python学习Day06--编码

【主要内容】

1. is 和 == 区别
      id()函数
      == 判断两边的值
      is 判断内存地址
回顾编码:
    1. ASCII: 英文, 特殊字符, 数字, 8bit, 1byte
    2. GBK: 中文 16bit, 2byte. 兼容ASCII
    3. unicode:　万国码, 32bit 4byte. 兼容ASCII
    4. UTF-8: 长度可变的unicode. 英文:8bit, 欧洲:１６bit, 中文:24bit 3byte

    python2 只能用ASCII
    python3 有unicode, 默认的编码就是unicode
    内存里用的是unicode. 硬盘和网络传输用的是utf-8或者GBK

2. encode()  编码. 获取到的是编码之后的结果. bytes
3. decode()  解码. 把bytes编程我们熟悉的字符串

【代码】

1、is和==

 # s = "alex 是 大 xx"
 # abc = id(s)   # 得到内存地址
 # print(abc)

 # lst = ["大阳哥", "佳琪哥", "小花生", "燃哥"]
 # print(id(lst))  # 就是一个内存地址. 毫无意义

 # lst = ["周杰伦", "燃哥"]
 # lst1 = ["周杰伦", "燃哥"]
 # print(id(lst))
 # print(id(lst1))

 # s = "燃哥"
 # s1 = "燃哥"
 # # 小数据池. 会对字符串进行缓存, 为了节省内存
 # print(id(s))
 # print(id(s1))

 # tu = ("燃哥", "周杰伦")
 # tu1 = ("燃哥", "周杰伦")
 # print(id(tu), id(tu1))

 # dic = {"a": "b", "c":"d"}
 # dic1 = {"a": "b", "c":"d"}
 # print(id(dic), id(dic1))

 # a = 10
 # b = 10
 # print(id(a), id(b))

 # 布尔也有,
 # a = True
 # b = True
 # print(id(a), id(b))

 # -5
 # a = 257
 # b = 257
 # print(id(a), id(b))

 # a = "小威"
 # b = "小威"
 # print(id(a), id(b))

 # 1. id() 查看内存地址
 # 2. str 有小数据池的

 # == is id
 # == 判断. 左右两端是否相等和一致, 比较的是内容
 # is 判断. 判断的是内存地址  id()的值来判断    内存地址

 # lst = ["马化腾", "小威"]
 # lst2 = ["马化腾", "小威"]
 # print(lst == lst2)  # True
 # print(lst is lst2)  # False

 # s = "alex"
 # print("1111111111")
 # print("1111111111")
 # print("1111111111")
 # print("1111111111")
 # print("1111111111")
 # print("1111111111")
 # print("1111111111")
 # print("1111111111")
 # print("1111111111")
 #
 # s2 = "alex"
 # print(s == s2) # True
 # print(s is s2)  # True. 小数据池

 # s1 = "@akljflkasdjklfjkasdlfjklsdajfklsdajfklasdjkflasdjklfjsdaklfjsdakljfklasdjfklsdajfklsdajfklsdajklfsjadklfjsadklfjasdkljfklsdjfklsdjfklsdjfklsdjfklasdjfklasdjklfjasdklakljflkasdjklfjkasdlfjklsdajfklsdajfklasdjkflasdjklfjsdaklfjsdakljfklasdjfklsdajfklsdajfklsdajklfsjadklfjsadklfjasdkljfklsdjfklsdjfklsdjfklsdjfklasdjfklasdjklfjasdkl"
 # s2 = "@akljflkasdjklfjkasdlfjklsdajfklsdajfklasdjkflasdjklfjsdaklfjsdakljfklasdjfklsdajfklsdajfklsdajklfsjadklfjsadklfjasdkljfklsdjfklsdjfklsdjfklsdjfklasdjfklasdjklfjasdklakljflkasdjklfjkasdlfjklsdajfklsdajfklasdjkflasdjklfjsdaklfjsdakljfklasdjfklsdajfklsdajfklsdajklfsjadklfjsadklfjasdkljfklsdjfklsdjfklsdjfklsdjfklasdjfklasdjklfjasdkl"
 # print(id(s1), id(s2))
 #
 # s = "abc中def"
 # print(s.title())

2、编码

 # s = "alex马"
 # 想要存储.必须进行编码

 # encode() 编码之后的内容是bytes类型的数据

 # 30个字节 10个字. 每个字3个字节
 # b'\xe6\x9d\x8e\xe5\x98\x89\xe8\xaf\x9a\xe7\x9a\x84\xe5\x84\xbf\xe5\xad\x90\xe8\xa2\xab\xe7\xbb\x91\xe6\x9e\xb6\xe4\xba\x86'
 # bs = s.encode("UTF-8")   # 把字符串编码成UTF-8的形式
 # print(bs)

 # 英文:编码之后的结果是英文本身
 # 中文:编码之后UTF-8 下. 一个中文3个字节

 # s = "饿了么"
 # bs = s.encode("GBK")    # b'\xb6\xf6\xc1\xcb\xc3\xb4' GBK 一个中文:２个字节
 # print(bs)

 # s = "中"
 # print(s.encode("utf-8"))
 # print(s.encode("GBK"))

 # decode()解码

 # bs = b'\xb6\xf6\xc1\xcb\xc3\xb4'    # 从别人那里读到的   GBK
 #
 # # 编程人认识的东西
 # s = bs.decode("GBK")    # 解码之后是字符串, 用什么编码就用什么解码
 # print(s)

 # GBK => utf-8
 bs = b'\xb6\xf6\xc1\xcb\xc3\xb4'
 # 先解码成unicode字符串
 s = bs.decode("GBK")
 # 在把字符串编码成UTF-8
 bss = s.encode("UTF-8")
 print(bss)

3、作业与练习

 '''

 s = "k:1|k1:2|k2:3|k3:4"
 lst=s.split("|")
 dic={}
 for i in lst:
     k,v = i.split(":")
     dic[k]=int(v)
 print(dic)

 # 有如下值li=[11,22,33,44,55,66,77,88,99,90]
 # 将所有大于66的值保存至字典的第一个key中，将小于66的所有值保存到第二个key值中
 li=[11,22,33,44,55,66,77,88,99,90]
 #法一
 # dic={"k1":[],"k2":[]}
 # for el in li:
 #     if el > 66:
 #         dic["k1"].append(el)
 #     elif el < 66:
 #         dic["k2"].append(el)
 #     else:
 #         pass
 # print(dic)
 dic={}
 for el in li:
     if el > 66:
         dic.setdefault("k1",[]).append(el)
     elif el < 66:
         dic.setdefault("k2",[]).append(el)
 print(dic)
 '''