python json模块小技巧

python的json模块通常用于与序列化数据，如

def get_user_info(user_id):
	res = {"user_id": 190013234,"nick": "havana"}
	json_str = json.dumps(res)
    return json_str

但是当要序列化的数据里面包含中文字符时，会变成这样

import json
res = {"user_id": 190027134, "nick": "愚蠢的萝卜"}
print(json.dumps(res))

# {"nick": "\u611a\u8822\u7684\u841d\u535c", "user_id": 190027134}

解决办法: 在json.dumps()里面加入一个参数ensure_ascii=False

import json
res = {"user_id": 190027134, "nick": "愚蠢的萝卜"}
print(json.dumps(res))

# {"nick": "愚蠢的萝卜", "user_id": 190027134}

这里有一个问题，如果json的结构很复杂，输出的结果就会很乱，不清晰，这是可以加入一个参数使其格式化

import json
res = {"user_id": 190027134, "nick": "愚蠢的萝卜"}
print(json.dumps(res))

# {
    "nick": "愚蠢的萝卜", 
    "user_id": 190027134
}

如果序列化的数据里面有python的datetime.datetime类型，那么序列化会报错

import datetime

res = {"user_id": 190027134, "nick": "愚蠢的萝卜", "reg_ts": datetime.datetime.now()}
print(json.dumps(res, ensure_ascii=False, indent=4))

#TypeError: datetime.datetime(2019, 11, 3, 19, 8, 45, 987000) is not JSON serializable

解决办法是使用自定义的jsonencoder代替原生的jsonencoder

class DatetimeEncoder(json.JSONEncoder):

    def default(self, obj):
        if isinstance(obj, datetime.datetime):
            return obj.strftime('%Y-%m-%d %H:%M:%S')
        elif isinstance(obj, datetime.date):
            return obj.strftime('%Y-%m-%d')
        else:
            return json.JSONEncoder.default(self, obj)


res = {"user_id": 190027134, "nick": "愚蠢的萝卜", "reg_ts": datetime.datetime.now(), "last_login_date": datetime.date.today()}
print(json.dumps(res, ensure_ascii=False, indent=4, cls=DatetimeEncoder))

# {
    "nick": "愚蠢的萝卜", 
    "user_id": 190027134, 
    "reg_ts": "2019-11-03 20:09:55", 
    "last_login_date": "2019-11-03"
}