Learn For Loops with Different Structures

Let's explore using for loop with different data structures.

for loops in Python can be used with any iterable object (lists, tuples, dictionaries, strings), allowing for data manipulation on a per-element basis.

Whether you need to access items in a list, keys or values in a dictionary, or characters in a string, for loops provide a clear syntax that simplifies code for repetitive tasks.

Here's how you can use a for loop to iterate over the elements in a string and a tuple, similar to how we saw with lists:


              123456789
            
# Print each letter in the string
vegetable = "Carrot"
for letter in vegetable:
    print(letter)

# Tuple containing different categories of the grocery store
categories = ("Produce", "Bakery", "Meat", "Dairy")
for category in categories:
    print(category)

In the example above, you loop through each letter in the string and each item in the tuple, printing them one by one. This demonstrates how for loops can process every element in different types of sequences, making your code both efficient and easy to read.

When using a for loop with a dictionary, iterating directly over the dictionary will loop through its keys by default.

Here's what to expect when you directly iterate over a dictionary:


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# Dictionary of products and their stock counts
productStock = {"milk": 120, "eggs": 200, "bread": 80}

# Print each dictionary key
print("Product list:")
for product in productStock:
    print(product)

Notice how the iterator variable product only accesses the dictionary keys.

To iterate over the values of a dictionary, you can use the values() method.

This is useful for operations that require access to values without needing to reference the keys:


              1234567
            
# Dictionary of products and their stock counts
productStock = {"milk": 120, "eggs": 200, "bread": 80}

# Print each dictionary value
print("Stock counts:")
for stock in productStock.values():
    print(stock)

If you need to access the keys and values simultaneously, the items() method allows you to loop through key-value pairs in a dictionary.

To use this method in a for loop, we specify two variables before the in keyword — one for the key (product) and one for the value (stock):


              1234567
            
# Dictionary of products and their stock counts
productStock = {"milk": 120, "eggs": 200, "bread": 80}

# Print both the key and value for each dictionary item
print("Inventory details:")
for product, stock in productStock.items():
    print(f"{product} has {stock} units in stock.")

Note

In this example, we use f-strings (also known as formatted string literals) to embed variables directly into strings. The syntax is simple: add an f before the opening quotation mark ", and place variables or expressions inside curly braces {} within the string. This method makes combining strings and variables in print statements much more readable, so it's worth learning.

Drawing on your knowledge of if/else, boolean operators, and for loops, we can run a simple inventory check on a dictionary:


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# Product names as keys and their stock levels as values
inventory = {
    "milk": 120,
    "eggs": 30,
    "bread": 80,
    "apples": 10
}

# The threshold stock level that triggers a restock
minimum_stock = 50

# Evaluating stock levels and deciding if restocking is necessary
print("Checking inventory status:")
for product, quantity in inventory.items():
    if quantity < minimum_stock:
        print(f"{product} requires restocking. Only {quantity} units remain.")
    else:
        print(f"{product} has adequate stock with {quantity} units available.")

Note

You may notice that we've placed if statements inside the for loop, which added extra indentation to the if block. As mentioned earlier, each indented block of code can be treated as independent, regardless of where it's placed. The key is to ensure that the indentation is consistent and correct between them.

Task

Swipe to start coding

Loop through a dictionary of grocery items and their prices. For each item:

Use a for loop to iterate through the grocery dictionary;
Print both the item (key) and its price (value) inside the loop.

Solution

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Section 5. Chapter 2

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Let's explore using for loop with different data structures.

for loops in Python can be used with any iterable object (lists, tuples, dictionaries, strings), allowing for data manipulation on a per-element basis.

Whether you need to access items in a list, keys or values in a dictionary, or characters in a string, for loops provide a clear syntax that simplifies code for repetitive tasks.

Here's how you can use a for loop to iterate over the elements in a string and a tuple, similar to how we saw with lists:


              123456789
            
# Print each letter in the string
vegetable = "Carrot"
for letter in vegetable:
    print(letter)

# Tuple containing different categories of the grocery store
categories = ("Produce", "Bakery", "Meat", "Dairy")
for category in categories:
    print(category)

When using a for loop with a dictionary, iterating directly over the dictionary will loop through its keys by default.

Here's what to expect when you directly iterate over a dictionary:


              1234567
            
# Dictionary of products and their stock counts
productStock = {"milk": 120, "eggs": 200, "bread": 80}

# Print each dictionary key
print("Product list:")
for product in productStock:
    print(product)

Notice how the iterator variable product only accesses the dictionary keys.

To iterate over the values of a dictionary, you can use the values() method.

This is useful for operations that require access to values without needing to reference the keys:


              1234567
            
# Dictionary of products and their stock counts
productStock = {"milk": 120, "eggs": 200, "bread": 80}

# Print each dictionary value
print("Stock counts:")
for stock in productStock.values():
    print(stock)

If you need to access the keys and values simultaneously, the items() method allows you to loop through key-value pairs in a dictionary.

To use this method in a for loop, we specify two variables before the in keyword — one for the key (product) and one for the value (stock):


              1234567
            
# Dictionary of products and their stock counts
productStock = {"milk": 120, "eggs": 200, "bread": 80}

# Print both the key and value for each dictionary item
print("Inventory details:")
for product, stock in productStock.items():
    print(f"{product} has {stock} units in stock.")

Note

Drawing on your knowledge of if/else, boolean operators, and for loops, we can run a simple inventory check on a dictionary:


              123456789101112131415161718
            
# Product names as keys and their stock levels as values
inventory = {
    "milk": 120,
    "eggs": 30,
    "bread": 80,
    "apples": 10
}

# The threshold stock level that triggers a restock
minimum_stock = 50

# Evaluating stock levels and deciding if restocking is necessary
print("Checking inventory status:")
for product, quantity in inventory.items():
    if quantity < minimum_stock:
        print(f"{product} requires restocking. Only {quantity} units remain.")
    else:
        print(f"{product} has adequate stock with {quantity} units available.")

Note

Task

Swipe to start coding

Loop through a dictionary of grocery items and their prices. For each item:

Use a for loop to iterate through the grocery dictionary;
Print both the item (key) and its price (value) inside the loop.

Solution

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Everything was clear?

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Section 5. Chapter 2

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