序列化
什么是序列化
序列化是将字典、列表等数据类型转化成一个字符串的过程
序列化的目的
1. 以某种存储形式使自定义对象持久化（存储）
2. 将对象从一个地方传递到另一个我地方（传输）
3. 使程序更具维护性
json模块
json是很多语言通用的一种数据标准，json可以转化的数据类型包括：str int bool dict list(tuple) None
json模块有四种方法：dumps， loads, dump, load
dumps和loads
处理列表
import
json
lst = [1, 2, "a", "哈哈"]
s = json.dumps(lst, ensure_ascii=False) # 包含非ascii字符时要加上ensure_ascii=Falseprint(s[0]) # [ 可以像字符串一样取值print(s[1]) # 1print(s[1:8]) # 也可以切片 1, 2, " 注意列表元素之间有空格print(s, type(s)) # [1, 2, "a", "哈哈"] <class ‘str‘>
l1 = json.loads(s)
print(l1, type(l1)) # [1, 2, ‘a‘, ‘哈哈‘] <class ‘list‘>
dumps也可以处理嵌套的数据类型，注意json会自动把字典的key变成字符串格式，元组转化之后会变成列表
1
import
json
2 dic = {"1": {1: "青", 2: "梅", 3: "竹", 4: "马"}, "2": {1: "两", 2: "小", 3: "无", 4: "猜"}}
3 s = json.dumps(dic, ensure_ascii=False)
4# print(s)5 dic1 = json.loads(s)
6print(dic1) # {‘1‘: {‘1‘: ‘青‘, ‘2‘: ‘梅‘, ‘3‘: ‘竹‘, ‘4‘: ‘马‘}, ‘2‘: {‘1‘: ‘两‘, ‘2‘: ‘小‘, ‘3‘: ‘无‘, ‘4‘: ‘猜‘}}
dump和load
dump和load用于将数据写入文件和读出
1
import
json
2 dic = {1: "你", 2: "我"}
3 with open("序列化.json", encoding="utf-8", mode="w") as f1:
4 json.dump(dic, f1, ensure_ascii=False)
56 with open("序列化.json", encoding="utf-8", mode="r") as f2:
7 ret = json.load(f2)
89print(ret) # {‘1‘: ‘你‘, ‘2‘: ‘我‘}
一次只能写入一个数据，超过一个读取就会出错
1
import
json
2 dic1 = {1: "你", 2: "我"}
3 dic2 = {1: "我", 2: "你"}
4 a = None
5 with open("序列化.json", encoding="utf-8", mode="w") as f1:
6 json.dump(dic1, f1, ensure_ascii=False)
7 json.dump(dic2, f1, ensure_ascii=False)
8 9 with open("序列化.json", encoding="utf-8", mode="r") as f2:
10 ret1 = json.load(f2) # 报错json.decoder.JSONDecodeError: Extra data: line 1 column 21 (char 20)
11 ret2 = json.load(f2)
怎么同时写入多个数据呢，循环使用dumps，先用dumps把数据转化成json字符串，再用文件句柄写入
1
import
json
2 dic1 = {1: "你", 2: "我"}
3 dic2 = {1: "我", 2: "你"}
4 a = None # 写进文件会变成null 5 b = 100
6 c = (1, 2, 3)
7 d = True
8 with open("序列化.json", encoding="utf-8", mode="w") as f1:
9 f1.write(json.dumps(dic1, ensure_ascii=False)) # {"1": "你", "2": "我"}10 f1.write("n")
11 f1.write(json.dumps(dic2, ensure_ascii=False)) # {"1": "我", "2": "你"}12 f1.write("n")
13 f1.write(json.dumps(a)) # null14 f1.write("n")
15 f1.write(json.dumps(b)) # 10016 f1.write("n")
17 f1.write(json.dumps(c)) # [1, 2, 3] # 元组反序列化之后是列表18 f1.write("n")
19 f1.write(json.dumps(d)) # true
pickle模块
json模块只能将常用的数据类型进行序列化，pickle模块是python独有的，可以将所有的python的数据类型（包括对象)序列化
1
import
pickle
2 dic1 = {1: "你", 2: "我"}
3 p1 = pickle.dumps(dic1)
4print(p1) # b‘x80x03}qx00(Kx01Xx03x00x00x00xe4xbdxa0qx01Kx02Xx03x00x00x00xe6x88x91qx02u.‘
pickle是将数据类型转化成bytes类型存入文件中，用load也可以读出来
with open("p1.pickle", mode="rb") as f2: # 注意这里是rb模式 re = pickle.load(f2) print(re) # {1: ‘你‘, 2: ‘我‘}
与json不同，pickle可以一次写入和读取多个数据
1
import
pickle
2 dic1 = {1: "你", 2: "我"}
3 dic2 = {1: "我", 2: "你"}
4 a = None # 写进文件会变成null 5 b = 100
6 c = (1, 2, 3)
7 d = True
8 with open("p1.pickle", mode="wb") as f1:
9 pickle.dump(dic1, f1)
10 pickle.dump(dic2, f1)
11 pickle.dump(a, f1)
12 pickle.dump(b, f1)
13 pickle.dump(c, f1)
1415 with open("p1.pickle", mode="rb") as f2:
16 ret1 = pickle.load(f2)
17 ret2 = pickle.load(f2)
18 ret3 = pickle.load(f2)
19 ret4 = pickle.load(f2)
20 ret5 = pickle.load(f2) # pickle反序列化出来还是元组21print(ret1) # {1: ‘你‘, 2: ‘我‘}22print(ret2) # {1: ‘我‘, 2: ‘你‘}23print(ret3) # None24print(ret4) # 10025print(ret5) # (1, 2, 3)
pickle也可以转化python对象
1
import
pickle
2
def
func():
3
print(111)
4 5 6 with open("p2.pickle", mode="wb") as f1: # 模式必须是wb 7 pickle.dump(func, f1)
8 910 with open("p2.pickle", mode="rb") as f2:
11 re = pickle.load(f2)
12print(re) # <function func at 0x000001D1FF081E18>
json与pickele比较
1. json是通用的，别的语言也可以识别，pickle只能python识别
2. json只能转化str int bool dict list(tuple) None，pickle可以转化所有Python数据类型
shelve模块
shelve也是python提供给我们的序列化工具，比pickle用起来更简单一些。shelve只提供给我们一个open方法，是用key来访问的，使用起来和字典类似
1
import
shelve
2 f = shelve.open("shelve_file") # 写入了三个文件bak dat dir3 f["key"] = {"int": 10, "float": 3.4}
4f.close()
56 f = shelve.open("shelve_file")
7print(f["key"]) # {‘int‘: 10, ‘float‘: 3.4}8 f.close()
存储到shelve的文件一般不让修改，如果要修改可以加一个参数writeback=True
不加参数
1 f1 = shelve.open("shelve_file")
2 f1["key"]["int"] = 20
3f1.close()
45 f2 = shelve.open("shelve_file")
6print(f2["key"]) # {‘int‘: 10, ‘float‘: 3.4} 并没有修改
加上writeback=True
1 f3 = shelve.open("shelve_file", writeback=True)
2 f3["key"]["int"] = 20
3f3.close()
45 f4 = shelve.open("shelve_file")
6print(f4["key"]) # {‘int‘: 20, ‘float‘: 3.4}7 f4.close()
总结
1. 序列化就是把其他数据类型转化成字符串的过程
2. 常用的序列化模块是json，可以不同语言间通用，使用方法有dumps, loads 和dump, load
3. pickle是python独有的，可以转化所有Python数据类型
4. shelve像字典一样可以用key来访问，一般不让修改
原文：https://www.cnblogs.com/zzliu/p/10246407.html
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