1, bool value types only two values (True, False)
# Boolean value
Conversion between the three types of data str int bool
str () int () bool () function itself is built
str ----> int a = "6484684" element must be a number, otherwise an error
str -----> bool empty string is not empty all False True
int -----> bool 0 is False, True all non 0
bool ---> int True 1 False is 0
bool---->str "True" , " False"
2.
# comparison operators
> < >= <= !=
== comparison values are the same two objects
is the comparison is the same memory address
Look at
memory address method id (Object)
3, logical operators and or not
x and y, x is true, the value is y, x is false, the value of x
x or y, x is true, that is, the value of x, x is false, y is the value
Comparison operator precedence over logical operators
()>not >and >or
If the priority at the same level, from left to right execution
4, 算数运算符 + - * / %取余 ** 平方 // 取整
5, 成员运算符 in, not in
现在学的只有字符串 x in y, y中是否包含x
6, 赋值运算符
= += -= *= /= %= **= //=
复合赋值运算符
在python中这种对a进行加法之后再赋值给a的情况,我们叫做
自加,常见的操作当然还有自减
a = 6
a +=1
a -=3
学到的内置函数
print()
input()
type()
int()
str()
bool()
id()
小数据池: 只在str,int中存在的
小数据池作用:(为了节省内存而存在)
数据
-5 ---256 之间的值共用一个内存地址
str ,空 或者一位(包括特殊字符) 也是共用一个内存
如果多位并且包括特殊字符不共用内存
为空时,true
在python交互式时,变量可以直接输出,不用借助print