dictionary in python

Dictionary: an associative array or hash table, an object indexable by keyword.
Purpose of dictionary: Define an object that can contain multiple named fields, and can also be used as a container to quickly find unordered data
Dictionaries are the most complete data type in Python and are most commonly used for storage and processing in programs. Data
How to create:
1, put the value in {} to create an empty dictionary;
2, use the method dict() to create an empty dictionary

data = {  
     "name" : "神行太保戴宗",  
     'title' :'天速星',  
     'age' : 45,  
     'price' : 490  
}

To access Dictionary members use the keyword index operator s[name]:

name = data['name'];  
title = data['title'];  
age = data['age'];  
print(name);  
print(title);  
print(age);

The output result is:

神行太保戴宗
天速星
45

Methods to insert or modify objects:

data['book'] = '水浒传之梁山108将'; #插入  
data['name'] = '插翅虎雷横';  #修改  
data['title'] = '天退星';

Output result:

水浒传之梁山108将
插翅虎雷横
天退星

String is a commonly used keyword type
Find unordered data:

prices = {  
 'apple' :3.4,  
 'banana' : 4,  
 'orange' : 2.5,  
 'lemon' : 3.7,  
  'pear' : 1.8  
}

applePrice = prices['apple'];

Output result:

3.4

How to determine whether an item is a member of the current dictionary:
1, use the in operator to test whether a content item is a member of the dictionary

if "grape" in prices:  
  p = prices['grape'];  
else:  
  p= 0;  
print(p);

Output result:

0

2, use the system method get to determine whether it is a dictionary member

p = prices.get('grape',0);  
  
print(p);

Output result:

0

Get the dictionary key The list of words only needs to convert the dictionary into a list:

pricelist = list(prices);

Output result:

['orange', 'lemon', 'pear', 'banana', 'apple']

Method to delete dictionary elements del:

del prices['pear'];

Output result:

{'apple': 3.4, 'banana': 4, 'lemon': 3.7, 'orange': 2.5}

Summary:
1. What is the dict dictionary? : is an associative array or hash table
2, create dictionary: 1, {} 2, dict()
2, purpose of dictionary: used to quickly find unordered data and often used to store and process data
3, use dictionary keyword index to obtain data
4, dictionary insertion and modification: use keyword index to add or modify the format s[name] = 'data';
5, determine whether the element exists in the dictionary : 1, in 2, get
6, method to get dictionary keywords: list is declared as list
6, deletes elements in the dictionary: del method

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