Alternative Execution

The second form of if statement is alternative execution. Some programmers call this an if/else statement. In this alternative execution there are two possibilities and based on condition it determines which one gets executed. The syntax of the code looks like this:

>>>If x % 2 == 0:
…    print ‘x is even’ 
…else:
…    print ‘x is odd’ 

If the remainder when x is divided by 2 is 0, then we know that x is even, and the program displays a message to that effect. So if the condition is false the second set of statements is executed. Since the condition must be true or false, exactly one of the alternatives will be executed. The alternatives are called braches, because they are branches in the flow of execution. Here is full example of alternative execution:

>>>value = raw_input(“Enter a value: “)
Enter a value: 45
>>>x = int(value)
>>>if x%2==0:
…      print ‘x is even’
…else: 
…      print ‘x is odd’
x is odd