Python學習筆記之json.dump和json.load

10-11 喜歡的數字：編寫一個程序，提示用戶輸入他喜歡的數字，並使用json.dump()將這個數字存儲到文件中。再編寫一個程序，從文件中讀取這個值，並打印消息“I know your favorite number! It’s _____.”。

favorite_number.py

import json

def favorite_number():
    """提示用戶輸入喜歡的數字"""
    filename = 'favorite_number.json'
    number = input("請輸入你喜歡的數字：")
    with open(filename, 'w') as f_obj:
        json.dump(number, f_obj)

favorite_number()

get_favorite_number.py

import json

def get_favorite_number():
    """獲取文件內容"""
    filename = 'favorite_number.json'
    with open(filename) as f_obj:
        get_number = json.load(f_obj)

    print("I know your favorite number! It’s " + str(get_number) + ".")

get_favorite_number()

 

10-12 記住喜歡的數字：將練習10-11 中的兩個程序合而為一。如果存儲了用戶喜歡的數字，就向用戶顯示它，否則提示用戶輸入他喜歡的數字並將其存儲到文件中。運行這個程序兩次，看看它是否像預期的那樣工作。

import json

def get_stored_number():
    filename = 'favorite_number.json'
    try:
        with open(filename) as f_obj:
            number = json.load(f_obj)
    except FileNotFoundError:
        return None
    else:
        return number

def favorite_number():
    """提示用戶輸入喜歡的數字"""
    filename = 'favorite_number.json'
    number = input("請輸入你喜歡的數字：")
    with open(filename, 'w') as f_obj:
        json.dump(number, f_obj)
    return number


def get_favorite_number():
    """獲取文件內容"""
    # filename = 'favorite_number.json'
    # with open(filename) as f_obj:
    #     get_number = json.load(f_obj)
    number = get_stored_number()
    if number:
        print("I know your favorite number! It’s " + str(number) + ".")
    else:
        number = favorite_number()
        print("I know your favorite number! It’s " + str(number) + ".")

get_favorite_number()

 

10-13 驗證用戶：最后一個remember_me.py 版本假設用戶要么已輸入其用戶名，要么是首次運行該程序。我們應修改這個程序，以應對這樣的情形：當前和最后一次運行該程序的用戶並非同一個人。

為此，在greet_user()中打印歡迎用戶回來的消息前，先詢問他用戶名是否是對的。如果不對，就調用get_new_username()讓用戶輸入正確的用戶名。

原remember_me.py代碼

import json

def get_stored_username():
    """如果存儲了用戶名，就獲取它"""
    filename = 'username.json'
    try:
        with open(filename) as f_obj:
            username = json.load(f_obj)
    except FileNotFoundError:
        return None
    else:
        return username

def get_new_username():
    """提示用戶輸入用戶名"""
    username = input("What is your name? ")
    filename = 'username.json'
    with open(filename, 'w') as f_obj:
        json.dump(username, f_obj)
    return username

def greet_user():
    """問候用戶，並指出其名字"""
    username = get_stored_username()
    if username:
        print("Welcome come back, " + username + "!")
    else:
        username = get_new_username()
        print("We will remember you when you come back, " + username + "!")

greet_user()

修改之后remember_me.py代碼

import json

def get_stored_username():
    """如果存儲了用戶名，就獲取它"""
    filename = 'username.json'
    try:
        with open(filename) as f_obj:
            username = json.load(f_obj)
    except FileNotFoundError:
        return None
    else:
        return username

def get_new_username():
    """提示用戶輸入用戶名"""
    username = input("What is your name? ")
    filename = 'username.json'
    with open(filename, 'w') as f_obj:
        json.dump(username, f_obj)
    return username

def greet_user():
    """問候用戶，並指出其名字"""
    username = get_stored_username()
    if username:
        msg = "Are you " + username + "? (y/n) " 27 correct = input(msg) 28 if correct == 'y': 29 print("Welcome come back, " + username + "!") 30 else: 31 username = get_new_username() 32 print("We will remember you when you come back, " + username + "!") 33 
    else:
        username = get_new_username()
        print("We will remember you when you come back, " + username + "!")

greet_user()