python 对象（字典）、json相互转化

1. 对象、json相互转化

1.1 json的api有下面4个：

json.loads() 将json转换为dict
json.dumps() 将dict转换为json
json.load() 将json文件转换为dict
json.dump() 将dict转换为json文件 person.json
注意：dict也可以是类对象

1.2 dict转换为json

import json

person = {
    
    
  'name': 'jack',
  'age': 15,
  'email': '[email protected]'
}

print('dict：', person)
person_json = json.dumps(person) # 转换为json
print('json：', person_json)


# 输出
# dict： {'name': 'jack', 'age': 15, 'email': '[email protected]'}
# json： {"name": "jack", "age": 15, "email": "[email protected]"}

1.3 json转换为dict

import json
person_dict = json.loads('{"name": "jack", "age": 15, "email": "[email protected]"}')
 
print('person dict:', person_dict)

# 输出
# person dict: {'name': 'jack', 'age': 15, 'email': '[email protected]'}

1.4 类对象转换为json

import json

class Person:

  def __init__(self, name, age, email):
    self.name = name
    self.age = age
    self.email = email

person = Person('tom', 38, '[email protected]')
person_json = json.dumps(person.__dict__)
print('person json:', person_json)

# 输出
# person json: {"name": "tom", "age": 38, "email": "[email protected]"}

json.dumps() 不能直接传递一个对象实例否则回报 TypeError: Object of type Person is not JSON serializable 错误 为了避免这个错误，我们需要修改：

import json
class Person:

  def __init__(self, name, age, email):
    self.name = name
    self.age = age
    self.email = email

# 将person转换为dict
def convert2json(person):
  return {
    
    
    'name': person.name,
    'age': person.age,
    'email': person.email
  }

person = Person('tom', 38, '[email protected]')
# 第二个参数传递转换函数，或者使用default=lambda o: o.__dict__
person_json = json.dumps(person, default=convert2json)
print('person json:', person_json)

1.5 json转换为类对象

import json

class Person:

  def __init__(self, name, age, email):
    self.name = name
    self.age = age
    self.email = email

def convert2json(dict_json):
  return Person(dict_json['name'], dict_json['age'], dict_json['email'])

person = json.loads('{"name": "tom", "age": 38, "email": "[email protected]"}', object_hook=convert2json)
print('person:', person)

# 输出
# person: <__main__.Person object at 0x10a7230b8>

1.6 dict/对象转换为json文件

import 
person = {
    
    "name": "tom", "age": 38, "email": "[email protected]"}

with open('person.json', 'w') as f:
	json.dump(person, f)

# 当前目录下会多一个person.json文件，内容是:
{
    
    "name": "tom", "age": 38, "email": "[email protected]"}

1.7 将json文件转换为dict/对象

import json
with open('person.json', 'r') as f:
	print(json.load(f))

# 输出
{
    
    'name': 'tom', 'age': 38, 'email': '[email protected]'}

2. python对象到json字符串的转换规则：

Python	JSON
dict	object
list, tuple	array
str, unicode	string
int, long, float	number
True	true
False	false
None	null

3. json字符串到python对象的转换规则：

JSON	Python
object	dict
array	list
string	unicode
number (int)	int, long
number (real)	float
false	False
null	None