Taste and Adjust (If/Else Decisions)

Once your program can ask a question with a comparison operator, you need a way to act on the true or false answer. That's what if/else statements are for. They are the fundamental decision-making tool in programming.

The structure is just like a sentence you'd use in real life:

"If the oven temperature is too high, then turn it down. Else, keep it as is."

It’s like a fork in the road for your code, guiding it to the right action. The condition you check must evaluate to either true or false.

• The code inside the if block only runs when the condition is true.
• The code inside the else block only runs when the condition is false.

Let's build on the example from the last section. Instead of just printing true or false, we can print a more helpful message.

internal_temp = 170

if internal_temp >= 165:
  print("The dish is perfectly cooked! Ready to serve.")
else:
  print("The dish needs more time to cook. Keep cooking!")

let internalTemp = 170;

if (internalTemp >= 165) {
  console.log("The dish is perfectly cooked! Ready to serve.");
} else {
  console.log("The dish needs more time to cook. Keep cooking!");
}

Now, try changing the internal_temp (or internalTemp) to something less than 165, like 150, and run the code again. You'll see the program take the other path and execute the code inside the else block instead. This is how you make your programs dynamic and responsive, just like a chef adjusting their cooking based on observations!

The Goldilocks Problem (Multi-Path Decisions)

What if you have more than two options? This is like Goldilocks tasting the porridge: one bowl is too hot, one is too cold, and one is just right. An if/else statement only gives you two paths, but you can add more paths using else if (or elif in Python).

This lets you chain conditions together:

1. if: Checks the first condition. If it's true, the code runs, and the chain is exited.
2. else if: If the first condition was false, this next condition is checked. You can have as many else if blocks as you need.
3. else: If none of the above conditions were true, this code runs as a fallback.

Let's see how to handle porridge that is too hot, too cold, or just right.

porridge_temp = 75

if porridge_temp > 85:
  print("This porridge is too hot!")
elif porridge_temp < 65:
  print("This porridge is too cold!")
else:
  print("This porridge is just right.")

let porridgeTemp = 75;

if (porridgeTemp > 85) {
  console.log("This porridge is too hot!");
} else if (porridgeTemp < 65) {
  console.log("This porridge is too cold!");
} else {
  console.log("This porridge is just right.");
}

With this structure, you can create clear and effective logic for any number of choices, ensuring your program always knows the right step to take.

Mini-Exercise 💡

Let's modify the code to assign a letter grade based on a score.

• A: score >= 90
• B: 80 <= score < 90
• C: 70 <= score < 80
• F: score < 70

Try it with a variable score = 85 and see what grade gets printed.