Python教程：安全高效地从嵌套JSON数据中提取特定字段（如URL）

import requests
import json

class CharacterFetcher:
    def __init__(self, character_id):
        self.character_id = character_id
        self.character_data = self.get_character_data()

    def get_character_data(self):
        """
        从API获取角色数据并解析为Python字典。
        """
        req = requests.get(f"https://character-service.dndbeyond.com/character/v5/character/{self.character_id}")
        if req.status_code != 200:
            print(f"API请求失败，状态码: {req.status_code}")
            return None
        try:
            j = req.json() # 将JSON响应解析为Python字典
            if not "success" in j or not "data" in j:
                print("API响应结构不符合预期，缺少'success'或'data'键。")
                return None
            return j["data"] # 返回包含角色数据的核心字典

        except json.JSONDecodeError:
            print("无法解析API响应为JSON格式。")
            return None
        except requests.exceptions.RequestException as e:
            print(f"请求发生错误: {e}")
            return None

# 假设我们有一个character_data字典，其结构大致如下：
# character_data = {
#     'id': 108291017,
#     'userId': 118256620,
#     'username': 'sethirya',
#     'decorations': {
#         'avatarUrl': 'https://www.dndbeyond.com/avatars/21222/111/637708177497566513.jpeg?width=150&height=150&fit=crop&quality=95&auto=webp',
#         'frameAvatarUrl': '...'
#     },
#     'name': 'Raine',
#     # ... 其他字段
# }

# 假设 self.character_data 已经成功获取
# avatar_url = self.character_data["decorations"]["avatarUrl"]

class CharacterFetcher:
    # ... (前面的 __init__ 和 get_character_data 方法不变)

    def get_avatar_url(self):
        """
        安全地从角色数据中提取头像URL。
        """
        if not self.character_data:
            return "" # 如果角色数据本身就为空，直接返回空字符串

        # 使用链式 .get() 方法安全地访问嵌套键
        avatar_url = self.character_data.get("decorations", {}).get("avatarUrl", "")
        return avatar_url

# 示例使用
if __name__ == "__main__":
    character_id_example = 108291017 # 替换为实际的角色ID
    fetcher = CharacterFetcher(character_id_example)

    if fetcher.character_data:
        print(f"角色ID: {fetcher.character_data.get('id', 'N/A')}")
        print(f"角色名称: {fetcher.character_data.get('name', 'N/A')}")

        avatar_url = fetcher.get_avatar_url()
        if avatar_url:
            print(f"头像URL: {avatar_url}")
            # 此时你可以使用 requests.get(avatar_url) 来下载图片
            # 例如:
            # try:
            #     image_response = requests.get(avatar_url)
            #     if image_response.status_code == 200:
            #         with open("avatar.jpeg", "wb") as f:
            #             f.write(image_response.content)
            #         print("头像图片已下载到 avatar.jpeg")
            # except requests.exceptions.RequestException as e:
            #     print(f"下载头像图片失败: {e}")
        else:
            print("未找到头像URL或数据结构不匹配。")
    else:
        print("未能获取角色数据。")