9 The Grail Castle Test: Mastering ‘If’ Statements

In our previous lesson, we learned about logical operators. Today, we’ll use that knowledge to enter the Grail Castle of conditional statements, focusing on the powerful ‘if’ statement. This magical construct will allow our code to make decisions, just as a knight must choose their path wisely.

9.1 What are Conditional Statements?

Imagine you’re standing at a crossroads in your quest. The path you choose depends on certain conditions - is it raining? Do you have enough provisions? Are there dragons ahead? In Python, we use conditional statements to make these kinds of decisions in our code.

The ‘if’ statement is the most basic form of conditional statement. It allows us to execute a block of code only if a certain condition is true.

9.2 The Structure of an ‘If’ Statement

Here’s the basic structure of an ‘if’ statement:

if condition:
    # Code to execute if the condition is True
    # This block is indented

Let’s break this down:

The statement starts with the keyword if.
After if, we have a condition - an expression that evaluates to either True or False.
The condition is followed by a colon :.
The next line starts an indented block of code. This block only runs if the condition is True.

9.3 Your First ‘If’ Statement

Let’s cast our first ‘if’ statement spell:

is_knight = True

if is_knight:
    print("You may enter the Grail Castle.")

print("This line always runs.")

This will output:

You may enter the Grail Castle.
This line always runs.

If we change is_knight to False, we’ll only see:

This line always runs.

9.4 Using Comparison Operators in Conditions

We often use comparison operators in our conditions. Here’s a list of these operators:

==: Equal to
!=: Not equal to
>: Greater than
<: Less than
>=: Greater than or equal to
<=: Less than or equal to

Let’s use these in some ‘if’ statements:

knight_level = 7

if knight_level >= 5:
    print("You are experienced enough for this quest.")

magic_power = 20

if magic_power > 50:
    print("You can cast a powerful spell!")

password = "Camelot"

if password == "Camelot":
    print("Access granted to the Round Table.")

9.5 Combining Conditions with Logical Operators

Remember our logical operators (and, or, not) from the previous lesson? We can use these to create more complex conditions:

has_sword = True
has_shield = False
is_brave = True

if has_sword and is_brave:
    print("You are ready to face the dragon!")

if has_sword or has_shield:
    print("You have at least one piece of equipment.")

if not has_shield:
    print("You might want to buy a shield.")

9.6 Practice Your ‘If’ Statement Magic

Now it’s your turn to practice these conditional spells:

Create a variable dragon_hp (hit points) and set it to a number. Write an ‘if’ statement that prints “The dragon is defeated!” if dragon_hp is 0 or less.
Make variables for has_sword, has_armor, and has_magic. Write an ‘if’ statement that prints “You are fully equipped!” if all three are True.
Create a player_gold variable. Write an ‘if’ statement that prints “You can buy a potion” if player_gold is at least 50.

Here’s a starting point for your practice:

# Quest 1: Defeat the Dragon
dragon_hp = 100  # Change this value to test your code
# Your code here

# Quest 2: Check Equipment
has_sword = True
has_armor = False
has_magic = True
# Your code here

# Quest 3: Buy a Potion
player_gold = 75
# Your code here

# Quest 4: Weather Check
is_day = True
is_sunny = False
# Your code here

9.7 Common Bugs to Watch Out For

As you cast your ‘if’ statement spells, beware of these common pitfalls:

Forgetting the colon: Always remember to put a colon : at the end of your ‘if’ line.
Incorrect indentation: The code block under an ‘if’ statement must be indented. Incorrect indentation can change the meaning of your code.
Using = instead of ==: Remember, = is for assignment, == is for comparison.
Misusing and and or: Be clear about your logic. and requires all conditions to be True, while or only requires one.
Unnecessary if statements: You don’t need an ‘if’ statement to check a boolean variable. Instead of if is_knight == True:, you can simply write if is_knight:.

9.8 Conclusion and Further Resources

You’ve now mastered the art of ‘if’ statements, a crucial skill in your coding arsenal. With this power, your programs can now make decisions and respond to different conditions, just like a real knight on a quest.

To further hone your ‘if’ statement skills, check out these valuable resources:

Remember, every great Python sorcerer started where you are now. Keep practicing your ‘if’ statements, and soon you’ll be weaving complex decision-making logic into your code with ease. Onward to your next coding challenge!