Day 3: 🙌 Coding Colab

Quick Reference

Here’s a quick reference for the basic control flow structures we’ll be using:

# If statement
if condition:
    # code to run if condition is True

# For loop
for item in sequence:
    # code to run for each item

# While loop
while condition:
    # code to run while condition is True

Here’s our course cheatsheet on control flows:

• Control Flows Cheatsheet

Feel free to refer to this cheatsheet throughout the exercise if you need a quick reminder about syntax or functionality.

Exercise Overview

In this Coding Colab, you’ll practice using basic control flow structures in Python. Work through these simple tasks with your partner, discussing your approach as you go.

Part 1: If Statements (20 minutes)

Task 1: Simple Weather Advice

Write a program that gives weather advice based on temperature:

1. Set a variable temperature = 20
2. Use an if-else statement to print advice:
   • If temperature is above 25, print “It’s a hot day, stay hydrated!”
   • Otherwise, print “Enjoy the pleasant weather!”

temperature = 20

# Your code here
# Use an if-else statement to print weather advice

Task 2: Grade Classifier

Create a program that assigns a letter grade based on a numerical score:

1. Set a variable score = 85
2. Use if-elif-else statements to print the letter grade:
   • 90 or above: “A”
   • 80-89: “B”
   • 70-79: “C”
   • 60-69: “D”
   • Below 60: “F”

score = 85

# Your code here
# Use if-elif-else statements to print the letter grade

Part 2: For Loops (20 minutes)

Task 3: Counting Sheep

Write a program that counts from 1 to 5, printing “sheep” after each number:

1. Use a for loop with the range() function
2. Print each number followed by “sheep”

# Your code here
# Use a for loop to count sheep

Task 4: Sum of Numbers

Calculate the sum of numbers from 1 to 10:

1. Create a variable total = 0
2. Use a for loop with the range() function to add each number to total
3. After the loop, print the total

total = 0

# Your code here
# Use a for loop to calculate the sum

Part 2.5: Two Ways to Think About the Same Problem (15 minutes)

Great job with those for loops! Now let’s connect what you just learned with the list comprehensions you practiced yesterday. You now know two different ways to solve the same problems - both are correct and useful in different situations.

Task 5: Counting Sheep - Both Ways

Let’s revisit the sheep counting problem and see how both approaches work:

# Method 1: Traditional for loop (what you just practiced)
print("Method 1 - Traditional Loop:")
for i in range(1, 6):
    print(f"{i} sheep")

print("\nMethod 2 - List Comprehension + Loop:")
# Method 2: List comprehension (what you learned yesterday) + loop
sheep_list = [f"{i} sheep" for i in range(1, 6)]
for sheep in sheep_list:
    print(sheep)

print("\nMethod 3 - List Comprehension Only:")
# Method 3: Just create the list and print it
sheep_list = [f"{i} sheep" for i in range(1, 6)]
print(sheep_list)

Method 1 - Traditional Loop:
1 sheep
2 sheep
3 sheep
4 sheep
5 sheep

Method 2 - List Comprehension + Loop:
1 sheep
2 sheep
3 sheep
4 sheep
5 sheep

Method 3 - List Comprehension Only:
['1 sheep', '2 sheep', '3 sheep', '4 sheep', '5 sheep']

Task 6: Sum of Numbers - Both Ways

Now let’s see different approaches to calculating sums:

# Method 1: Traditional loop with accumulator (what you just practiced)
total = 0
for i in range(1, 11):
    total += i
print(f"Method 1 - Traditional loop sum: {total}")

# Method 2: List comprehension + built-in sum function
numbers = [i for i in range(1, 11)]
total = sum(numbers)
print(f"Method 2 - Comprehension + sum(): {total}")

# Method 3: Even more concise (advanced Python)
total = sum(range(1, 11))
print(f"Method 3 - Built-in functions: {total}")

Method 1 - Traditional loop sum: 55
Method 2 - Comprehension + sum(): 55
Method 3 - Built-in functions: 55

Practice: Choose Your Approach

Now it’s your turn! Try solving this problem using both approaches:

Challenge: Create a list containing the squares of numbers 1 through 5

# Approach 1: Traditional loop
squares_traditional = []
# Your code here - use a for loop to add squares to the list

print("Traditional approach:", squares_traditional)

Traditional approach: []

# Approach 2: List comprehension
# Your code here - use a list comprehension to create squares

# print("Comprehension approach:", squares_comprehension)

Discussion Questions

With your partner, discuss:

1. Which approach felt more natural to you for each problem?
2. When might you prefer the traditional loop approach?
3. When might list comprehensions be better?
4. What are the advantages of knowing both approaches?

Key Takeaways

• Both approaches are correct - it depends on the situation and your preference
• Traditional loops are great when you need:
  • Complex logic or conditions
  • Step-by-step processing
  • To print or process items one at a time
• List comprehensions are excellent when you need to:
  • Transform data into a new list
  • Apply simple operations to sequences
  • Write more concise, readable code

You now have multiple tools in your Python toolkit! 🛠️

Part 3: While Loops (15 minutes)

Task 7: Countdown

Create a simple countdown program:

1. Set a variable countdown = 5
2. Use a while loop to print the countdown from 5 to 1
3. After each print, decrease the countdown by 1
4. When the countdown reaches 0, print “Blast off!”

countdown = 5

# Your code here
# Use a while loop for the countdown

Conclusion and Discussion (5 minutes)

With your partner, briefly discuss:

1. Which control structure (if, for, or while) did you find easiest to use?
2. Can you think of a real-life situation where you might use each of these control structures?

Remember, it’s okay if you don’t finish all tasks. The goal is to practice and understand these concepts. Good luck and enjoy coding together!