Python学习-day4

Python 语言的运算符:

• 算术运算符
• 比较（关系）运算符
• 赋值运算符
• 逻辑运算符
• 位运算符
• 成员运算符
• 身份运算符
• 运算符优先级

算术运算符

定义变量a = 21，变量b = 10。

a = 21
b = 10
print("a + b =", a+b)
print("a - b =", a-b)
print("a * b =", a*b)
print("a / b =", a/b)
print("a % b =", a%b)
print("a ** b =", a**b)
print("a // b =", a//b)

a + b = 31
a - b = 11
a * b = 210
a / b = 2.1
a % b = 1
a ** b = 16679880978201
a // b = 2

比较运算符

定义变量a = 10，变量b = 20。

a = 10
b = 20
print("(a == b) =", (a == b))
print("(a != b) =", (a != b))
print("(a > b) =", (a > b))
print("(a < b) =", (a < b))
print("(a >= b) =", (a >= b))
print("(a <= b) =", (a <= b))

(a == b) = False
(a != b) = True
(a > b) = False
(a < b) = True
(a >=> b) = False
(a <= b) = True

赋值运算符

定义变量a = 10，变量b = 20。

a = 10
b = 20
c = 0c = a + b
print("c = (a + b) =", c)c += a
print("c = ( c += a) =", c)c -= a
print("c = (c -= a) =", c)c *= a
print("c = (c *= a) =", c)c /= a
print("c = (c /= a) =",  c)c = 2
c %= a
print("c = (c %= a) =", c)c **= a
print("c = (c ** = a) =", c)c //= a
print("c = (c //= a) =", c)

c = (a + b) = 30
c = ( c += a) = 40
c = (c -= a) = 30
c = (c *= a) = 300
c = (c /= a) = 30.0
c = (c %= a) = 2
c = (c ** = a) = 1024
c = (c //= a) = 102

位运算符

按位运算符是把数字看作二进制来进行计算的。
定义变量 a = 60，b = 13。

a = 60
b = 13print("a & b =", a&b)
print("a | b =", a|b)
print("a ^ b =", a^b)
print("~ a =", ~a)
print("a << 2 =", a<<2)
print("a >> 2 =", a>>2)

a & b = 12
a | b = 61
a ^ b = 49
~ a = -61
a << 2 = 240
a >> 2 = 15

逻辑运算符

定义变量 a = 10, b = 20。

a = 10
b = 20
c = 0print("a and b =", a and b)
print("a or b =", a or b)
print("not c =", not c)

a and b = 20
a or b = 10
not c = True

成员运算符

a = 10
b = 20
list = [1, 2, 3, 4, 5 ];print("a in list =", a in list)
print("b not in list =", b not in list)

a in list = False
b not in list = True

身份运算符

身份运算符用于比较两个对象的存储单元。

注：
id() 函数用于获取对象内存地址。
is 与 ==的 区别：is 用于判断两个变量引用对象是否为同一个， == 用于判断引用变量的值是否相等。

a = 20
b = 20print("a is b =", a is b)
print("a is not b =", a is not b)
print("id(a) == id(b) =", id(a) == id(b))
print("id(a) != id(b) =", id(a) != id(b))
print("a == b =", a == b)b = 30
print("\n")
print("a is b =", a is b)
print("a is not b =", a is not b)
print("id(a) == id(b) =", id(a) == id(b))
print("id(a) != id(b) =", id(a) != id(b))
print("a == b =", a == b)

a is b = True
a is not b = False
id(a) == id(b) = True
id(a) != id(b) = False
a == b = True

a is b = False
a is not b = True
id(a) == id(b) = False
id(a) != id(b) = True
a == b = False

运算符优先级，从最高到最低优先级的所有运算符

1. (expressions…)，圆括号的表达式
2. x[index], x[index:index], x(arguments…),x.attribute，读取，切片，调用，属性引用
3. **，指数 (最高优先级)
4. ~、+、- ，按位翻转, 一元加号和减号 (最后两个的方法名为 +@ 和 -@)
5. *、/、%、// ，乘，除，取模和取整除
6. +、-，加法减法

7. 、<<，右移，左移运算符

8. &，位 ‘AND’
9. ^、|，位运算符
10. <=、<、>、>=，比较运算符
11. <>、==、!=，等于运算符
12. =、%=、/=、//=、-=、+=、*=，赋值运算符
13. is、is not，身份运算符
14. in、not in，成员运算符
15. not、and or，逻辑运算符