Learn Nested Loops

Nested loops extend the power of simple loops by allowing you to perform repeated actions across multiple dimensions. This is crucial for handling more complex tasks in a grocery store environment, such as organizing multi-layered inventory data or coordinating schedules across different departments.

Watch as Alex showcases how nested loops can be utilized to enhance efficiency and manage complex scenarios in our grocery store setting:

Here is the basic structure of a nested for loop in Python:

for outer_var in outer_sequence:
    for inner_var in inner_sequence:
        # Code to run for each combination

This means that for every value in the outer sequence, the inner loop will run through its entire sequence.

Nested loops are incredibly useful in programming when you need to loop through multiple sequences at the same time. By placing one loop inside another, you can iterate over elements in two or more dimensions, such as a list of lists:


              123456789
            
# Simple list of lists: each sublist is a department
items = [
    ["Apple", "Banana"],  # Fruits
    ["Milk", "Cheese"]    # Dairy
]

for department in items:
    for item in department:
        print(item)

The outer loop goes through each sublist in department_stocks, with each sublist standing for a department. The inner loop prints every item in the current sublist. The outer loop moves to the next department only after all items in the current sublist have been printed.

What If You didn't Use a Nested Loop

If you try to print every item in a list of lists without using a nested loop, you might accidentally print the sublists themselves, not the items inside them. Here is what the code would look like with only a single loop:

items = [
    ["Apple", "Banana"],  # Fruits
    ["Milk", "Cheese"]    # Dairy
]

for department in items:
    print(department)

This code prints:

['Apple', 'Banana']
['Milk', 'Cheese']

Instead of printing each grocery item, you get the entire sublist (department) as a single line.

Note

Without a nested loop, you cannot access each item inside the inner lists directly. Nested loops are necessary when you need to work with elements inside multiple layers of a data structure.


              123456789
            
# List of lists representing grocery sections
items = [
    ["Apple", "Banana"],  # Fruits
    ["Milk", "Cheese"]    # Dairy
]

# Non-nested loop: prints each sublist as a whole
for section in items:
    print(section)

Task

Swipe to start coding

You are given two lists of grocery items: produce and dairy.

First, combine these two lists into one list called groceries. Each list (produce and dairy) should be an element inside groceries.

Then use nested for loops to print all item names:

The outer loop goes through each list inside groceries (call it section).
The inner loop goes through each item inside that list.
Print each item on a new line in this format: Item name: <item>

Solution

Everything was clear?

Thanks for your feedback!

Section 5. Chapter 8

single

Ask AI

Ask anything or try one of the suggested questions to begin our chat

Swipe to show menu