Conditional statements

In Python, conditional statements are used to determine if a specific condition is met by testing whether a condition is true or false. Conditional statements are used to determine how a program is executed. For example, conditional statements could be used to determine whether it is time to turn on the lights. The syntax is as follows:

if condition_is_true:

  do_something()

The condition is usually tested using a logical operator, and the set of tasks under the indented block is executed. Let's consider the example, check_address_if_statement.py (available for download with this chapter) where the user input to a program needs to be verified using a yes or no question:

check_address = input("Is your address correct(yes/no)? ") 
if check_address == "yes": 
  print("Thanks. Your address has been saved") 
if check_address == "no": 
  del(address) 
  print("Your address has been deleted. Try again")

In this example, the program expects a yes or no input. If the user provides the input yes, the condition if check_address == "yes" is true, the message Your address has been saved is printed on the screen.

Likewise, if the user input is no, the program executes the indented code block under the logical test condition if check_address == "no" and deletes the variable address.