Business is full of rules and decisions. “If a customer spends over $100, they get a 10% discount.” “If inventory is below 50 units, flag it for reorder.” In Python, we implement this decision-making process using conditional statements.
if: Executes a block of code only if a certain condition is True.else: Provides an alternative block of code to execute if the if condition is False.elif (“else if”): Lets you check for multiple, sequential conditions. Python executes the first block where the condition is True and then skips the rest.# Classifying a customer based on their total spending
if total_spent > 1000:
customer_tier = "Gold"
elif total_spent > 500:
customer_tier = "Silver"
else:
customer_tier = "Standard"
Before you begin, ensure you have followed the setup instructions in the main README.md to set up your virtual environment and install the required libraries.
The script for this lesson, conditionals.py, has been refactored to encapsulate each business rule into a separate, testable function.
Day_09_Conditionals/conditionals.py. Notice the functions calculate_discount_percent(), calculate_shipping_cost(), and calculate_employee_bonus().Coding-For-MBA), run the script to see the functions in action:
python Day_09_Conditionals/conditionals.py
pytest tests/test_day_09.py
Discount Policy Automation:
my_solutions_09.py), import the calculate_discount_percent function.purchase_amount variable.purchase_amount * (1 - discount_rate)).120, 75, and 40.Shipping Cost Calculator:
calculate_shipping_cost function."USA", "Canada", "Mexico") and weights (40, 60) to see the results. Print a user-friendly message for each case.Employee Bonus Calculation:
calculate_employee_bonus function.performance_rating of 5.performance_rating of 4.🎉 Fantastic progress! You can now translate complex business rules into code that makes decisions automatically. This is a fundamental skill for automating reports and building analytical models.
Run this lesson’s code interactively in your browser:
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???+ example “conditionals.py” View on GitHub
```python title="conditionals.py"
"""
Day 9: Implementing Business Logic with Conditionals (Refactored)
This script demonstrates how to use if, elif, and else statements
to create business rules and make decisions in code. This version is
refactored into functions for better organization and testability.
"""
def calculate_discount_percent(purchase_amount):
"""Calculates a discount percentage based on the purchase amount."""
if not isinstance(purchase_amount, (int, float)) or purchase_amount < 0:
return 0.0
if purchase_amount > 100.00:
return 0.10 # 10% discount
elif purchase_amount > 50.00:
return 0.05 # 5% discount
else:
return 0.00 # 0% discount
def calculate_shipping_cost(country, order_weight_kg):
"""Calculates shipping cost based on destination and weight."""
if country == "USA":
if order_weight_kg > 50:
return 75
else:
return 50
elif country == "Canada":
if order_weight_kg > 50:
return 100
else:
return 65
else:
return -1 # Using -1 to indicate not available
def calculate_employee_bonus(performance_rating, department, salary):
"""Calculates an employee's bonus based on performance and department."""
if performance_rating >= 4:
if department == "Sales":
return salary * 0.15
else:
return salary * 0.10
elif performance_rating == 3:
return salary * 0.05
else:
return 0.0
if __name__ == "__main__":
# --- Example 1: Customer Discount Policy ---
print("--- Customer Discount Calculator ---")
customer_purchase = 125.50
discount_rate = calculate_discount_percent(customer_purchase)
discount = customer_purchase * discount_rate
final = customer_purchase - discount
print(f"Original Price: ${customer_purchase:.2f}")
print(f"Discount ({discount_rate * 100}%): ${discount:.2f}")
print(f"Final Price: ${final:.2f}")
print("-" * 20)
# --- Example 2: Nested Conditionals for Shipping Costs ---
print("--- Shipping Cost Calculator ---")
shipping_country = "Canada"
weight = 60
cost = calculate_shipping_cost(shipping_country, weight)
if cost != -1:
print(f"Shipping to {shipping_country} for a {weight}kg package costs: ${cost}")
else:
print(f"Sorry, shipping to {shipping_country} is not available.")
print("-" * 20)
# --- Example 3: Complex Bonus Calculation ---
print("--- Employee Bonus Calculator ---")
emp_rating = 5
emp_dept = "Sales"
emp_salary = 80000
bonus_amount = calculate_employee_bonus(emp_rating, emp_dept, emp_salary)
print(
f"Employee in {emp_dept} with rating {emp_rating} gets a bonus of: ${bonus_amount:.2f}"
)
print("-" * 20)
```
???+ example “solutions.py” View on GitHub
```python title="solutions.py"
"""
Day 9: Solutions to Exercises
"""
# --- Exercise 1: Discount Policy Automation ---
print("--- Solution to Exercise 1 ---")
purchase_amount = 120
if purchase_amount > 100:
discount = 0.10
elif purchase_amount > 50:
discount = 0.05
else:
discount = 0.0
final_price = purchase_amount * (1 - discount)
print(f"Original Amount: ${purchase_amount:.2f}")
print(f"Discount Rate: {discount * 100}%")
print(f"Final Price: ${final_price:.2f}")
print("-" * 20)
# --- Exercise 2: Shipping Cost Calculator ---
print("--- Solution to Exercise 2 ---")
# We can wrap this in a function to easily test different scenarios
def get_shipping_cost(country, order_weight_kg):
cost = 0
if country == "USA":
if order_weight_kg > 50:
cost = 75
else:
cost = 50
elif country == "Canada":
if order_weight_kg > 50:
cost = 100
else:
cost = 65
else:
return "Shipping not available."
return f"Shipping cost: ${cost}"
# Test cases
print(f"USA, 60kg -> {get_shipping_cost('USA', 60)}")
print(f"Canada, 40kg -> {get_shipping_cost('Canada', 40)}")
print(f"Mexico, 30kg -> {get_shipping_cost('Mexico', 30)}")
print("-" * 20)
# --- Exercise 3: Employee Bonus Calculation ---
print("--- Solution to Exercise 3 ---")
def calculate_bonus(rating, department, salary):
bonus_rate = 0
if rating >= 4:
if department == "Sales":
bonus_rate = 0.15
else:
bonus_rate = 0.10
elif rating == 3:
bonus_rate = 0.05
# No need for an else for rating 1 or 2, as bonus_rate is already 0
bonus_amount = salary * bonus_rate
return bonus_amount
# Test cases
salary = 90000
print(
f"Sales employee with rating 5 gets bonus: ${calculate_bonus(5, 'Sales', salary):,.2f}"
)
print(
f"Engineering employee with rating 4 gets bonus: ${calculate_bonus(4, 'Engineering', salary):,.2f}"
)
print(
f"Sales employee with rating 3 gets bonus: ${calculate_bonus(3, 'Sales', salary):,.2f}"
)
print(f"HR employee with rating 2 gets bonus: ${calculate_bonus(2, 'HR', salary):,.2f}")
print("-" * 20)
```