6. Operators

6. Operators - 15 mins read

What is an operator?
Different type of operators
Arithmetic Operators
Assignment operator
Unary minus operator
Relational operators
Logical operators
Membership operators
Identity operators
Programs

6. Operators

What is an operator?

An operator is a symbol that performs an operation.
An operator acts on some variables, those variables are called operands.
If an operator acts on a single operand, then it is called a unary operator
If an operator acts on 2 operands, then it is called a binary operator.
If an operator acts on 3 operands, then it is called a ternary operator.

Program operator and operands

Name demo1.py

a = 10

b = 20

c = a + b

print(c)

output

Here a, b and c are called as operands,
+ is called as operator.

Different type of operators

Arithmetic Operators: (+, -, *, /, %, **, //)
Assignment Operator (=)
Unary minus Operator (-)
Relational Operator (>, <, >=, <=, ==, ! =)
Logical Operators (and, or, not)
Membership operators (in, not in)
Identity operators (is, is not)

Make a note:

Python does not have increment and decrement operators.

1. Arithmetic Operators: (+, -, *, /, %, **, //)

These operators do their usual job, so please don’t expect any surprises.

Assume that,

a = 13

b = 5

Operator	Meaning	Example	Result
+	Addition	a+b	18
-	Subtraction	a-b	8
*	Multiplication	a*b	65
/	Division	a/b	2.6
%	Modulus (Remainder of division)	a%b	3
**	Exponent operator (exponential power value)	a**b	371293
//	Integer division (gives only integer quotient)	a//b	2

Make a note

Division operator / always performs floating point arithmetic, so it returns float values.
Floor division (//) can perform both floating point and integral as well,

If values are int type, then the result is int type.
If at least one value is float type, the result is float type.

Program Arithmetic Operators

Name demo2.py

a = 13

b = 5

print(a+b)

print(a-b)

print(a*b)

print(a/b)

print(a%b)

print(a**b)

print(a//b)

Output

2.6

371293

2. Assignment operator: (=, +=, -=, *=, /=, %=, **=, //=)

ü By using these operators, we can assign values to variables.

Assume that,

a = 13

b = 5

Operator	Example	Equals to	Result
=	x=a+b	x = a + b	18
+=	a+=5	a = a+5	18
-=	a-=5	a = a-5	8

Program Assignment operator

Name demo3.py

a=13

print(a)

a+=5

print(a)

Output

3. Unary minus operator: (-)

Symbol of unary minus operator is –
When this operator before a single variable then it brings the corresponding results

Program Unary minus operator

Name demo4.py

a=10

print(a)

print(-a)

Output

-10

4.Relational operators (>, >=, <, <=, ==, !=)

These operators are used to compare two values.
These operators bring boolean result as True and False while comparing the values.
By using these operators, we can construct simple conditions.

Assume that,

a = 13

b = 5

Operator	Example	Result
>	a>b	True
>=	a>=b	True
<	a<b	False
<=	a<=b	False
==	a==b	False
!=	a!=b	True

Program Relational operators

Name demo5.py

a = 13

b = 5

print(a>b)

print(a>=b)

print(a<b)

print(a<=b)

print(a==b)

print(a!=b)

Output

True

False

True

5. Logical operators (and, or, not)

In python there are three logical operators those are,

Logical operators are useful to construct compound conditions.
Compound condition is a combination of more than one simple conditions.
Each simple condition brings the boolean result finally the total compound condition evaluates either True or False.

Make a note

In case of logical operators,

False indicates 0
True indicates any other number.

For boolean types behaviour

ü and

o If both arguments are True, then only result is True

ü or

o If at least one argument is True, then result is True

ü not

o complement

Program Logical operators on boolean data types

Name demo6.py

a = True

b = False

print(a and a)

print(a or b)

print(not a)

Output

True

False

Logical operators (and, or, not) on non-boolean data types behavior

Suggestion: Please understand these below statements carefully,

and operator

ü A and B returns A, if A is False.

ü A and B returns B, if A is not False.

Info

ü 0 means False

ü Any other number means True

Example 1

ü 0 and 4 returns 0

ü 5 and 7 returns 7

Example 2

ü 21 and 0 returns 0

ü 15 and 8 returns 8

Program Logical operators on non-boolean types

Name demo7.py

print(0 and 4)

print(5 and 7)

Output

Program Logical operators on non-boolean types

Name demo8.py

print(21 and 0)

print(15 and 8)

Output

Program Logical operators on non-boolean types

Name demo9.py

x = 0

y = 4

a = 4

b = 7

print(x and y)

print(a and b)

Output

Program Logical operators on non-boolean types

Name demo10.py

x=21

y=0

a=15

b=8

print(x and y)

print(a and b)

Output

Conclusion

Operator	Example	Meaning
and	x and y	ü If x is False, it returns x, otherwise it returns y

or operator

ü A or B returns A, if A is True.

ü A or B returns B, if A is not True.

Info

ü 0 means False

ü Any other number means True

Example 1

ü 0 or 4 returns 0

ü 5 or 7 returns 7

Example 2

ü 21 or 0 returns 21

ü 15 or 8 returns 8

Program Logical operators on non-boolean types

Name demo11.py

print(0 or 4)

print(5 or 7)

Output

Program Logical operators on non-boolean types

Name demo12.py

print(21 or 0)

print(15 or 8)

Output

Program Logical operators on non-boolean types

Name demo13.py

x = 0

y = 4

a = 5

b = 7

print(x or y)

print(a or b)

Output

Program Logical operators on non-boolean types

Name demo14.py

x=21

y=0

a=15

b=8

print(x or y)

print(a or b)

Output

Conclusion

Operator	Example	Meaning
or	x or y	ü If x is False, it returns y, otherwise it returns x

not operator

ü not A returns False, if A is True

ü not A returns True, if A is False

Info

ü 0 means False

ü Any other number means True

Example 1

ü not 5 returns False

ü not 0 returns True

Program not operator on non-boolean types

Name demo15.py

print(not 5)

print(not 0)

output

False

True

Program not operator on non-boolean types

Name demo16.py

x = 5

y = 0

print(not x)

print(not y)

output

False

True

Conclusion

Operator	Example	Meaning
not	not x	ü If x is False, it returns True, otherwise False

Logical operators (and, or, not)

Operator	Example	Meaning
and	x and y	ü If x is False, it returns x, otherwise it returns y
or	x or y	ü If x is False, it returns y, otherwise it returns x
not	not x	ü If x is False, it returns True, otherwise False

7. Membership operators

ü Membership operators are useful to check whether the given object is available in collection (sequence) or not. (It may be string, list, set, tuple and dict)

ü There are two membership operators,

o in

o not in

The in operator

ü in operator returns True, if element is found in the collection or sequences.

ü in operator returns False, if element is not found in the collection or sequences.

The not in operator

ü This work in reverse manner for ‘in’ operator.

ü not in operator returns True, if an element is not found in the sequence.

ü not in operator returns False, if an element is found in the sequence.

Program example by using in and not in operator

Name demo17.py

text = “Welcome to python programming”

print(“Welcome” in text)

print(“welcome” in text)

print(“nireekshan” in text)

print(“Hari” not in text)

output

True

False

True

Program example by using in and not in operator

Name demo18.py

names = [“Ramesh”, “Nireekshan”, “Arjun”, “Prasad”]

print(“Nireekshan” in names)

print(“Hari” in names)

print(“Hema” not in names)

output

True

False

True

8. Identity operators

ü This operator compares the memory locations (address) of two objects.

ü Hence, it is possible to know whether the two objects are pointing to same object or not.

ü The memory locations of an object can be seen by using id() function.

Program Checking two variables address by using id() function

Name demo19.py

a=25

b=25

print(a)

print(b)

print(id(a))

print(id(b))

Output

1570989024

There are two identity operators

1. is

2. is not

ü We can use identity operators for address comparison.

ü We can use id() predefined function to check the address of every element.

is operator

ü A is B returns True, if both A and B are pointing to the same object.

ü A is B returns False, if both A and B are not pointing to the same object.

is not operator

ü A is not B returns True, if both A and B are not pointing to the same object.

ü A is not B returns False, if both A and B are pointing to the same object.

Make a note

ü The ‘is’ and ‘is not’ operators are not comparing the values of the objects.

ü They compare the memory locations (address) of the objects.

ü If we want to compare the value of the objects, we should use equality operators (==).

Program example by using is operator

Name demo20.py

a = 25

b = 25

print(a is b)

print(id(a))

print(id(b))

Output

True

1416520672

Program example by using is operator

Name demo21.py

a = 25

b = 30

print(a is b)

print(id(a))

print(id(b))

Output

False

1420977120

1420977280

Program example by using == operator

Name demo22.py

a = 25

b = 25

print(a == b)

output

True

Program example by using == operator

Name demo23.py

a = 25

b = 30

print(a == b)

output

False

Program example by using is not operator

Name demo24.py

a = 25

b = 25

print(a is not b)

output

False

Monday, 29 April 2019

6. Operators

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