如何在Python中处理API响应中缺失的JSON嵌套键？

问题场景 #

API返回的JSON响应中，部分字段可能为None，例如：

{  
    "associates": [
        {
            "name":"DOE",
            "fname":"John",
            "direct_shares":50,
            "direct_shares_details":{
               "shares_PP":25,
               "shares_NP":25
            },
            "indirect_shares":None,
            "indirect_shares_details": None
        } 
    ]
}

当尝试访问indirect_shares_details下的嵌套键（如first_type）时，会因该字段为None触发报错。现有处理函数存在此问题：

def get_shares_data(response):
    associate_from_api = []
    for i in response["associates"]:
        associate_data = {
        "PM_shares":  round(company["Shares"], 2),
        "full_name": i["name"] + " " + i["fname"],
        "details": {
                "shares_in_PM":    i["direct_shares"],
                "shares_PP_in_PM": i["direct_shares_details"]["shares_PP"],
                "shares_NP_in_PM": i["direct_shares_details"]["shares_NP"],
                "shares_directe":  i["indirect_shares"],
                "shares_indir_PP_1": i["indirect_shares_details"]["first_type"]["shares_PP"],
                "shares_indir_NP_1": i["indirect_shares_details"]["first_type"]["shares_NP"],
                "shares_indir_PP_2": i["indirect_shares_details"]["second_type"]["shares_PP"],
                "shares_indir_NP_2": i["indirect_shares_details"]["second_type"]["shares_NP"],
            }
        }
        for key,value in associate_data["details"].items():
            if value != None:
                associate_data["details"][key] = value * associate_data["PM_shares"] / 100
            else:
                associate_data["calculs"][key] = 0.0
        associate_from_api.append(associate_data)
    return associate_from_api

高效解决方法 #

方法1：使用字典get()方法链式调用 #

利用字典的get()方法，为每一层嵌套设置默认值，避免直接访问报错。若某一层为None，则返回预设的空字典，再继续处理：

def get_shares_data(response):
    associate_from_api = []
    pm_shares = round(company["Shares"], 2)
    for i in response["associates"]:
        # 安全获取间接持股详情，若为None则返回空字典
        indirect_details = i.get("indirect_shares_details", {}) or {}
        first_type = indirect_details.get("first_type", {}) or {}
        second_type = indirect_details.get("second_type", {}) or {}
        
        associate_data = {
            "PM_shares": pm_shares,
            "full_name": f"{i['name']} {i['fname']}",
            "details": {
                "shares_in_PM": i["direct_shares"],
                "shares_PP_in_PM": i["direct_shares_details"]["shares_PP"],
                "shares_NP_in_PM": i["direct_shares_details"]["shares_NP"],
                "shares_directe": i.get("indirect_shares"),
                "shares_indir_PP_1": first_type.get("shares_PP"),
                "shares_indir_NP_1": first_type.get("shares_NP"),
                "shares_indir_PP_2": second_type.get("shares_PP"),
                "shares_indir_NP_2": second_type.get("shares_NP"),
            }
        }
        # 统一处理数值计算，修正原函数未定义的calculs字段问题
        for key, value in associate_data["details"].items():
            if value is not None:
                associate_data["details"][key] = round(value * pm_shares / 100, 2)
            else:
                associate_data["details"][key] = 0.0
        associate_from_api.append(associate_data)
    return associate_from_api

方法2：编写通用安全取值函数 #

如果嵌套层级较多，可编写一个通用函数来安全获取多层嵌套的值，简化代码：

def safe_get(data, keys, default=None):
    """安全获取多层嵌套字典的值"""
    for key in keys:
        if data is None or not isinstance(data, dict):
            return default
        data = data.get(key, default)
    return data

def get_shares_data(response):
    associate_from_api = []
    pm_shares = round(company["Shares"], 2)
    for i in response["associates"]:
        associate_data = {
            "PM_shares": pm_shares,
            "full_name": f"{i['name']} {i['fname']}",
            "details": {
                "shares_in_PM": i["direct_shares"],
                "shares_PP_in_PM": i["direct_shares_details"]["shares_PP"],
                "shares_NP_in_PM": i["direct_shares_details"]["shares_NP"],
                "shares_directe": i.get("indirect_shares"),
                "shares_indir_PP_1": safe_get(i, ["indirect_shares_details", "first_type", "shares_PP"]),
                "shares_indir_NP_1": safe_get(i, ["indirect_shares_details", "first_type", "shares_NP"]),
                "shares_indir_PP_2": safe_get(i, ["indirect_shares_details", "second_type", "shares_PP"]),
                "shares_indir_NP_2": safe_get(i, ["indirect_shares_details", "second_type", "shares_NP"]),
            }
        }
        for key, value in associate_data["details"].items():
            if value is not None:
                associate_data["details"][key] = round(value * pm_shares / 100, 2)
            else:
                associate_data["details"][key] = 0.0
        associate_from_api.append(associate_data)
    return associate_from_api

关键修正点 #

• 处理indirect_shares_details为None的情况，通过get()或安全函数返回默认值，避免直接访问嵌套键报错
• 修正原函数中associate_data["calculs"]未定义的错误，统一将计算后的值写入details字典
• 使用f-string优化全名拼接，代码更简洁
• 增加round()保留小数位数，保证数值精度

内容的提问来源于stack exchange，提问作者user16779293