Python json.dump详解 - 文件写入与流式序列化技巧

import json

json.dump(obj, fp, *, skipkeys=False, ensure_ascii=True,
           check_circular=True, allow_nan=True,
           cls=None, indent=None, separators=None,
           default=None, sort_keys=False, **kw)

import json

data = {
    "users": [
        {"id": 1, "name": "张三", "role": "admin"},
        {"id": 2, "name": "李四", "role": "user"},
    ],
    "total": 2,
    "updated": "2024-01-15",
}

# 写入JSON文件
with open("users.json", "w", encoding="utf-8") as f:
    json.dump(data, f, ensure_ascii=False, indent=2)

print("已写入 users.json")

# 读取验证
with open("users.json", "r", encoding="utf-8") as f:
    content = f.read()
print(content)

已写入 users.json
{
  "users": [
    {
      "id": 1,
      "name": "张三",
      "role": "admin"
    },
    {
      "id": 2,
      "name": "李四",
      "role": "user"
    }
  ],
  "total": 2,
  "updated": "2024-01-15"
}

import json

def generate_large_data(count):
    """生成大量数据"""
    for i in range(count):
        yield {"id": i, "value": f"item_{i}", "score": i * 0.5}

# 方式1：一次性写入（占用内存大）
data_list = list(generate_large_data(5))
with open("data_batch.json", "w", encoding="utf-8") as f:
    json.dump(data_list, f, ensure_ascii=False, indent=2)
print("批量写入完成")

# 方式2：手动流式写入（节省内存）
with open("data_stream.json", "w", encoding="utf-8") as f:
    f.write("[\n")
    first = True
    for item in generate_large_data(5):
        if not first:
            f.write(",\n")
        json.dump(item, f, ensure_ascii=False, indent=2)
        first = False
    f.write("\n]")
print("流式写入完成")

批量写入完成
流式写入完成

import json
import os

class ConfigManager:
    """JSON配置文件管理器"""

    def __init__(self, filepath):
        self.filepath = filepath
        self.config = {}
        if os.path.exists(filepath):
            self.load()

    def load(self):
        """从文件加载配置"""
        with open(self.filepath, "r", encoding="utf-8") as f:
            self.config = json.load(f)

    def save(self):
        """保存配置到文件"""
        with open(self.filepath, "w", encoding="utf-8") as f:
            json.dump(self.config, f, ensure_ascii=False, indent=2)

    def get(self, key, default=None):
        return self.config.get(key, default)

    def set(self, key, value):
        self.config[key] = value
        self.save()

    def delete(self, key):
        if key in self.config:
            del self.config[key]
            self.save()

    def display(self):
        print(f"配置文件: {self.filepath}")
        for key, value in self.config.items():
            print(f"  {key}: {value}")

# 使用示例
config = ConfigManager("app_config.json")
config.set("app_name", "我的应用")
config.set("version", "1.0.0")
config.set("debug", True)
config.set("max_connections", 100)
config.display()

配置文件: app_config.json
  app_name: 我的应用
  version: 1.0.0
  debug: True
  max_connections: 100