Python 简明教程

Python - Operators

Python Operators

Python operators 是用来对一个或多个操作数执行特定操作的特殊符号。 variables 、值或表达式可以用作操作数。例如，Python 的加法运算符 ( + ) 用于对两个变量、值或表达式执行加法操作。

Python operators are special symbols used to perform specific operations on one or more operands. The variables, values, or expressions can be used as operands. For example, Python’s addition operator (+) is used to perform addition operations on two variables, values, or expressions.

以下是与 Python operators 相关的一些术语：

The following are some of the terms related to Python operators:

Unary operators: Python operators that require one operand to perform a specific operation are known as unary operators.
Binary operators: Python operators that require two operands to perform a specific operation are known as binary operators.
Operands: Variables, values, or expressions that are used with the operator to perform a specific operation.

Types of Python Operators

Python 运算符被归类在以下类别中 −

Python operators are categorized in the following categories −

Arithmetic Operators
Comparison (Relational) Operators
Assignment Operators
Logical Operators
Bitwise Operators
Membership Operators
Identity Operators

让我们逐个查看所有运算符。

Let us have a look at all the operators one by one.

Python Arithmetic Operators

Python Arithmetic operators 用于执行基本数学运算，例如加法、减法、乘法等。

Python Arithmetic operators are used to perform basic mathematical operations such as addition, subtraction, multiplication, etc.

下表包含所有算术运算符，以及它们的符号、名称和示例（假设 a 和 b 的值分别为 10 和 20）：

The following table contains all arithmetic operators with their symbols, names, and examples (assume that the values of a and b are 10 and 20, respectively) −

Operator

Name

Example

Addition

a + b = 30

Subtraction

a – b = -10

Multiplication

a * b = 200

Division

b / a = 2

Modulus

b % a = 0

Exponent

a*b =10*20

Floor Division

9//2 = 4

Example of Python Arithmetic Operators

a = 21
b = 10
c = 0

c = a + b
print ("a: {} b: {} a+b: {}".format(a,b,c))

c = a - b
print ("a: {} b: {} a-b: {}".format(a,b,c) )

c = a * b
print ("a: {} b: {} a*b: {}".format(a,b,c))

c = a / b
print ("a: {} b: {} a/b: {}".format(a,b,c))

c = a % b
print ("a: {} b: {} a%b: {}".format(a,b,c))

a = 2
b = 3
c = a**b
print ("a: {} b: {} a**b: {}".format(a,b,c))

a = 10
b = 5
c = a//b
print ("a: {} b: {} a//b: {}".format(a,b,c))

Output

a: 21 b: 10 a+b: 31
a: 21 b: 10 a-b: 11
a: 21 b: 10 a*b: 210
a: 21 b: 10 a/b: 2.1
a: 21 b: 10 a%b: 1
a: 2 b: 3 a**b: 8
a: 10 b: 5 a//b: 2

Python Comparison Operators

Python Comparison operators 比较两边值并判断它们之间的关系。它们也被称为关系运算符。

Python Comparison operators compare the values on either side of them and decide the relation among them. They are also called Relational operators.

下表包含所有比较运算符及其符号、名称和示例（假设 a 和 b 的值分别为 10 和 20）−

The following table contains all comparison operators with their symbols, names, and examples (assume that the values of a and b are 10 and 20, respectively) −

Operator

Name

Example

Equal

(a == b) is not true.

Not equal

(a != b) is true.

Greater than

(a > b) is not true.

Less than

(a < b) is true.

Greater than or equal to

(a >= b) is not true.

⇐

Less than or equal to

(a ⇐ b) is true.

Example of Python Comparison Operators

a = 21
b = 10
if ( a == b ):
   print ("Line 1 - a is equal to b")
else:
   print ("Line 1 - a is not equal to b")

if ( a != b ):
   print ("Line 2 - a is not equal to b")
else:
   print ("Line 2 - a is equal to b")

if ( a < b ):
   print ("Line 3 - a is less than b" )
else:
   print ("Line 3 - a is not less than b")

if ( a > b ):
   print ("Line 4 - a is greater than b")
else:
   print ("Line 4 - a is not greater than b")

a,b=b,a #values of a and b swapped. a becomes 10, b becomes 21

if ( a <= b ):
   print ("Line 5 - a is either less than or equal to  b")
else:
   print ("Line 5 - a is neither less than nor equal to  b")

if ( b >= a ):
   print ("Line 6 - b is either greater than  or equal to b")
else:
   print ("Line 6 - b is neither greater than  nor equal to b")

Output

Line 1 - a is not equal to b
Line 2 - a is not equal to b
Line 3 - a is not less than b
Line 4 - a is greater than b
Line 5 - a is either less than or equal to  b
Line 6 - b is either greater than  or equal to b

Python Assignment Operators

Python Assignment operators 用于将值分配给变量。以下表格显示了所有 Python 赋值运算符。

Python Assignment operators are used to assign values to variables. Following is a table which shows all Python assignment operators.

下表包含所有赋值运算符及其符号、名称和示例 −

The following table contains all assignment operators with their symbols, names, and examples −

Operator

Example

Same As

a = 10

a += 30

a = a + 30

a -= 15

a = a - 15

a *= 10

a = a * 10

a /= 5

a = a / 5

a %= 5

a = a % 5

**=

a **= 4

a = a ** 4

//=

a //= 5

a = a // 5

a &= 5

a = a & 5

= 5

a = a

a ^= 5

a = a ^ 5

>>=

a >>= 5

a = a >> 5

<⇐

a <⇐ 5

a = a << 5

Example of Python Assignment Operators

a = 21
b = 10
c = 0
print ("a: {} b: {} c : {}".format(a,b,c))
c = a + b
print ("a: {}  c = a + b: {}".format(a,c))

c += a
print ("a: {} c += a: {}".format(a,c))

c *= a
print ("a: {} c *= a: {}".format(a,c))

c /= a
print ("a: {} c /= a : {}".format(a,c))

c  = 2
print ("a: {} b: {} c : {}".format(a,b,c))
c %= a
print ("a: {} c %= a: {}".format(a,c))

c **= a
print ("a: {} c **= a: {}".format(a,c))

c //= a
print ("a: {} c //= a: {}".format(a,c))

Output

a: 21 b: 10 c : 0
a: 21  c = a + b: 31
a: 21 c += a: 52
a: 21 c *= a: 1092
a: 21 c /= a : 52.0
a: 21 b: 10 c : 2
a: 21 c %= a: 2
a: 21 c **= a: 2097152
a: 21 c //= a: 99864

Python Bitwise Operators

Python Bitwise operator 对位进行操作，执行逐位操作。这些算子用于比较二进制数。

Python Bitwise operator works on bits and performs bit by bit operation. These operators are used to compare binary numbers.

下表包含所有按位操作符的符号、名称和示例 −

The following table contains all bitwise operators with their symbols, names, and examples −

Operator

Name

Example

AND

a & b

XOR

a ^ b

NOT

Zero fill left shift

a << 3

Example of Python Bitwise Operators

a = 20
b = 10

print ('a=',a,':',bin(a),'b=',b,':',bin(b))
c = 0

c = a & b;
print ("result of AND is ", c,':',bin(c))

c = a | b;
print ("result of OR is ", c,':',bin(c))

c = a ^ b;
print ("result of EXOR is ", c,':',bin(c))

c = ~a;
print ("result of COMPLEMENT is ", c,':',bin(c))

c = a << 2;
print ("result of LEFT SHIFT is ", c,':',bin(c))

c = a >> 2;
print ("result of RIGHT SHIFT is ", c,':',bin(c))

Output

a= 20 : 0b10100 b= 10 : 0b1010
result of AND is  0 : 0b0
result of OR is  30 : 0b11110
result of EXOR is  30 : 0b11110
result of COMPLEMENT is  -21 : -0b10101
result of LEFT SHIFT is  80 : 0b1010000
result of RIGHT SHIFT is  5 : 0b101

Python Logical Operators

Python logical operators 用于组合两个或更多条件并检查最终结果。Python 语言支持以下逻辑运算符。假设变量 a 保存 10，变量 b 保存 20，则

Python logical operators are used to combile two or more conditions and check the final result. There are following logical operators supported by Python language. Assume variable a holds 10 and variable b holds 20 then

下表包含所有逻辑运算符的符号、名称和示例 −

The following table contains all logical operators with their symbols, names, and examples −

Operator

Name

Example

and

AND

a and b

a or b

not

NOT

not(a)

Example of Python Logical Operators

var = 5

print(var > 3 and var < 10)
print(var > 3 or var < 4)
print(not (var > 3 and var < 10))

Output

True
True
False

Python Membership Operators

Python 的 membership operators 测试序列（例如字符串、列表或元组）的成员资格。

Python’s membership operators test for membership in a sequence, such as strings, lists, or tuples.

如下所述，有两个成员资格运算符：

There are two membership operators as explained below −

Operator

Description

Example

Returns True if it finds a variable in the specified sequence, false otherwise.

a in b

not in

returns True if it does not finds a variable in the specified sequence and false otherwise.

a not in b

Example of Python Membership Operators

a = 10
b = 20
list = [1, 2, 3, 4, 5 ]

print ("a:", a, "b:", b, "list:", list)

if ( a in list ):
   print ("a is present in the given list")
else:
   print ("a is not present in the given list")

if ( b not in list ):
   print ("b is not present in the given list")
else:
   print ("b is present in the given list")

c=b/a
print ("c:", c, "list:", list)
if ( c in list ):
   print ("c is available in the given list")
else:
    print ("c is not available in the given list")

Output

a: 10 b: 20 list: [1, 2, 3, 4, 5]
a is not present in the given list
b is not present in the given list
c: 2.0 list: [1, 2, 3, 4, 5]
c is available in the given list

Python Identity Operators

Python identity operators 比较两个对象的内存地址。

Python identity operators compare the memory locations of two objects.

如下所述，有两个标识符运算符：

There are two Identity operators explained below −

Operator

Description

Example

Returns True if both variables are the same object and false otherwise.

a is b

is not

Returns True if both variables are not the same object and false otherwise.

a is not b

Example of Python Identity Operators

a = [1, 2, 3, 4, 5]
b = [1, 2, 3, 4, 5]
c = a

print(a is c)
print(a is b)

print(a is not c)
print(a is not b)

Output

True
False
False
True

Python Operators Precedence

运算符优先级决定了运算符求值执行的顺序。Python 运算符具有不同的优先级。下表包含优先级从最高到最低排列的运算符列表 −

Operators precedence decides the order of the evaluation in which an operator is evaluated. Python operators have different levels of precedence. The following table contains the list of operators having highest to lowest precedence −

下表列出了从最高 precedence 到最低的所有运算符。

The following table lists all operators from highest precedence to lowest.

Sr.No.	Operator & Description
1	** Exponentiation (raise to the power)
2	~ + - Complement, unary plus and minus (method names for the last two are +@ and -@)
3	* / % // Multiply, divide, modulo and floor division
4	+ - Addition and subtraction
5	>> << Right and left bitwise shift
6	& Bitwise 'AND'
7	*^
* Bitwise exclusive `OR' and regular `OR'	8
⇐ < > >= Comparison operators	9
<> == != Equality operators	10
= %= /= //= -= += = =* Assignment operators	11
is is not Identity operators	12
in not in Membership operators	13

在此处详细了解 Python 运算符优先级： Python operators precedence

Read more about the Python operators precedence here: Python operators precedence