In our previous code examples, we have been writing code that executes sequentially - line by line. It omitted comments and blank lines but executed every single line of code written.
In some cases, we might want to execute a block of code only if some conditions are met.
Imagine if we want to buy water from a store if our thirst level is below 30 (in this case, thirst is measured as a number from 0 to 100). To buy a bottle of water we would make a payment. In python, conditional operations can be written through if statements:
Here the program reads the thirst level and the price of a bottle.
Then the if statement checks if the thirst levels are below 30, and in case they are, it makes the payment and fulfills the thirst by setting the level to 100.
In the end, the program prints how much was paid and the resulting thirst level.
if statements have conditions followed by a :. In case the statement holds, the contents of the if block is evaluated. Note that the operations are indented with 4 spaces and are shifted by 4 spaces from the start of a line. They need to be “inside” the if block to be executed if the condition holds.
The condition of the if statement is evaluated to be either True or False. So, it’s a boolean value. In case that value is evaluated to True (meaning the condition holds), the content of the if block is executed.
Write a program that would read a single integer from the input and print This number is even in case it was even, and The end of the program in the end.