9. Compound Conditions

Compound conditions allow programs to evaluate multiple criteria at the same time. By combining conditions with Logical Operators, you can write clearer and more powerful decision-making logic.

These structures are essential for handling complex, real-world scenarios. They enable your program's computational logic to manage decisions that depend on several requirements simultaneously, providing flexibility and precision.

1. Compound Logic and Boolean Evaluation

1.1 The and Operator

Use and when all conditions must be True for the whole expression to be True.

flowchart LR
    A[Condition 1] --> B{and}
    C[Condition 2] --> B
    B --> D[True only if both are True]

Example:

age = 20
has_ticket = True

if age >= 18 and has_ticket:
    print("Access granted")

1.2 The or Operator

Use or when at least one of the conditions must be True for the whole expression to be True.

flowchart LR
    A[Condition 1] --> B{or}
    C[Condition 2] --> B
    B --> D[True if any is True]

Example:

country = "Canada"

if country == "USA" or country == "Canada":
    print("Eligible region")

1.3 The not Operator

Use not to invert a condition.

• not True becomes False
• not False becomes True

flowchart LR
    A[Condition] --> B{not}
    B --> C[Inverted Result]

Example:

has_id = False

if not has_id:
    print("ID required")

2. Python Shorts (Video)

A Python Shorts video demonstrating how to combine conditions using and, or.

If the video doesn't load, open directly on YouTube: Watch Python Shorts: Compound Conditions (and, or) ↗

3. Commented Examples

3.1. Using and for Simultaneous Requirements

# 1. Setup: Define an integer variable (int)
num = 25

# 2. Decision: Check if number is between 20 and 30 (both conditions must be True)
if num >= 20 and num <= 30:
    # 3. Output: Executes only if both conditions are True
    print("Number between 20 and 30")

Explanation:

• Compound conditions combine multiple comparisons using and or or.
• The and operator executes the block only if both conditions are True.
• Python evaluates from left to right and stops if one condition is False.
• This allows multiple requirements to be checked in a single if statement.

3.2. Using or for Alternative Requirements

# 1. Setup: Define an integer variable (int)
stock = 0
# 2. Setup: Define an boolean variable (bool)
has_priority_order = True

# 3 Decision: Check if stock is empty or there is a priority order
if stock == 0 or has_priority_order:
    # 4. Output: Executes if at least one condition is True
    print("Order can be processed")

Explanation:

• The or operator executes the block if at least one condition is True.
• Python evaluates conditions from left to right and stops if one is True (short-circuit).
• This allows alternatives to satisfy a single requirement.

3.3. Using not for Logical Inversion

# 1. Setup: Define a boolean variable (bool)
is_online = False

# 2. Decision: Check if user is not online
if not is_online:
    # 3. Output: Executes when the condition is True
    print("User is offline")

Explanation:

• The not operator reverses a Boolean value.
• not False becomes True, and not True becomes False.
• This allows checking the opposite of a condition in a single statement.

4. Short Practice Exercises

4.1. Multiple Requirements (and)

What will the following code print if average = 92 and absences = 0?

if average > 90 and absences == 0:
    print("Eligible")

Show solution

"Eligible"

Explanation: and requires both conditions to be True. Since 92 > 90 is True and 0 == 0 is True, the combined expression is True.

4.2. Alternative Requirements (or)

Consider the code below. If senior_citizen = False and purchase_total = 1200, will the message "Discount Applied" be printed?

if senior_citizen or purchase_total > 1000:
    print("Discount Applied")

Show solution

Yes

Explanation: or is True if at least one condition is met; since 1200 > 1000 is True, the entire expression passes.

4.3. Range Validation (and)

Does the following condition correctly evaluate whether month is between 1 and 12?

month >= 1 and month <= 12

Show solution

Yes

Explanation: and requires both conditions (month >= 1 and month <= 12) to be True to validate the month is within the inclusive range.

4.4. Logical Evaluation

Determine the result of:

(100 < 50) or (7 == 7)

Show solution

True

Explanation: or is True if at least one condition is True; since 7 == 7, the whole expression is True.

5. Google Colab: Try It Yourself

Practice compound conditions with this interactive Colab notebook:

👉 Open the Compound Conditions Colab notebook ↗

First time using Google Colab? Read the quick beginner guide ↗

6. Mini-Quiz

6.1. What is a compound condition?

A) A statement that tests one condition only.
B) A condition that includes a loop.
C) A statement combining two or more conditions.
D) A condition that always returns True.

Show answer

C) A statement combining two or more conditions.

6.2. Which logical operator returns True only if both conditions are True?

A) or
B) not
C) and
D) if

Show answer

C) and

6.3. What is the result of the expression (5 > 3) and (2 < 1)?

A) True
B) False
C) None
D) Error

Show answer

B) False

6.4. Which condition checks if num is between 10 and 50 (inclusive)?

A) num > 10 or num < 50
B) num >= 10 and num <= 50
C) num <= 10 or num >= 50
D) num == 10 and num == 50

Show answer

B) num >= 10 and num <= 50

6.5. Which operator returns True if at least one condition is True?

A) and
B) or
C) not
D) elif

Show answer

B) or

7. Common Mistakes

• Mixing up and and or when checking ranges.
• Using or when checking a value inside a range.
• Misusing not and unintentionally reversing logic.
• Forgetting relational operators inside compound conditions.

8. Summary Diagram

mindmap
  root((Compound Conditions))
    Logical Operators
      and - all conditions True
      or - at least one True
      not - logical inversion
    Common Uses
      Range checks
      Multiple requirements
      Alternative conditions
    Key Points
      Boolean evaluation
      Clear logical structure

9. Optional Extensions

• Write a program that asks for age and membership status and determines discount eligibility using and and or.
• Extend Example 3.1 so that it also prints "Out of range" when the number is below 20 or above 30.
• Research how Python evaluates compound conditions using short-circuit evaluation and test it with print statements.