python中的成员函数 python成员运算符有哪些

运算符 (Operators)

运算符用于对变量和值执行运算。

Python将运算符分为以下几类：

• 算术运算符 (Arithmetic operators)
• 赋值运算符 (Assignment operators)
• 比较运算符 (Comparison operators)
• 逻辑运算符 (Logical operators)
• 身份运算符 (Identity operators)
• 成员运算符 (Membership operators)
• 位运算符(Bitwise operators)

算术运算符

算术运算符与数值一起使用以执行常见的数学运算：

2**3

8

2**3.0

8.0

2.0**3 # 幂 - 返回x的y次幂

8.0

1/2

0.5

int(1/2)

0

1//2 # 取整除 - 返回商的整数部分（向下取整）

0

9//2

4

-9//2

-5

1%2 # 取模 - 返回除法的余数

1

3%2

1

4%2

0

Python赋值运算符

赋值运算符用于为变量赋值：

x=5

x+=3 # 加法赋值运算符 x=x+3
print(x)

8

print(x)
x-=3 # 减法赋值运算符
print(x)

8
5

print(x)
x*=3 # 乘法赋值运算符
print(x)

5
15

x/=3 # 除法赋值运算符
print(x)

5.0

x%=3 # 取模赋值运算符
print(x)

2.0

x**=3 # 幂赋值运算符
print(x)

8.0

x=5  # 0101
x&=3  # 0011
print(x) # 0001

1

x=5  # 0101
x|=3 # 0011
print(x) #0111

7

x=5 # 0101
x^=3 # 0011
print(x) # 0110

6

x=10 # 1010
x>>=3
print(x) # 0001

1

x=3 # 0011
x<<=3
print(x) # 11000

24

比较运算符

比较运算符用于比较两个值：

x = 6
y = 2

# equal to
print(x == y)    # False

False

# not equal to
print(x != y)    # True

True

# greater than
print(x > y)    # True

True

# less than
print(x < y)    # False

False

# greater than or equal to
print(x >= y)    # True

True

逻辑运算符

x=7
print(x> 5 and x< 10)

True

print(x<5 or x < 4)

False

print(not(x<5 and x< 10))

True

身份运算符 （Identity Operators）

a = 10
b = 10
 
if ( a is b ):
   print("Same identiy")
else:
   print("Not same identity")
 
if ( a is not b ):
   print("Not sameame identy")
else:
   print("Same identity")

print(id(a))
print(id(b))

Same identiy
Same identity
140716488237744
140716488237744

# 修改变量 b 的值
b = 20
if ( a is b ):
   print("same identiy")
else:
   print("Not same identity")
 
if ( a is not b ):
   print("Not same identy")
else:
   print("Same identity")

print(id(a))
print(id(b))

Not same identity
Not same identy
140716488237744
140716488238064

==和is之间的选择

== 运算符比较两个对象的值（对象中保存的数据），而 is 比较对象的标识。is 用于判断两个变量引用对象是否为同一个(同一块内存空间)，

通常，我们关注的是值，而不是标识，因此 Python 代码中 == 出现的频率比 is 高。

然而，在变量和单例值之间比较时，应该使用 is。比如： is 检查变量绑定的值是不是 None。可以写为：x is None ;否定的正确写法是：x is not None

x = [1, 2, 3]
y = [1, 2, 3]

print(id(x))
print(id(y))

2371673022216
2371652384904

# is
print(x is y)    # False

False

# is not
print(x is not y)  # True

True

a = [1, 2, 3]
b = a
b is a 

print(id(a))
print(id(b))

2371673020616
2371673020616

b == a

True

b = a[:]
print(b)
b is a

[1, 2, 3]





False

b == a

True

成员运算符

L = ['red', 'green', 'blue']

# in
print('red' in L)    # True

True

# not in
print('yellow' not in L)    # True

True

位运算符

x = 0b1100
y = 0b1010

# and
print(bin(x & y))    # 0b1000

0b1000

# or
print(bin(x | y))    # 0b1110

0b1110

# xor
print(bin(x ^ y))    # 0b0110

0b110

# not
print(x)   # 12; 0b1100
print(bin(x))
print(bin(~x))    # -0b1101
print(~x)

12
0b1100
-0b1101
-13

# shift 2 bits left
print(bin(x << 2))  # 0b1100

0b110000

# shift 2 bits right
print(bin(x))
print(bin(x >> 2))  # 0b0011

0b1100
0b11

a = 60            # 60 = 0011 1100 
b = 13            # 13 = 0000 1101

c = a & b;        # 12 = 0000 1100 按位与运算符
print(c)

12

c = a | b;        # 61 = 0011 1101  按位或运算符
print(c)

61

c = a ^ b;        # 49 = 0011 0001  按位异或运算符
print(c)

49

c = ~a;           # -61 = 1100 0011    按位取反运算符
print(c)

-61

#  左移动运算符：运算数的各二进位全部左移若干位，由 << 右边的数字指定了移动的位数，高位丢弃，低位补0。
c = a << 2;       # 240 = 1111 0000
print(c)

240

# 右移动运算符：把">>"左边的运算数的各二进位全部右移若干位，>> 右边的数字指定了移动的位数
c = a >> 2;       # 15 = 0000 1111
print(c)

15

运算符优先级

a = 20
b = 10
c = 15
d = 5
e = 0

e = (a + b) * c / d       #( 30 * 15 ) / 5
print(e)

90.0

e = ((a + b) * c) / d     # (30 * 15 ) / 5
print(e)

90.0

e = (a + b) * (c / d);    # (30) * (15/5)
print(e)

90.0

e = a + (b * c) / d;      #  20 + (150/5)
print(e)

50.0