使用Python 3写入JSON文件仅存最新条目，如何存储全部数据？

你的程序中logged_times字典仅保留最新8条条目，核心原因是每次启动程序时，number变量都从0开始初始化，而非从已存储的最大条目编号开始。这导致新记录会覆盖原有字典中相同数字键的旧记录，最终看起来只保留了最新的8条（当你重启程序8次后，旧的1-8键会被新的1-8覆盖）。

修复步骤 #

1. 正确初始化number变量 #

程序启动时，读取已有的日志条目，获取最大的编号值作为number的初始值，避免覆盖旧记录：

替换原来的number = 0为以下代码：

# 从已存储的日志中获取最大编号，初始化number
if logged_times:
    # JSON加载后键是字符串，需转为整数取最大值
    number = max(map(int, logged_times.keys()))
else:
    number = 0

2. 清理冗余代码 #

log函数中的logged_times和days两行是无效的冗余代码，可以直接删除。

修复后的完整代码 #

import json
from datetime import date

# 读取持久化数据，处理文件不存在的情况
try:
    with open("social_media_log.json", "r") as read_file:
        logged_times = json.load(read_file)
except FileNotFoundError:
    logged_times = {}

try:
    with open("social_media_log_DAYS.json", "r") as read_file:
        days = json.load(read_file)
except FileNotFoundError:
    days = []

today = date.today()
print(today)

# 初始化number为已有的最大条目编号
if logged_times:
    number = max(map(int, logged_times.keys()))
else:
    number = 0

def ask():
    print("What would you like to do?")
    print("L = LOG social media time")
    print("R = get a REPORT of usage")
    print("E = EXIT program")

    response = input().lower()
    
    if response == "l":
        log()
    elif response == "r":
        report()
    elif response == "e":
        return
    else:
        ask() 

def log():
    global number
    number += 1
    print("how long did you use social media just now? # of seconds")
    entry = input() 
    logged_times[str(number)] = {"date" : str(today), "amount" : entry}
    if str(today) not in days:
        days.append(str(today))
    
    # 计算并打印总时长
    amounts = [int(item['amount']) for item in logged_times.values()]
    print(f"total time is {sum(amounts)}")
    
    # 写入持久化文件
    with open("social_media_log.json", "w") as write_file:
        json.dump(logged_times, write_file)
    with open("social_media_log_DAYS.json", "w") as write_file:
        json.dump(days, write_file) 
    ask()

def report():
    # 可补充实现按日期统计等报表功能
    print("Report feature to be implemented.")
    ask()

# 启动程序
ask()

额外优化点 #

• 增加文件不存在时的异常处理，避免首次运行报错
• 将输入命令转为小写，支持大小写不敏感操作
• 用列表推导式简化总时长计算逻辑
• 将number转为字符串作为字典键，符合JSON键类型规范（JSON仅支持字符串键）

内容的提问来源于stack exchange，提问作者Sam J. Miller