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PYTHON - BASIC OPERATORS


Operators are the constructs which can manipulate the value of operands.

Consider the expression 4 + 5 = 9. Here, 4 and 5 are called operands and + is called operator.

Types of Operators

Python language supports the following types of operators.
  • Arithmetic Operators
  • Comparison (Relational) Operators
  • Assignment Operators
  • Logical Operators
  • Bitwise Operators
  • Membership Operators
  • Identity Operators
Let us have a look on all operators one by one.

Python Arithmetic Operators

Assume variable a holds 10 and variable b holds 20, then:
OperatorDescriptionExample
+ AdditionAdds values on either side of the operator.a + b = 30
- SubtractionSubtracts right hand operand from left hand operand.a – b = -10
* MultiplicationMultiplies values on either side of the operatora * b = 200
/ DivisionDivides left hand operand by right hand operandb / a = 2
% ModulusDivides left hand operand by right hand operand and returns remainderb % a = 0
** ExponentPerforms exponential (power) calculation on operatorsa**b =10 to the power 20
//Floor Division - The division of operands where the result is the quotient in which the digits after the decimal point are removed.9//2 = 4 and 9.0//2.0 = 4.0
Example

Assume variable a holds 10 and variable b holds 20, then:

#!/usr/bin/python
a = 21
b = 10
c = 0
c = a + b
print "Line 1 - Value of c is ", c
c = a - b
print "Line 2 - Value of c is ", c
c = a * b
print "Line 3 - Value of c is ", c
c = a / b
print "Line 4 - Value of c is ", c
c = a % b
print "Line 5 - Value of c is ", c
a = 2
b = 3
c = a**b
print "Line 6 - Value of c is ", c
a = 10
b = 5
c = a//b
print "Line 7 - Value of c is ", c

When you execute the above program, it produces the following result:

Line 1 - Value of c is 31
Line 2 - Value of c is 11
Line 3 - Value of c is 210
Line 4 - Value of c is 2
Line 5 - Value of c is 1
Line 6 - Value of c is 8
Line 7 - Value of c is 2

Python Comparison Operators

These operators compare the values on either sides of them and decide the relation among them. They are also called Relational operators.

Assume variable a holds 10 and variable b holds 20, then:
OperatorDescriptionExample
==If the values of two operands are equal, then the condition becomes true.(a == b) is not true.
!=If values of two operands are not equal, then condition becomes true.(a != b) is true.
<>If values of two operands are not equal, then condition becomes true.(a <> b) is true. This is similar to != operator.
>If the value of left operand is greater than the value of right operand, then condition becomes true.(a > b) is not true.
<If the value of left operand is less than the value of right operand, then condition becomes true.(a < b) is true.
>=If the value of left operand is greater than or equal to the value of right operand, then condition becomes true.(a >= b) is not true.
<=If the value of left operand is less than or equal to the value of right operand, then condition becomes true.(a <= b) is true.
Example

Assume variable a holds 10 and variable b holds 20, then:

#!/usr/bin/python
a = 21
b = 10
c = 0
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 not equal to b"
else:
print "Line 3 - a is equal to b"
if ( a < b ):
print "Line 4 - a is less than b"
else:
print "Line 4 - a is not less than b"
if ( a > b ):
print "Line 5 - a is greater than b"
else:
print "Line 5 - a is not greater than b"
a = 5;
b = 20;
if ( a <= b ):
print "Line 6 - a is either less than or equal to b"
else:
print "Line 6 - a is neither less than nor equal to b"
if ( b >= a ):
print "Line 7 - b is either greater than or equal to b"
else:
print "Line 7 - b is neither greater than nor equal to b"

When you execute the above program it produces the following result:

Line 1 - a is not equal to b
Line 2 - a is not equal to b
Line 3 - a is not equal to b
Line 4 - a is not less than b
Line 5 - a is greater than b
Line 6 - a is either less than or equal to b
Line 7 - b is either greater than or equal to b

Python Assignment Operators

Assume variable a holds 10 and variable b holds 20, then:
OperatorDescriptionExample
=Assigns values from right side operands to left side operandc = a + b assigns value of a + b into c
+=
Add AND
It adds right operand to the left operand and assign the result to left operandc += a is equivalent to c = c + a
-=
Subtract AND
It subtracts right operand from the left operand and assign the result to left operandc -= a is equivalent to c = c - a
*=
Multiply AND
It multiplies right operand with the left operand and assign the result to left operandc *= a is equivalent to c = c * a
/=
Divide AND
It divides left operand with the right operand and assign the result to left operandc /= a is equivalent to c = c / a
%=
Modulus AND
It takes modulus using two operands and assign the result to left operandc %= a is equivalent to c = c % a
**=
Exponent AND
Performs exponential (power) calculation on operators and assign value to the left operandc **= a is equivalent to c = c ** a
//=
Floor Division
It performs floor division on operators and assign value to the left operandc //= a is equivalent to c = c // a
Example

Assume variable a holds 10 and variable b holds 20, then:

#!/usr/bin/python
a = 21
b = 10
c = 0
c = a + b
print "Line 1 - Value of c is ", c
c += a
print "Line 2 - Value of c is ", c
c *= a
print "Line 3 - Value of c is ", c
c /= a
print "Line 4 - Value of c is ", c
c = 2
c %= a
print "Line 5 - Value of c is ", c
c **= a
print "Line 6 - Value of c is ", c
c //= a
print "Line 7 - Value of c is ", c

When you execute the above program, it produces the following result:

Line 1 - Value of c is 31
Line 2 - Value of c is 52
Line 3 - Value of c is 1092
Line 4 - Value of c is 52
Line 5 - Value of c is 2
Line 6 - Value of c is 2097152
Line 7 - Value of c is 99864

Python Bitwise Operators

Bitwise operator works on bits and performs bit by bit operation. Assume if a = 60; and b = 13; Now in binary format they will be as follows:

a = 0011 1100
b = 0000 1101
-----------------
a&b = 0000 1100
a|b = 0011 1101
a^b = 0011 0001
~a = 1100 0011

There are following Bitwise operators supported by Python language
OperatorDescriptionExample
&
Binary AND
Operator copies a bit to the result if it exists in both operands.(a & b) = 12 (means 0000 1100)
| Binary ORIt copies a bit if it exists in either operand.(a | b) = 61 (means 0011 1101)
^ Binary XORIt copies the bit if it is set in one operand but not both.(a ^ b) = 49 (means 0011 0001)
~
Binary
Ones Complement
It is unary and has the effect of 'flipping' bits.(~a ) = -61 (means 1100 0011 in 2's complement form due to a signed binary number.
<< Binary Left ShiftThe left operands value is moved left by the number of bits specified by the right operand.a << 2 = 240 (means 1111 0000)
>>
Binary Right Shift
The left operands value is moved right by the number of bits specified by the right operand.a >> 2 = 15
(means 0000 1111)
Example

#!/usr/bin/python
a = 60 # 60 = 0011 1100
b = 13 # 13 = 0000 1101
c = 0
c = a & b; # 12 = 0000 1100
print "Line 1 - Value of c is ", c
c = a | b; # 61 = 0011 1101
print "Line 2 - Value of c is ", c
c = a ^ b; # 49 = 0011 0001
print "Line 3 - Value of c is ", c
c = ~a; # -61 = 1100 0011
print "Line 4 - Value of c is ", c
c = a << 2; # 240 = 1111 0000
print "Line 5 - Value of c is ", c
c = a >> 2; # 15 = 0000 1111
print "Line 6 - Value of c is ", c

When you execute the above program it produces the following result:

Line 1 - Value of c is 12
Line 2 - Value of c is 61
Line 3 - Value of c is 49
Line 4 - Value of c is -61
Line 5 - Value of c is 240
Line 6 - Value of c is 15

Python Logical Operators

There are following logical operators supported by Python language. Assume variable a holds 10 and variable b holds 20 then:
OperatorDescriptionExample
and Logical ANDIf both the operands are true then condition becomes true.(a and b) is true.
or Logical ORIf any of the two operands are non-zero then condition becomes true.(a or b) is true.
not Logical NOTUsed to reverse the logical state of its operand.Not (a and b) is false.
Python Membership Operators

Python’s membership operators test for membership in a sequence, such as strings, lists, or tuples. There are two membership operators as explained below:
SQLSQLSQL Lite
inEvaluates to true if it finds a variable in the specified sequence and false otherwise.x in y, here in results in a 1 if x is a member of sequence y.
not inEvaluates to true if it does not finds a variable in the specified sequence and false otherwise.x not in y, here not in results in a 1 if x is not a member of sequence y.
Example

#!/usr/bin/python
a = 10
b = 20
list = [1, 2, 3, 4, 5 ];
if ( a in list ):
print "Line 1 - a is available in the given list"
else:
print "Line 1 - a is not available in the given list"
if ( b not in list ):
print "Line 2 - b is not available in the given list"
else:
print "Line 2 - b is available in the given list"
a = 2
if ( a in list ):
print "Line 3 - a is available in the given list"
else:
print "Line 3 - a is not available in the given list"

When you execute the above program it produces the following result:

Line 1 - a is not available in the given list
Line 2 - b is not available in the given list
Line 3 - a is available in the given list

Python Identity Operators

Identity operators compare the memory locations of two objects. There are two Identity operators as explained below:
OperatorDescriptionExample
isEvaluates to true if the variables on either side of the operator point to the same object and false otherwise.x is y, here is results in 1 if id(x) equals id(y).
is notEvaluates to false if the variables on either side of the operator point to the same object and true otherwise.x is not y, here is not results in 1 if id(x) is not equal to id(y).
Example

#!/usr/bin/python
a = 20
b = 20
if ( a is b ):
print "Line 1 - a and b have same identity"
else:
print "Line 1 - a and b do not have same identity"
if ( id(a) == id(b) ):
print "Line 2 - a and b have same identity"
else:
print "Line 2 - a and b do not have same identity"
b = 30
if ( a is b ):
print "Line 3 - a and b have same identity"
else:
print "Line 3 - a and b do not have same identity"
if ( a is not b ):
print "Line 4 - a and b do not have same identity"
else:
print "Line 4 - a and b have same identity"

When you execute the above program it produces the following result:

Line 1 - a and b have same identity
Line 2 - a and b have same identity
Line 3 - a and b do not have same identity
Line 4 - a and b do not have same identity

Python Operators Precedence

The following table lists all operators from highest precedence to lowest.
OperatorDescription
**Exponentiation (raise to the power)
~ + -Ccomplement, unary plus and minus (method names for the last two are +@ and -@)
* / % //Multiply, divide, modulo and floor division
+ -Addition and subtraction
>> <<Right and left bitwise shift
&Bitwise 'AND'
^ |Bitwise exclusive `OR' and regular `OR'
<= < > >=Comparison operators
<> == !=Equality operators
= %= /= //= -= += *= **=Assignment operators
is is notIdentity operators
in not inMembership operators
not or andLogical operators
Operator precedence affects how an expression is evaluated.

For example, x = 7 + 3 * 2; here, x is assigned 13, not 20 because operator * has higher precedence than +, so it first multiplies 3*2 and then adds into 7.

Here, operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom.

Example

#!/usr/bin/python
a = 20
b = 10
c = 15
d = 5
e = 0
e = (a + b) * c / d #( 30 * 15 ) / 5
print "Value of (a + b) * c / d is ", e

e = ((a + b) * c) / d # (30 * 15 ) / 5
print "Value of ((a + b) * c) / d is ", e

e = (a + b) * (c / d); # (30) * (15/5)
print "Value of (a + b) * (c / d) is ", e

e = a + (b * c) / d; # 20 + (150/5)
print "Value of a + (b * c) / d is ", e

When you execute the above program, it produces the following result:

Value of (a + b) * c / d is 90
Value of ((a + b) * c) / d is 90
Value of (a + b) * (c / d) is 90
Value of a + (b * c) / d is 50
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