Python căn bản (10): Python Operators

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10. Python Operators

10.1 Operators

Operators are used to perform operations on variables and values.

In the example below, we use the + operator to add together two values.

Example

print(10 + 5)

Python divides the operators in the following groups:

- Arithmetic operators

- Assignment operators

- Comparison operators

- Logical operators

- Identity operators

- Membership operators

- Bitwise operators

Python Arithmetic Operators

Arithmetic operators are used with numeric values to perform common mathematical operations.

Operator         Name                         Example

+                      Addition                     x + y   

-                       Subtraction               x - y    

*                       Multiplication                        x * y    

/                       Division                     x / y    

%                     Modulus                    x % y  

**                     Exponentiation         x ** y  

//                      Floor division                        x // y

Python Assignment Operators

Assignment operators are used to assign values to variables.

Operator         Example        Same As

=                      x = 5                x = 5   

+=                    x += 3             x = x + 3        

-=                     x -= 3              x = x - 3         

*=                    x *= 3              x = x * 3         

/=                     x /= 3               x = x / 3          

%=                  x %= 3            x = x % 3       

//=                    x //= 3              x = x // 3         

**=                   x **= 3             x = x ** 3        

&=                   x &= 3             x = x & 3        

|=                     x |= 3               x = x | 3          

^=                    x ^= 3              x = x ^ 3         

>>=                 x >>= 3           x = x >> 3      

<<=                 x <<= 3           x = x << 3      

:=                     print(x := 3)    x = 3; print(x)

Python Comparison Operators

Comparison operators are used to compare two values.

Operator         Name                         Example

==                    Equal                         x == y 

!=                     Not equal                   x != y  

>                      Greater than              x > y   

<                      Less than                  x < y   

>=                    Greater than or equal to      x >= y 

<=                    Less than or equal to          x <= y

Python Logical Operators

Logical operators are used to combine conditional statements.

Operator         Description                            Example

and     Returns True if both statements are true             x < 5 and  x < 10      

or         Returns True if one of the statements is true     x < 5 or x < 4 

not      Reverse the result, returns False if the result is true     not(x < 5 and x < 10)

Python Identity Operators

Identity operators are used to compare the objects, not if they are equal, but if they are actually the same object, with the same memory location.

Operator         Description                            Example

is         Returns True if both variables are the same object       x is y  

is not  Returns True if both variables are not the same object                        x is not y

Example

x = ["apple", "banana"]

y = ["apple", "banana"]

z = x

 

print(x is z)

# returns True because z is the same object as x

 

print(x is y)

# returns False because x is not

# the same object as y, even if they have the same

Python Membership Operators

Membership operators are used to test if a sequence is presented in an object.

Operator                     Description                Example

in         Returns True if a sequence with the specified value is present in the object                      x in y

not in  Returns True if a sequence with the specified value is not present in the object   x not in y

Example

x = ["apple", "banana"]

 

print("banana" in x)

 

# returns True because a sequence with

# the value "banana" is in the list

Python Bitwise Operators

Bitwise operators are used to compare (binary) numbers.

Operator         Name             Description    Example

&         AND   Sets each bit to 1 if both bits are 1            x & y  

|           OR      Sets each bit to 1 if one of two bits is 1    x | y    

^          XOR   Sets each bit to 1 if only one of two bits is 1       x ^ y   

~          NOT    Inverts all the bits                 ~x       

<<        Zero fill left shift       Shift left by pushing zeros in from the right and let the leftmost bits fall off x << 2   

>>        Signed right shift     Shift right by pushing copies of the leftmost bit in from the left, and let the rightmost bits fall off            x >> 2

Operator Precedence

Operator precedence describes the order in which operations are performed.

Example

Parentheses have the highest precedence, meaning that expressions inside parentheses must be evaluated first.

print((6 + 3) - (6 + 3))

Example

Multiplication * has higher precedence than addition +, and therefore multiplications are evaluated before additions.

print(100 + 5 * 3)

The precedence order is described in the table below, starting with the highest precedence at the top.

Operator                     Description

()                      Parentheses

**                     Exponentiation        

+x  -x  ~x        Unary plus, unary minus, and bitwise NOT       

*  /  //  %          Multiplication, division, floor division, and modulus    

+  -                   Addition and subtraction   

<<  >>             Bitwise left and right shifts

&                     Bitwise AND

^                      Bitwise XOR

|                       Bitwise OR   

==  !=  >  >=  <  <=  is  is not  in  not in      Comparisons, identity, and membership operators      

not                  Logical NOT 

and                 AND  

or                     OR

If two operators have the same precedence, the expression is evaluated from left to right.

Example

Addition + and subtraction - has the same precedence, and therefore we evaluate the expression from left to right.

print(5 + 4 - 7 + 3)

10. Exercise

1. What will be the result of the following code:

x = 5

x += 3

print(x)

A. 3

B. 5

C. 8

D. True

2. What will be the result of the following code:

print(2 * 0 == 2 and 2 ** 3  == 8)

A. True

B. 3

C. 8

D. False

3. What will be the result of the following code:

print(2 * 0 == 2 or 2 ** 3  == 8)

A. True

B. 3

C. 8

D. False

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The answer hints:

1(C), 2(D), 3(A)

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Cập nhật: 19/10/2024

Bài sau: Python căn bản (11): Python If ... Else

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