python02-数据类型

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身份验证

• is；type(name) is int

  返回值为true或false、

• is not； type(name) is not int

  返回值为true或false

三元运算

• d = a if a > 15 else b
  d = 值1 if 条件A else值2
  
  如果条件A成立，就取左边的值1,否则取值2
  

数据类型-列表

• extend 合并

  n1 = ["bob","as","sdf"]
  name = ["张三","李四","王二"]
  
  name.extend(n1)
  print(name)
  
  
  ['张三', '李四', '王二', 'bob', 'as', 'sdf']
  

• 列表嵌套

  n1 = ["bob","as","sdf"]
  name = ["张三","李四","王二"]
  
  name.insert(1,n1)
  print(name)
  
  ['张三', ['bob', 'as', 'sdf'], '李四', '王二']
  

  n1 = ["bob","as","sdf"]
  name = ["张三","李四","王二"]
  
  name.insert(1,n1)
  print(name)
  print(name[1][1])
  
  
  ['张三', ['bob', 'as', 'sdf'], '李四', '王二']
  as
  

• 删除操作

  • del删

    name = ["张三","李四","王二","bob","as","sdf"]
    del name[1]
    print(name)
    
    
    ['张三', '王二', 'bob', 'as', 'sdf']
    

  • pop删

    name = ["张三","李四","王二","bob","as","sdf"]
    print(name.pop())
    print(name.pop(1))
    
    sdf
    李四
    

  • clear清空

    name = ["张三","李四","王二","bob","as","sdf"]
    print(name.clear())
    
    
    None
    

• 修改操作

  name = ["张三","李四","王二","bob","as","sdf"]
  name[0]="123"
  print(name)
  
  ['123', '李四', '王二', 'bob', 'as', 'sdf']
  

• 查操作

  name = ["张三","李四","王二","bob","as","sdf"]
  print(name.index("bob"))#返回从左开始匹配到的第一个eva的索引
  print(name.count("bob"))#返回eva的个数
  
  3
  1
  

• 切片 #原列表没有变化

  • 切片的特性是顾头不顾尾，即start的元素会被包含，end-1是实际取出来的值

  name = ["张三","李四","王二","bob","as","sdf"]
  print(name[1:4])
  print(name[1:-1])
  print(name[1:])  #:后面不写 就是取到最后
  print(name[:3])  #:前面不写 就是从头取
             
  ['李四', '王二', 'bob']
  ['李四', '王二', 'bob', 'as']
  ['李四', '王二', 'bob', 'as', 'sdf']
  ['张三', '李四', '王二']
  

  • 倒着切。倒着切也是从左往右切

  name = ["张三","李四","王二","bob","as","sdf"]
  print(name[-5:-1])
  
  ['李四', '王二', 'bob', 'as']
  

  • 步长

  name = ["张三","李四","王二","bob","as","sdf"]
  print(name[0:-1:2]) #头：尾：步长
  
  ['张三', '王二', 'as']
  

  • 真正的倒着切：从右往左切。需要把步长设为负数。

  name = ["张三","李四","王二","bob","as","sdf"]
  print(name[-1:-5])
  print(name[-1:-5:-1])  #倒着切
  
  []
  ['sdf', 'as', 'bob', '王二']  
  

  • 全切

  name = ["张三","李四","王二","bob","as","sdf"]
  print(name[::2])
  
  ['张三', '李四', '王二', 'bob', 'as', 'sdf']
  

• 反转

  • 切边：name[::-1]

  • .reverse #把原来的列表进行反转

    name = ["张三","李四","王二","bob","as","sdf"]
    name.reverse()
    print(name) #原列表发生了改变
    
    ['sdf', 'as', 'bob', '王二', '李四', '张三']
    

    • 字符串反转：

      n = '银角大王'
      print(n[::-1])
      
      王大角银
      

• 排序

  • .sort() #对原列表进行改变

  number = [12,32,123,432,1,3,5543,123]
  number.sort()
  print(number)
  
  [1, 3, 12, 32, 123, 123, 432, 5543]
  

  number = ['12','32','123','432','1','3','5543','123',"张三","李四","王二","bob","as","sdf"]
  number.sort()  #对ASCII值进行排序
  print(number)
  
  ['1', '12', '123', '123', '3', '32', '432', '5543', 'as', 'bob', 'sdf', '张三', '李四', '王二']
  
  

• 循环

  • for循环

  name = ["张三","李四","王二","bob","as","sdf"]
  for i in name:
      print(i)
      
  张三
  李四
  王二
  bob
  as
  sdf
  

数据类型-元组

• 元组不可修改-只读列表

name = ("apple","bob")
print(name[1])

bob

• 元组中有列表，可以更改列表的值；

  为啥呢？因为元组只是存每个元素的内存地址，上面['金角大王'，'Jack' ]这个列表本身的内存地址存在元组里确实不可变，但是这个列表包含的元素的内存地址是存在另外一块空间里的，是可变的。

name = ("apple","bob",["张三","李四"])
name[2][0]="王五"
print(name)

('apple', 'bob', ['王五', '李四'])

• 元组本身不可修改，如果包含可修改的数据类型，那么被包含的数据类型可以被修改。

数据类型-字符串

• 字符串是一个有序的字符的集合，用于存储和表示基本的文本信息，‘或”“或”"中间包含的内容称之为字符串

s = "Hello,Eva! How are you?"
print(s[1])

e

• 按照从左到右的顺序定义字符集合，下标从0开始顺序访问，有序。
• 可以进行切片操作。

s = "Hello,Eva! How are you?"
print(s[::3])

HlE!oa u

• 不可变，字符串是不可变的，不能像列表一样修改其中某个元素，所有对字符串的修改操作其实都是相当于生成了一份新数
  据。
• 字符串的单引号和双引号都无法取消特殊字符的含义，如果想让引号内所有字符均取消特殊意义，在引号前面加r(原生字符)。

name = "jack\t\n"
print(name)
print("=========")
name1 = r"jack\t\n"
print(name1)


jack	

=========
jack\t\n

• center() 填充

name  = "GuanSuo"
print(name.center(20, '-'))


------GuanSuo-------

• count() 计算

name  = "GuanSuoasbbb"
print(name.count("a"))
print(name.count("a", 1, 4))


2
1

• find() 找

name  = "GuanSuoasbbb"
print(name.find("a"))
print(name.find("a", 2)) #从2开始找

2
2

• format()

#两种方法实现
s = "My name is %s  , i am %s years old" %("alex",23) #1
print(s)

s1 = "My name is {0}  , i am {1} years old"  #2
print(s1.format("gs", 22))

s2 = "Welcome {name} to Apeland , you are No.{user_num} user."
print(s2.format(user_num=24, name="张三"))



My name is alex  , i am 23 years old
My name is gs  , i am 22 years old
Welcome 张三 to Apeland , you are No.24 user.

• join 拼接

name = ["shangsan","lisi","Wanger"]
print("? ".join(name))

shangsan? lisi? Wanger

• lower() #大写变成小些

name1 = "ASDasd"
print(name1.lower())

asdasd

• ljust() rjust()

str.ljust(width[, fillchar])

width -- 指定字符串长度。
fillchar -- 填充字符，默认为空格。

str = "this is string example....wow!!!"
print(str.ljust(50, '0'))

this is string example....wow!!!000000000000000000
000000000000000000this is string example....wow!!!

• strip() 删除首尾空白字符
  • rstrup() 删除右边空白字符
  • lstrup（）删除左边空白字符

str1 = "   Welcome to Guru99!    "
after_strip = str1.strip()
print(after_strip)


Welcome to Guru99!

• replace() 替换 默认所有的都改

a = "My score is 580, not 580 very good."
print(a.replace("580", "666"))
print(a.replace("580", "666"，1))     # 改一次
My score is 580, not 580 very good.
My score is 666, not 580 very good.

• split（）split():就是将一个字符串分隔成多个字符串组成的列表
  • 默认用空格分开
  • string.split("sep",num) num为分隔次数，有sep时按sep的值分隔:
  • rsplit（）从右开始。lsplit（）从左开始

a = "aaaaa bbbbb."
print(a.split())
print(a.split("a",2))


['aaaaa', 'bbbbb.']
['', '', '', '', '', ' bbbbb.']

• swapcase() 大写变小写 小写变大写

a = "aaaaa BBBbb"
print(a.swapcase())


AAAAA bbbBB

• upper() 变成大写

a = "aaaaa BBBbb"
print(a.upper())


AAAAA BBBBB

• casefold() 字符串全变小写

a = "aaaaa BBBbb"
print(a.casefold())

aaaaa bbbbb

• capitalize() 首字母大写，其他都变成小写

a = "aaaaa BBBbb"
print(a.capitalize())

Aaaaa bbbbb

• straswith() 判断字符串是否以指定字符或子字符串开头。返回值为 bool

  endswith() 判断字符串是否以指定字符或子字符串结尾。返回值为 bool

• 语法：str.endswith("suffix", start, end) 或str[start,end].endswith("suffix")

  用于判断字符串中某段字符串是否以指定字符或子字符串结尾。

str = "hello,i love python"
print("1: ",str.startswith("h"))
print("2：",str.startswith("l",2,10))# 索引 llo，i lo 是否以“n”结尾。
print("3：",str.startswith(""))#空字符
print("4：",str[0:6].startswith("h")) # 只索引 hello，
print("5: ",str[0:6].startswith("e"))
print("6: ",str[0:6].startswith(""))
print("7：",str.startswith(("h","z")))#遍历元组的元素， 存在即返回True，否者返回False print("8:",str.startswith(("k","m")))

1:  True
2： True
3： True
4： True
5:  False
6:  True
7： True  

数据类型-字典

• key-value结构。

• key必须为不可变数据类型、必须唯一。

• 可存放任意多个value、可修改、可以不唯一。

• 无序。

• 查询速度快，且不受dict的大小影响。

  

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