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Similar to C, C++ and Java programming languages, Python also gives us a feature of the conditional operator, which is also called ternary operator because it has three operands, such as:

• First expression.
• if boolean-condition.
• else statement with a second expression.

Syntax of the conditional operator -

first-expression  if boolean-condition  else second-expression

Rules of the conditional operator -



• If the result of a boolean-condition associated with the if statement is true, the first expression will be executed and its value is returned.
• If the result of a boolean-condition associated with the if statement is false, the second expression associated with the else statement will be executed and its value is returned.
• Both the first and second expression must result in a value.

Example of conditional operator

# Python conditional operator example

a=10	#integer variable1
b=20	#integer variable2


#Conditional expression1
large = a if a>b else b
print(large)


#Conditional expression2
str1 = 'a is less than b' if a<b  else 'a is greater than b'
print(str1)


#Conditional expression3
print(10   if a>b  else 100.50)


#Conditional expression4
print('y'  if a>b  else 'n')

Output

20
a is less than b
100.5
n

A conditional operator could even result in an object or its attribute value.




#Python conditional operator example


#Defining a class and its integer attribute
class A :
    x=5 	

	
#Initializing a variable with an object of A class
ob = A()


#Initializing a variable with a boolean 1(true) value
bool_value = 1 	


#Conditional expression1
print('yes' if 5>10 else 'no')


#Conditional expression2
print(ob if bool_value else 'Object of class A does not exist');


#Conditional expression3
print(ob.x if bool_value else 'Object of class A does not exist');





Output is




no
<__main__.A object at 0x0000000002ED67B8>
5


In the above example, we have created an object of class A. In the conditional expression2, we have got the representation of the object's address in the memory, by printing this object. In the conditional expression3, we have got the value of object's attribute i.e. 5.




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A conditional operator returning a string value.




#Conditional expression returning a string value


#Conditional expression1
print('5 is greater than 10'  if 5>10 else '10 is greater than 5')

#Conditional expression2
print('a is greater than b' if 'a'>'b' else 'b is greater than a')





Output is




10 is greater than 5
b is greater than a








Either expression of a conditional operator cannot be left blank




#Python conditional operator example


a=10	#integer variable1
b=20	#integer variable2


#First expression of this conditional operator is missing
print( if a>b else 20)



The above program on execution throws an error i.e. Invalid Syntax because we have not mentioned the first expression of the conditional operator and it is left blank. Note: Both the first and second expression associated with the if-else construct should be mentioned or an error is thrown.






An expression of conditional operator could be a None keyword.




#Python conditional operator example


a,b = 10,5	#Assigning 10 to a and 5 to b


#Conditional operator expression
print(10 if a>b else 5)


#Second conditional operator expression
print("a is less than b" if a<b else None);





Output is




10
None


An expression of a conditional operator could even be a None, where None keyword can be assigned to any variable or an object to signify that the variable/object doesn't have any value.






An expression of a conditional operator can be a method call.

Any expression of a conditional operator could even be a call to a method but this method must return a value.

#Defining a class Flower with two functions
class Flower :
        #First function 
        def hasAFlower(self):
                return 1

        #Second function
        def getColor(self):
                return "The color of this flower is blue"
        

#Creating an object of class Flower
ob = Flower()


#Conditional expression
print(ob.getColor() if ob.hasAFlower() else 'Does not have a flower')

Output-

The color of this flower is blue

In this last program, the condition of if statement in the conditional operator calls the function hasAFlower(), which returns 1 i.e. true boolean value, hence the first expression of the conditional operator, which is a call to a function getColor() is executed, which returns a string i.e. The color of flower is blue.

Note: If you don't use self keyword in function definitions then the following error is thrown by the compiler- TypeError: getColor() takes 0 positional arguments but 1 was given.

In a way, the self keyword of Python is similar to this keyword of Java language, and theself keyword must be included when defining a method of a class, to represent the current instance of a class.

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