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Lesson 3: Conditionals

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What are Conditionals?

Conditionals allow your program to make decisions.

Think of it like giving instructions to a robot:

If something is true, do one thing. Otherwise, do something else.

Real-Life Example

If it's raining, take an umbrella. Otherwise, don't.

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The Building Blocks

Python uses three keywords to make decisions:

• if
• elif
• else

Example

weather = "rainy"

if weather == "rainy":
    print("Take an umbrella")
elif weather == "sunny":
    print("Wear sunglasses")
else:
    print("Just go outside normally")

Output

Take an umbrella

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How It Works

Python checks each condition from top to bottom.

• if → Checks the first condition.
• elif → Checks another condition only if the previous one was False.
• else → Runs if none of the previous conditions were True.

Python stops checking as soon as it finds the first True condition.

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= vs ==

This is one of the most common beginner mistakes.

Symbol	Meaning
=	Assigns a value to a variable
==	Compares two values

Assignment (=)

age = 10

This stores the value 10 in the variable age.

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Comparison (==)

age = 10

print(age == 10)
print(age == 5)

Output

True
False

• age == 10 asks: "Is age equal to 10?"
• age == 5 asks: "Is age equal to 5?"

The answer is either True or False.

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Comparison Operators

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

Example

x = 10

print(x > 5)
print(x < 5)
print(x != 8)

Output

True
False
True

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Combining Conditions

Sometimes you need to check more than one condition.

Python provides three logical operators:

• and
• or
• not

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and

Both conditions must be True.

Example

age = 20
has_id = True

if age >= 18 and has_id:
    print("You can enter")
else:
    print("You cannot enter")

Output

You can enter

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or

At least one condition must be True.

Example

is_weekend = False
is_holiday = True

if is_weekend or is_holiday:
    print("No school today")

Output

No school today

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not

Reverses a Boolean value.

Example

is_logged_in = False

if not is_logged_in:
    print("Please log in")

Output

Please log in

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Practice Program

Create a file named lesson3.py and write the following code.

age = 15
has_permission = False

if age >= 18:
    print("You are an adult")
elif age >= 13 and age < 18:
    print("You are a teenager")
else:
    print("You are a kid")

if age >= 13 or has_permission:
    print("You can watch the movie")
else:
    print("Sorry, no movie for you")

Output

You are a teenager
You can watch the movie

Why?

• age is 15, so it is not greater than or equal to 18.
• It is greater than or equal to 13, so Python prints "You are a teenager."
• The second condition uses or.
• Since age >= 13 is already True, Python prints "You can watch the movie."
• It doesn't matter that has_permission is False because or only needs one condition to be True.

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Try It Yourself

Change the values:

age = 20
has_permission = True

What happens?

The output becomes:

You are an adult
You can watch the movie

Why?

• age >= 18 is now True, so Python prints "You are an adult."
• Both age >= 13 and has_permission are True, so the second message remains "You can watch the movie."

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Key Takeaways

• Conditionals allow programs to make decisions.
• if checks the first condition.
• elif checks another condition if the previous one was False.
• else runs when no conditions are True.
• = assigns a value, while == compares values.
• Use comparison operators to ask questions about values.
• and requires all conditions to be True.
• or requires at least one condition to be True.
• not reverses a Boolean value.

Back to the main roadmap | Previous lesson: Variables and Data Types | Next lesson: Type Casting

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Next Lesson: Type Casting