Sometimes we can have more than two possible scenarios which need a different code to be ran. We can add elif statements to allow for as many outcomes as we want.
In Python, elif is short for else if.
language = "Python"
if language == "JavaScript":
print("It's super popular!")
elif language == 'Python':
print("It's so simple!")
elif language == 'Java':
print("It's pretty hardcore!")
else:
print("It's exotic!")
In the example above, language == "JavaScript" evaluates to false, so we move on and enter the following elif.
There, language == "Python" evaluates to true, so we execute what's inside that block and print "It's so simple!".
The rest of the conditions are not evaluated.
In case none of the conditions evaluates to true, then the code in the final else statement would execute. For example, if language was "Go", the program would have printed "It's exotic!"
Assignment
Follow the Coding Tutorial and let's write some chained conditionals.
Hint
Look at the examples above if you get stuck.
In this lesson, we will explore the concept of chaining conditionals in Python using the if, elif, and else statements. This is a fundamental concept in programming that allows us to handle multiple conditions and execute different blocks of code based on those conditions. Chaining conditionals is particularly useful in scenarios where we need to make decisions based on various criteria, such as user input, sensor data, or any other dynamic data.
Before diving into more complex examples, let's understand the basic syntax and usage of if, elif, and else statements. The if statement is used to test a condition, and if the condition is true, the code block inside the if statement is executed. The elif (short for "else if") statement allows us to check multiple conditions. If the condition for if is false, it checks the condition for the elif block. If the elif condition is true, its code block is executed. The else statement is optional and is executed if none of the preceding conditions are true.
temperature = 25
if temperature > 30:
print("It's a hot day!")
elif temperature > 20:
print("It's a warm day!")
else:
print("It's a cool day!")
In this example, the variable temperature is checked against multiple conditions. If the temperature is greater than 30, it prints "It's a hot day!". If the temperature is not greater than 30 but greater than 20, it prints "It's a warm day!". If neither condition is true, it prints "It's a cool day!".
Let's delve deeper into the key concepts and techniques involved in chaining conditionals.
The logical flow of chained conditionals is straightforward. The program evaluates each condition in sequence. As soon as it finds a true condition, it executes the corresponding code block and skips the rest of the conditions. If none of the conditions are true, it executes the else block (if present).
We can also nest conditionals within each other to handle more complex scenarios. However, it's important to keep the code readable and maintainable.
We can combine multiple conditions using logical operators like and, or, and not to create more complex conditional statements.
Let's look at some examples to understand how chaining conditionals can be applied in various contexts.
score = 85
if score >= 90:
print("Grade: A")
elif score >= 80:
print("Grade: B")
elif score >= 70:
print("Grade: C")
elif score >= 60:
print("Grade: D")
else:
print("Grade: F")
In this example, the program assigns a grade based on the score. It checks the score against multiple conditions and prints the corresponding grade.
light_color = "Red"
if light_color == "Green":
print("Go")
elif light_color == "Yellow":
print("Slow down")
elif light_color == "Red":
print("Stop")
else:
print("Invalid color")
This example simulates a traffic light system where the program prints an action based on the color of the traffic light.
When working with chained conditionals, it's important to be aware of common mistakes and follow best practices to write clear and efficient code.
elif and using multiple if statements instead, which can lead to redundant checks.Once you are comfortable with basic chaining conditionals, you can explore advanced techniques such as:
Encapsulate conditional logic within functions to make the code more modular and reusable.
Use dictionaries to map conditions to actions, which can make the code cleaner and more efficient.
Let's implement a more complex example that demonstrates the use of chaining conditionals in a real-world scenario.
def get_discount(category, is_member):
if category == "Electronics":
if is_member:
return 0.10 # 10% discount for members
else:
return 0.05 # 5% discount for non-members
elif category == "Clothing":
if is_member:
return 0.15 # 15% discount for members
else:
return 0.10 # 10% discount for non-members
elif category == "Groceries":
if is_member:
return 0.05 # 5% discount for members
else:
return 0.02 # 2% discount for non-members
else:
return 0.00 # No discount for other categories
# Example usage
category = "Electronics"
is_member = True
discount = get_discount(category, is_member)
print(f"Discount for {category} (Member: {is_member}): {discount * 100}%")
In this example, the get_discount function calculates the discount based on the product category and membership status. It uses nested conditionals to handle different scenarios.
Debugging and testing are crucial aspects of writing reliable code. Here are some tips for debugging and testing chained conditionals:
unittest or pytest to automate the testing process.import unittest
class TestDiscounts(unittest.TestCase):
def test_electronics_member(self):
self.assertEqual(get_discount("Electronics", True), 0.10)
def test_electronics_non_member(self):
self.assertEqual(get_discount("Electronics", False), 0.05)
def test_clothing_member(self):
self.assertEqual(get_discount("Clothing", True), 0.15)
def test_clothing_non_member(self):
self.assertEqual(get_discount("Clothing", False), 0.10)
def test_groceries_member(self):
self.assertEqual(get_discount("Groceries", True), 0.05)
def test_groceries_non_member(self):
self.assertEqual(get_discount("Groceries", False), 0.02)
def test_other_category(self):
self.assertEqual(get_discount("Toys", True), 0.00)
if __name__ == '__main__':
unittest.main()
When approaching problems related to chaining conditionals, consider the following strategies:
In this lesson, we covered the concept of chaining conditionals in Python using if, elif, and else statements. We explored the basics, main concepts, examples, common pitfalls, best practices, advanced techniques, and debugging and testing tips. Mastering chaining conditionals is essential for writing robust and efficient code. Keep practicing and exploring further applications to enhance your programming skills.
Here are some additional resources to help you learn more about chaining conditionals and related topics: