Day2_python知识点

一、错误案例

1.注意中英文双引号，编程中用英文

二、python知识点

今日内容：
 
 python开发IDE： pycharm、eclipse
 
 # 专业版
 # 不要汉化
 
 1、运算符
  结果是值
   算数运算
    a = 10 * 10
   赋值运算
    a = a + 1    a+=1

  结果是布尔值
   比较运算
    a = 1 > 5
   逻辑运算
    a = 1>6 or 1==1
   成员运算
    a = "蚊" in "郑建文"
  
 2、基本数据类型
 
 
  数字  int ，所有的功能，都放在int里
   a1 = 123
   a1 = 456
   
   - int
    将字符串转换为数字
     a = "123"
     print(type(a),a)

     b = int(a)
     print(type(b),b)
     
     num = "0011"
     v = int(num, base=16)
     print(v)
   - bit_lenght
     # 当前数字的二进制，至少用n位表示
     r = age.bit_length()
   
  字符串  str
     ###########################################

     # 1 首字母大写
      # test = "aLex"
      # v = test.capitalize()
      # print(v)

 

     # 2 所有变小写，casefold更牛逼，很多未知的对相应变小写
      # v1 = test.casefold()
      # print(v1)
      # v2 = test.lower()
      # print(v2)

 

     # 3 设置宽度，并将内容居中
      # 20 代指总长度
      # *  空白未知填充，一个字符，可有可无
      # v = test.center(20,"中")
      # print(v)

      # test = "alex"
      # v = test.ljust(20,"*")
      # print(v)

      # test = "alex"
      # v = test.rjust(20,"*")
      # print(v)

      # test = "alex"
      # v = test.zfill(20)
      # print(v)

     # 4 去字符串中寻找，寻找子序列的出现次数
      # test = "aLexalexr"
      # v = test.count('ex')
      # print(v)

      # test = "aLexalexr"
      # v = test.count('ex',5,6)
      # print(v)

 

     # 5
      # 以什么什么结尾
      # 以什么什么开始
      # test = "alex"
      # v = test.endswith('ex')
      # v = test.startswith('ex')
      # print(v)

 

     # 6 expandtabs,断句20，
      # test = "username\temail\tpassword\nlaiying\[email protected]\t123\nlaiying\[email protected]\t123\nlaiying\[email protected]\t123"
      # v = test.expandtabs(20)
      # print(v)

 

     # 7 从开始往后找，找到第一个之后，获取其未知
      # > 或 >=
      # test = "alexalex"
      # 未找到 -1
      # v = test.find('ex')
      # print(v)

 

     # 8 index找不到，报错   忽略
      # test = "alexalex"
      # v = test.index('8')
      # print(v)

     # 9 格式化，将一个字符串中的占位符替换为指定的值
      # test = 'i am {name}, age {a}'
      # print(test)
      # v = test.format(name='alex',a=19)
      # print(v)

      # test = 'i am {0}, age {1}'
      # print(test)
      # v = test.format('alex',19)
      # print(v)

 

     # 10 格式化，传入的值 {"name": 'alex', "a": 19}
      # test = 'i am {name}, age {a}'
      # v1 = test.format(name='df',a=10)
      # v2 = test.format_map({"name": 'alex', "a": 19})

 

     # 11 字符串中是否只包含 字母和数字
      # test = "123"
      # v = test.isalnum()
      # print(v)
      # str
      
     # 12 是否是字母，汉子
      # test = "as2df"
      # v = test.isalpha()
      # print(v)

 

     # 13 当前输入是否是数字
      # test = "二" # 1，②
      # v1 = test.isdecimal()
      # v2 = test.isdigit()
      # v3 = test.isnumeric()
      # print(v1,v2,v3)