Python读写JSON配置文件的简明学习指南

目录

• 1. 基本读写操作
• 读取 JSON 配置文件
• 写入 JSON 配置文件
• 2. 简单配置管理器
• 3. 带环境变量支持的配置
• 4. 处理特殊数据类型的配置
• 5. 配置验证
• 快速使用总结

import json

# 创建示例配置文件
config_data = {
    "database": {
        "host": "localhost",
        "port": 3306,
        "username": "admin"
    },
    "settings": {
        "debug": True,
        "log_level": "INFO"
    }
}

with open("config.json", "w", encoding="utf-8") as f:
    json.dump(config_data, f, indent=2, ensure_ascii=False)

# 读取 JSON 文件
with open("config.json", "r", encoding="utf-8") as f:
    config = json.load(f)
    print("配置文件内容:")
    print(json.dumps(config, indent=2, ensure_ascii=False))
    
# 访问配置值
db_host = config["database"]["host"]
debug_mode = config["settings"]["debug"]
print(f"n数据库主机: {db_host}")
print(f"调试模式: {debug_mode}")

import json

# 创建配置数据
config = {
    "app": {
        "name": "我的应用",
        "version": "1.0.0"
    },
    "server": {
        "host": "0.0.0.0",
        "port": 8080
    }
}

# 写入到文件
with open("app_config.json", "w", encoding="utf-8") as f:
    json.dump(config, f, indent=4, ensure_ascii=False)

print("配置文件已保存到: app_config.json")

# 验证写入
with open("app_config.json", "r", encoding="utf-8") as f:
    loaded = json.load(f)
    print(f"应用名称: {loaded['app']['name']}")
    print(f"服务器端口: {loaded['server']['port']}")

import json
import os
from typing import Any, Dict

class SimpleConfig:
    def __init__(self, filename: str = "config.json"):
        self.filename = filename
        self.config = {}
    
    def load(self) -> Dict[str, Any]:
        """加载配置文件"""
        if os.path.exists(self.filename):
            with open(self.filename, "r", encoding="utf-8") as f:
                self.config = json.load(f)
        else:
            self.config = self.get_default_config()
            self.save()
        return self.config
    
    def save(self) -> None:
        """保存配置文件"""
        with open(self.filename, "w", encoding="utf-8") as f:
            json.dump(self.config, f, indent=2, ensure_ascii=False)
    
    def get_default_config(self) -> Dict[str, Any]:
        """获取默认配置"""
        return {
            "app": {
                "name": "默认应用",
                "version": "1.0.0"
            },
            "database": {
                "host": "localhost",
                "port": 5432
            }
        }
    
    def get(self, *keys) -> Any:
        """获取配置值"""
        value = self.config
        for key in keys:
            if isinstance(value, dict) and key in value:
                value = value[key]
            else:
                return None
        return value
    
    def set(self, *keys_and_value) -> None:
        """设置配置值
        参数格式: key1, key2, ..., value
        例如: set("database", "host", "192.168.1.100")
        """
        if len(keys_and_value) < 2:
            raise ValueError("至少需要2个参数: keys和value")
        
        *keys, value = keys_and_value
        
        # 遍历到倒数第二个键
        current = self.config
        for key in keys[:-1]:
            if key not in current or not isinstance(current[key], dict):
                current[key] = {}
            current = current[key]
        
        # 设置最后一个键的值
        current[keys[-1]] = value
        self.save()

# 使用示例
config = SimpleConfig("my_config.json")

# 加载配置
config.load()

# 获取配置
app_name = config.get("app", "name")
print(f"应用名称: {app_name}")

# 设置新配置
config.set("database", "host", "192.168.1.100")
config.set("app", "debug", True)
config.set("logging", "level", "DEBUG")

# 验证设置
print(f"数据库主机: {config.get('database', 'host')}")
print(f"调试模式: {config.get('app', 'debug')}")
print(f"日志级别: {config.get('logging', 'level')}")

# 查看完整的配置
print(f"n完整配置: {json.dumps(config.config, indent=2, ensure_ascii=False)}")

# 清理临时文件
if os.path.exists("my_config.json"):
    os.remove("my_config.json")

import json
import os
from typing import Any, Dict

class EnvConfig:
    def __init__(self, config_file: str = "config.json", env_prefix: str = "APP_"):
        self.config_file = config_file
        self.env_prefix = env_prefix
        self.config = {}
    
    def load(self) -> Dict[str, Any]:
        """加载配置，环境变量优先于文件配置"""
        # 1. 加载文件配置
        if os.path.exists(self.config_file):
            with open(self.config_file, "r", encoding="utf-8") as f:
                self.config = json.load(f)
        else:
            self.config = {}
        
        # 2. 用环境变量覆盖
        self._apply_env_vars()
        
        return self.config
    
    def _apply_env_vars(self) -> None:
        """应用环境变量到配置"""
        for env_key, env_value in os.environ.items():
            if env_key.startswith(self.env_prefix):
                # 转换环境变量名: APP_DATABASE_HOST -> database.host
                config_key = env_key[len(self.env_prefix):].lower()
                
                # 转换值类型
                value = self._convert_value(env_value)
                
                # 设置到配置中
                self._set_nested(config_key, value)
    
    def _convert_value(self, value: str) -> Any:
        """转换字符串值为适当类型"""
        # 布尔值
        if value.lower() in ("true", "false"):
            return value.lower() == "true"
        
        # 数字
        try:
            if "." in value:
                return float(value)
            return int(value)
        except ValueError:
            pass
        
        # 列表（逗号分隔）
        if "," in value:
            return [item.strip() for item in value.split(",")]
        
        return value
    
    def _set_nested(self, key_path: str, value: Any) -> None:
        """设置嵌套配置"""
        parts = key_path.split("_")
        current = self.config
        
        for part in parts[:-1]:
            if part not in current or not isinstance(current[part], dict):
                current[part] = {}
            current = current[part]
        
        current[parts[-1]] = value
    
    def save(self) -> None:
        """保存配置到文件"""
        with open(self.config_file, "w", encoding="utf-8") as f:
            json.dump(self.config, f, indent=2, ensure_ascii=False)

# 使用示例
# 设置环境变量
os.environ["APP_DATABASE_HOST"] = "prod-db.example.com"
os.environ["APP_DEBUG"] = "true"
os.environ["APP_LOG_LEVEL"] = "WARNING"

# 创建文件配置
file_config = {
    "database": {
        "host": "localhost",  # 将被环境变量覆盖
        "port": 3306
    },
    "app": {
        "debug": False,  # 将被环境变量覆盖
        "log_level": "INFO"  # 将被环境变量覆盖
    }
}

# 保存文件配置
with open("env_config.json", "w", encoding="utf-8") as f:
    json.dump(file_config, f, indent=2, ensure_ascii=False)

# 加载配置
config = EnvConfig("env_config.json")
config_data = config.load()

print("最终配置:")
print(json.dumps(config_data, indent=2, ensure_ascii=False))

# 清理
os.remove("env_config.json")
del os.environ["APP_DATABASE_HOST"]
del os.environ["APP_DEBUG"]
del os.environ["APP_LOG_LEVEL"]

import json
from datetime import datetime, date
from decimal import Decimal
from enum import Enum
from typing import Any

class CustomJSONEncoder(json.JSONEncoder):
    """自定义 JSON 编码器，支持更多数据类型"""
    
    def default(self, obj: Any) -> Any:
        if isinstance(obj, (datetime, date)):
            return obj.isoformat()
        elif isinstance(obj, Decimal):
            return float(obj)
        elif isinstance(obj, Enum):
            return obj.value
        elif hasattr(obj, '__dict__'):
            return obj.__dict__
        return super().default(obj)

# 定义数据类型
class LogLevel(Enum):
    DEBUG = "DEBUG"
    INFO = "INFO"
    WARNING = "WARNING"
    ERROR = "ERROR"

# 创建包含特殊类型的数据
config_data = {
    "app": {
        "name": "数据分析",
        "created": datetime.now(),
        "version": "2.0.0"
    },
    "database": {
        "host": "localhost",
        "port": 5432,
        "timeout": 30.5
    },
    "logging": {
        "level": LogLevel.INFO,
        "retention_days": Decimal("90.5")
    },
    "features": ["auth", "api", "dashboard"]
}

# 使用自定义编码器保存
with open("special_config.json", "w", encoding="utf-8") as f:
    json.dump(config_data, f, cls=CustomJSONEncoder, indent=2, ensure_ascii=False)

print("包含特殊类型的配置文件已保存")

# 读取和验证
with open("special_config.json", "r", encoding="utf-8") as f:
    loaded = json.load(f)
    print("n读取的配置:")
    print(f"应用名称: {loaded['app']['name']}")
    print(f"创建时间: {loaded['app']['created']}")
    print(f"日志级别: {loaded['logging']['level']}")
    print(f"保留天数: {loaded['logging']['retention_days']}")

# 清理
import os
os.remove("special_config.json")

import json
from typing import Any, Dict, List

class ConfigValidator:
    """简单的配置验证器"""
    
    def validate(self, config: Dict[str, Any], rules: Dict[str, Any]) -> List[str]:
        """验证配置"""
        errors = []
        
        for key, rule in rules.items():
            if key not in config:
                if rule.get("required", False):
                    errors.append(f"缺少必要字段: {key}")
                continue
            
            value = config[key]
            value_type = rule.get("type")
            
            # 检查类型
            if value_type and not isinstance(value, value_type):
                errors.append(f"{key} 应为 {value_type.__name__} 类型")
            
            # 检查枚举值
            if "enum" in rule and value not in rule["enum"]:
                errors.append(f"{key} 的值 {value} 不在允许范围内: {rule['enum']}")
            
            # 检查范围
            if "min" in rule and value < rule["min"]:
                errors.append(f"{key} 的值 {value} 小于最小值 {rule['min']}")
            
            if "max" in rule and value > rule["max"]:
                errors.append(f"{key} 的值 {value} 大于最大值 {rule['max']}")
        
        return errors

# 使用示例
config = {
    "app": {
        "name": "我的应用",
        "version": "1.0.0"
    },
    "database": {
        "host": "localhost",
        "port": 3306,
        "timeout": 30
    },
    "server": {
        "port": 8080,
        "workers": 4
    }
}

# 定义验证规则
validation_rules = {
    "app": {
        "type": dict,
        "required": True
    },
    "database": {
        "type": dict,
        "required": True
    },
    "server": {
        "type": dict,
        "required": True
    }
}

database_rules = {
    "host": {
        "type": str,
        "required": True
    },
    "port": {
        "type": int,
        "required": True,
        "min": 1,
        "max": 65535
    },
    "timeout": {
        "type": int,
        "required": True,
        "min": 1
    }
}

# 验证配置
validator = ConfigValidator()

# 验证顶层
errors = validator.validate(config, validation_rules)
if errors:
    print("配置验证失败:")
    for error in errors:
        print(f"  - {error}")
else:
    print("✓ 顶层配置验证通过")

# 验证数据库配置
db_errors = validator.validate(config["database"], database_rules)
if db_errors:
    print("数据库配置验证失败:")
    for error in db_errors:
        print(f"  - {error}")
else:
    print("✓ 数据库配置验证通过")

# 保存验证通过的配置
if not errors and not db_errors:
    with open("validated_config.json", "w", encoding="utf-8") as f:
        json.dump(config, f, indent=2, ensure_ascii=False)
    print("n✓ 配置已保存到: validated_config.json")
    
    # 清理
    import os
    os.remove("validated_config.json")

• 基本读写：使用 json.load() 和 json.dump()
• 中文支持：添加 ensure_ascii=False
• 格式美观：使用 indent 参数
• 错误处理：检查文件是否存在
• 类型转换：JSON 支持基本类型，复杂类型需要自定义处理

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