python学习笔记（八）—— json.dump()和json.load()

使用json.dump()和json.load()编码和解码JSON数据。

 

使用json.dump()存储一组数字，编码JSON数据

import json
numbers = [2,3,5,7,11,13]
filename = 'numbers.json'
with open(filename,'w') as f_obj:
    #使用json.dump()将数字列表存储到文件numbers.json中
    json.dump(numbers,f_obj)

使用json.load()将列表读取到内存中。解码JSON数据

import json
filename = 'numbers.json'
with open(filename) as f_obj:
    numbers = json.load(f_obj)
print(numbers)

保存和读取用户生成的数据例子：

import json
username = input("What is your name? ")
filename2 = 'username.json'
with open(filename2,'w') as f2_obj:
    json.dump(username,f2_obj)
    print("We will remember you when you come back, " + username + "!")

如果以前存储了用户名，就加载它；否则，就提示用户输入用户名并存储它：

import json
filename3 ='username3.json'
try:
    with open(filename3) as f3_obj:
        username3 = json.load(f3_obj)
except FileNotFoundError:
    username3 = input("What is your name? ")
    with open(filename3,'w') as f3_obj:
        json.dump(username3,f3_obj)
        print("We will remember you when you come back, " + username3 + "!")
else:
    print("Welcome back, " + username3 + "!")

重构上面的代码，使之更易于阅读：

import json
def get_stored_username():
    filename3 ='username3.json'
    try:
        with open(filename3) as f3_obj:
            username3 = json.load(f3_obj)
    except FileNotFoundError:    
        return None
    else:
        return username3
def get_new_username():
    username3 = input("What is your name? ")
    filename3 ='username3.json'
    with open(filename3,'w') as f3_obj:
        json.dump(username3,f3_obj)
    return(username3)
def greet_user():
    username3 = get_stored_username()
    if username3:
        print("Welcome back, " + username3 + "!")
    else:
        username3 = get_new_username()
        print("We will remember you when you come back, " + username3 + "!")
greet_user()