Python Projects for Beginners a ten-Week Bootcamp Approach to Python Programming

How They Work

Every day you make hundreds of decisions. These decisions define what you do with your day. In programming these are known as branching statements or “if statements.” An if statement works the same way that a decision is made. You check a condition, and if that condition is true, you perform the task, and if it’s not true, then you move on without performing that task:
“Am I hungry?”
“Yes, so I should make some food.”
*** proceeds to cook food ***
The same decision-making process can be implemented in programming using an if statement.

Writing Your First If Statement

All branching statements begin the same way, with the keyword “if”. Following the keyword is what is known as a condition. Lastly, there will always be an ending colon at the end of the statement. The if statement checks to see if the given condition is True or False. If the condition is True, then the code block runs. If it is False, then the program continues without running any of the code indented directly after the if statement. Let’s try it out:

# using an if statement to only run code if the condition is met x, y = 5, 10 if x < y: print("x is less than y")

Go ahead and run that cell. Notice here that the output is “x is less than y”. This is because we originally declared x equal to 5 and y equal to 10 and then used an if statement to check if x was less than y, which it was. If x was equal to 15, then the print statement indented after the “if” would have never ran, because the condition would have been False.
ChApTer 3 User InpUT And CondITIonAls

Comparison Operators

Before we continue with branching statements, we need to go over comparison operators. So far, we’ve used arithmetic operators for adding and subtracting values and assignment operators for declaring variables, and with the introduction of the “if statement,” we’ve now seen comparison operators. There are several comparisons that you’re able to make. Most comparison operators that you’ll use, however, are shown in Table 3-2.
Table 3-2. Comparison operators