if statement in python

The if statement is the simplest form of decision control statement that is frequently used in decision making. An if statement is a selection control statement based on the value of a given Boolean expression.

The general form of a simple if statement is shown below.

if test_expression:
    statement 1
    ..........
    statement n
statement x

The if structure may include 1 statement or n statement enclosed within the if block. First the test expression is evaluated. If the test expression is True, the statement of if block (statement 1 to n) are executed otherwise these statements will be skipped and the execution will jump to statement x.

Let’s write a program that increment a number if it is positive.

x = 10  # initialize the value of x
if (x > 0): # test the value of x
    x = x + 1 # increment the value of x if it is > 0
print(x) # print the value of x

#output
11

In the above code, we take a variable x and initialize it to 10. In the test expression we check if the value of x is greater than 0. If the test expression evaluates to True, then the value of x is incremented. Then the value of x is printed on the screen.

Observe that the print statement will be executed even if the test expression is False. Python uses indentation to form a block of code.