"MaxAge": +, "PetType": 12}

Dictionary additions and deletions to check operations

Add Data:

p["Name" = value

modifying data

p["Name" = value

Querying data

x = p["name"]

x = P.get ("name")

x = P.get ("name", info)

Delete data

D.pop (Key)

The characteristics of the dictionary:

The data that is stored is a key value pair {Key:value}

Key cannot be repeated

Value can be repeated

{"Henan": "Region", "Yu": "Region"}

Dictionary in other languages, there is a special name: Map (map)

Dictionary--User management system

The user management system in the list implementation is not the user, but the user name.

Using a dictionary to implement a user management system "is the user information to be managed in the list"

User Information "account number, password, nickname, age, sex, personal introduction"

{"username": "admin", "userpass": "Admin", "nickname": "Rhubarb", "sex": "Male", "Intro": "My Big Face"}

• When new users are added

Account + password + nickname, must be entered

Gender + personal Introduction, you can not enter, data update to "pending"

L User Perfect Personal data

Show user Information

Require the user to enter the name to be modified "sex"

And make changes to the data.

L Delete Users

Require user to enter account + password, correct case, delete user

Query users, traverse the list, query and user input account has been the user's dictionary, display user data