Course Content

Introduction to Python (copy)

1. Getting Started

First Steps Comments Simple Math: Add & Subtract Simple Math: Multiply & Divide Recap

2. Variables and Types

Data Types Storing Data in Variables Variable Naming Rules Using Variables String Indexing and Length String Slicing and Concatenation Challenge: Inventory Sorting Capstone Recap

3. Conditional Statements

Boolean Data Type Combining Conditions Challenge: Boolean Logic Membership Operators and Type Comparisons Conditional Expressions Challenge: Product Management Capstone Recap

4. Other Data Types

Lists and List Methods Nested Lists Challenge: List Management Tuples and Tuple Methods Tuple Operations Challenge: Tuple Operations Dictionaries and Dictionary Methods Challenge: Pricing Adjustment Capstone Recap

5. Loops

For Loops While Loops Range Function Iterating Over Indexes Challenge: Sales and Shipments Nested Loops Challenge: Automating Stock Control Challenge: Solo Coding Capstone Recap

6. Functions

Built-in Functions Challenge: Zip and Sort Functions User Defined Functions List Behavior in Functions Functions with no Return Modifying Functions Challenge: Product Revenues Capstone Recap

While Loops

while loops are the key tool for handling indefinite iteration, which is useful in scenarios where the number of iterations isn't known in advance, like monitoring inventory levels until they meet a specific threshold.

Watch as Alex demonstrates how to use while loops to handle dynamic situations:

A while loop in Python continuously runs a block of code as long as a specified condition remains True.

Syntax

To start a while loop, you define a counter variable and follow it with the while keyword and a boolean condition. The condition is followed by a colon :, which indicates the start of the loop's code block.

The loop will execute repeatedly until the condition becomes False. Typically, the counter variable is updated inside the loop to eventually make the condition False and stop the loop.

Take this while loop for example:


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# Handling a queue at a grocery store checkout
queue_length = 5  # Initial number of people in the queue
while queue_length > 0:  # Start the `while` loop as long as the queue isn't empty
    print(f"Current queue size: {queue_length}")
    
    # Simulate serving a customer
    print("Serving the next customer...")
    
    # Decrease the queue length by 1 as a customer leaves
    # The `-=` operator is a shortcut for `queue_length = queue_length - 1`
    queue_length -= 1

In this example, queue_length acts as our counter variable, starting at 5. With each loop iteration, the value of queue_length decreases by 1 until it reaches 0. At that point, the loop ends because the condition 0 > 0 evaluates to False.

Note

It is crucial to update the counter variable inside the loop to eventually meet the condition for stopping the loop. Without this, the loop will run infinitely, preventing any further code from executing.

Example Application

Imagine you're managing the milk stock in a grocery store. You need to ensure the stock doesn't drop below a certain level, and when it does, you should restock to maintain the stock level.

A while loop is useful in this situation because it allows you to restock milk in increments over several iterations until the stock reaches the desired level. Without a while loop, you'd need to calculate the exact amount of milk to restock all at once.

For instance, consider that a store worker can only restock a fixed amount of milk in one trip (e.g., 20 packs per restock). If the stock isn't fully replenished, the worker returns to the warehouse to bring another batch of milk.


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# Initial amount of milk in stock
milk_stock = 15
# Minimum stock level before restocking is necessary
min_stock = 50
# Quantity a worker can restock at one time
restock_quantity = 20

# Start the loop to restock milk until the stock exceeds the minimum required level
while milk_stock < min_stock:
    # If the loop is running, the condition is `True`, indicating we need more milk
    print(f"Milk stock is low: {milk_stock} units remaining.")
    # Simulate the process of restocking milk
    print("Restocking milk...")
    # Increase the stock by the quantity the worker can bring in one trip
    milk_stock += restock_quantity
    
# Output the final stock level after restocking is complete
print(f"Milk stock updated: {milk_stock} units, which is now sufficient.")

Note

milk_stock += restock_quantity is equivalent to milk_stock = milk_stock + restock_quantity. It's simply a more concise and readable way to express the same operation.

The flowchart above illustrates the logic behind the while loop used for managing the milk inventory. Notice how the counter variable milk_stock, starting at 15, is incremented by the restock_quantity with each loop iteration.

The loop keeps running until milk_stock surpasses the min_stock threshold of 50, at which point it stops.

Task

Swipe to start coding

Manage a grocery store’s inventory by using while loops to ensure that Bread, Eggs, and Apples meet their minimum stock levels. Restock quantities are stored in a dictionary.

Use a while loop to check if "Bread" is below its minimum stock. If so, increase its stock using the corresponding restock quantity from the dictionary.
Repeat the same logic for "Eggs" and "Apples", each with its own while loop.
After restocking, loop through the inventory dictionary using the for loop and print the final stock levels for all items.

Output Requirements

For each restocked item, print:
"<Item> stock is low: <$current_stock> units. Restocking..."
After all restocking, print Final Inventory after restocking: followed by the updated stock levels:
"<Item>: <$current_stock> units (Minimum required: <$minimum_stock> units)"
Insert a newline before the final inventory using \n.
Use f-strings for formatting and single quotes inside double-quoted strings for dictionary keys.

Note

To avoid syntax conflicts in f-strings, use double quotes around the string and single quotes inside: f"Bread stock is low: {inventory['Bread'][0]} units."
Use \n to start a new line in the output: "First line.\nSecond line."

Solution

Switch to desktop for real-world practiceContinue from where you are using one of the options below

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Section 5. Chapter 2

While Loops

Watch as Alex demonstrates how to use while loops to handle dynamic situations:

A while loop in Python continuously runs a block of code as long as a specified condition remains True.

Syntax

The loop will execute repeatedly until the condition becomes False. Typically, the counter variable is updated inside the loop to eventually make the condition False and stop the loop.

Take this while loop for example:


              1234567891011
            
# Handling a queue at a grocery store checkout
queue_length = 5  # Initial number of people in the queue
while queue_length > 0:  # Start the `while` loop as long as the queue isn't empty
    print(f"Current queue size: {queue_length}")
    
    # Simulate serving a customer
    print("Serving the next customer...")
    
    # Decrease the queue length by 1 as a customer leaves
    # The `-=` operator is a shortcut for `queue_length = queue_length - 1`
    queue_length -= 1

Note

It is crucial to update the counter variable inside the loop to eventually meet the condition for stopping the loop. Without this, the loop will run infinitely, preventing any further code from executing.

Example Application

Imagine you're managing the milk stock in a grocery store. You need to ensure the stock doesn't drop below a certain level, and when it does, you should restock to maintain the stock level.


              123456789101112131415161718
            
# Initial amount of milk in stock
milk_stock = 15
# Minimum stock level before restocking is necessary
min_stock = 50
# Quantity a worker can restock at one time
restock_quantity = 20

# Start the loop to restock milk until the stock exceeds the minimum required level
while milk_stock < min_stock:
    # If the loop is running, the condition is `True`, indicating we need more milk
    print(f"Milk stock is low: {milk_stock} units remaining.")
    # Simulate the process of restocking milk
    print("Restocking milk...")
    # Increase the stock by the quantity the worker can bring in one trip
    milk_stock += restock_quantity
    
# Output the final stock level after restocking is complete
print(f"Milk stock updated: {milk_stock} units, which is now sufficient.")

Note

milk_stock += restock_quantity is equivalent to milk_stock = milk_stock + restock_quantity. It's simply a more concise and readable way to express the same operation.

The loop keeps running until milk_stock surpasses the min_stock threshold of 50, at which point it stops.

Task

Swipe to start coding

Manage a grocery store’s inventory by using while loops to ensure that Bread, Eggs, and Apples meet their minimum stock levels. Restock quantities are stored in a dictionary.

Use a while loop to check if "Bread" is below its minimum stock. If so, increase its stock using the corresponding restock quantity from the dictionary.
Repeat the same logic for "Eggs" and "Apples", each with its own while loop.
After restocking, loop through the inventory dictionary using the for loop and print the final stock levels for all items.

Output Requirements

For each restocked item, print:
"<Item> stock is low: <$current_stock> units. Restocking..."
After all restocking, print Final Inventory after restocking: followed by the updated stock levels:
"<Item>: <$current_stock> units (Minimum required: <$minimum_stock> units)"
Insert a newline before the final inventory using \n.
Use f-strings for formatting and single quotes inside double-quoted strings for dictionary keys.

Note

To avoid syntax conflicts in f-strings, use double quotes around the string and single quotes inside: f"Bread stock is low: {inventory['Bread'][0]} units."
Use \n to start a new line in the output: "First line.\nSecond line."

Solution

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Section 5. Chapter 2

Switch to desktop for real-world practiceContinue from where you are using one of the options below