Tuple

Tuple is an ordered and immutable collection data structure. Ordered meaning it keeps the order of elements in which they are inserted, and immutable means that once the tuple is created it cannot change, and you cannot add or remove elements from it.

Lesson Overview

In this lesson we will cover:

• How to create tuple
• Accessing the elements in tuple
• Useful methods on tuples

Creating Tuple

A tuple is created by enclosing items in parentheses () separated by comma.

Python Sandbox

Tuples containing a single element still must contain a comma, otherwise python will read the wrong data type:

Python Sandbox

Accessing Elements

Accessing elements of the tuple is done with index, just like lists.

Python Sandbox

Useful methods

Unlike lists, as we cannot modify tuples, we don't have a lot of methods available to us, but we will list a few.

• count() - returns the number of times a specified value appears in tuple.
  Python Sandbox
• index() - returns index of the first occurrence of the element.
  Python Sandbox

📚Learn more about Python Tuples

Deep dive into Python tuples in this Deep Dive: tuples article by Real Python which takes you deep in topic of tuples and their usecases.

Exercise

Complete [TODO] Exercise 06 — WorkingTitle to practice tuples.

Assignment

Using lists to separatly hold multiple related values is brittle and will break if you do not pay attention to all lists containing data. In this assigment we will deal with those issues by using tuples.

1. Open our main.py file we have been working on
2. Create a new empty list called inventory. This will hold tuples of related data (product_name, product_price, product_stock).
3. Delete previusly defined item_name, item_price and item_stock variables, we wont need them anymore.
4. Just like before, in infinite loop, first check if the input is an empty string and if it is, break out of the loop, otherwise get the users input containing name, price and stock in a single line, then split the line using split() method to get a list of inputed data.
5. Instead of appending each data to their own list, create a tuple called item containing name, price and stock in that particular order and append that to our inventory list we declared earlier. Print out each inventory element using for loop.
6. On to customer ordering items now. Keep order list and instead of storing only totals for each item, we will now store item_name, item_quantity and line_total in tuple called line_item and append that to our order list so our shop can better keep track of the orders. Keep in mind - tuples are immutable which means that you will have to reduce stock of the item by replacing entire tuple with new stock value.
7. Same as before, calculate the total for all the items bought, apply a 10% discount if the total is over 100.
8. In the end, print out the inventory, to make sure that the items are actually removed once bought.
9. Make sure your program runs, then commit the changes and push to Github

What's Next

Now that you have seen data structures that can contain duplicates, it's time to meet set - a unique data structure that does not allows for duplicates.