info = {
  "name":"tj",
  "age":22
}
import json
print(info)
print(type(info))
print(json.dumps(info))
print(type(json.dumps(info)))

f = open("test.txt","w")
# f.write(info)  # TypeError: write() argument must be str, not dict
f.write(json.dumps(info)) # 正常写入文件 f.write(json.dumps(info)) 等价于 json.dump(info, f)
f.close()

>
{'name': 'tj', 'age': 22}
<class 'dict'>
{"name": "tj", "age": 22}
<class 'str'>

f = open("test.txt","r")
# print(f.read()["age"]) #TypeError: string indices must be integers
data = json.loads(f.read()) # data = json.loads(f.read()) 等价于 data = json.load(f)
print(data["age"])
f.close()

>
22

import json
def hello(name):
  print("hello,",name)
info = {
  "name":"tj",
  "age":22,
  "func":hello
}
f = open("test2.txt","w")
f.write(json.dumps(info)) #TypeError: Object of type function is not JSON serializable
f.close()

import pickle
def hello(name):
  print("hello,",name)
info = {
  "name":"tj",
  "age":22,
  "func":hello
}

print(pickle.dumps(info)) #可见pickle序列化的结果输出为二进制，所以应使用wb的方式往文件中写
f = open("test2.txt","wb")
f.write(pickle.dumps(info)) # 等价于 pickle.dump(info,f)
f.close()

>
b'\x80\x04\x957\x00\x00\x00\x00\x00\x00\x00}\x94(\x8c\x04name\x94\x8c\x04alex\x94\x8c\x03age\x94K\x16\x8c\x04func\x94\x8c\x08__main__\x94\x8c\x05hello\x94\x93\x94u.'

f = open("test2.txt","rb")
data = pickle.loads(f.read()) # 等价于data = pickle.load(f)
print(data)
print(data["name"])
print(data["func"])

>
{'name': 'tj', 'age': 22, 'func': <function hello at 0x00000179EF69C040>}
tj
<function hello at 0x00000179EF69C040>

import json
info = {
  "name":"tj",
  "age":22
}

f = open("test3.txt","w")
f.write(json.dumps(info))
info['age'] = 21
f.write(json.dumps(info))
f.close()
# 
>
序列化两次后test3中的内容
test3.txt: {"name": "tj", "age": 22}{"name": "tj", "age": 21}

f = open("test3.txt","r")
# 报错，py3以上，多次dumps的文件反序列化报错，py2多次dumps的文件也能被反序列化，先序列化的先被反序列化
data = json.loads(f.read()) # json.decoder.JSONDecodeError
f.close()
print(data)

import pickle

info = {
  "name":"tj",
  "age":22
}

f = open("test2.txt","wb")
f.write(pickle.dumps(info)) # 等价于 pickle.dump(info,f)
info["sex"] = "女"
f.write(pickle.dumps(info)) # 等价于 pickle.dump(info,f)
f.close()

>
序列化两次后test2.txt中的内容
test2.txt： "test2.txt","rb")
data = pickle.loads(f.read()) # 第一次反序列化正常
# data = pickle.loads(f.read()) # 第二次反序列化：EOFError: Ran out of input
print(data)
print(data["age"])
# print(data["sex"]) # KeyError: 'sex'