Introduction to Python Programming

# 3.5Tuple basics

## Learning objectives

By the end of this section you should be able to

• Describe the features and benefits of a tuple.
• Develop a program that creates and uses a tuple successfully.
• Identify and discuss the mutability of a tuple.

## Creating tuples and accessing elements

A tuple is a sequence of comma separated values that can contain elements of different types. A tuple must be created with commas between values, and conventionally the sequence is surrounded by parentheses. Each element is accessed by index, starting with the first element at index 0.

 tuple_1 = (2, 3, 4) print(f'tuple_1: {tuple_1}') print(tuple_1[1]) print() data_13 = ('Aimee Perry', 96, [94, 100, 97, 93]) print(f'data_13: {data_13}') print(data_13[2])   tuple_1: (2, 3, 4) 3 data_13: ('Aimee Perry', 96, [94, 100, 97, 93]) [94, 100, 97, 93] 
Table 3.4 Example tuples.

## Concepts in Practice

### Creating tuples and accessing elements

1.
Consider the example above. Which accesses tuple_1's first element?
1. tuple_1[0]
2. tuple_1[1]
3. tuple_1[2]
2.
Which creates a valid tuple?
1. tuple_2 = (42, 26, 13)
2. tuple_3 = (42, 26, 13.5)
3. both
3.
Which creates a tuple with three elements?
1. my_tuple = 'a', 'b', 'c'
2. my_tuple = ['a', 'b', 'c']
3. my_tuple = ('a', 'b', 'c')

## Tuple properties

How do tuples compare to lists? Tuples are ordered and allow duplicates, like lists, but have different mutability. An immutable object cannot be modified after creation. A mutable object can be modified after creation. Tuples are immutable, whereas lists are mutable.

## Concepts in Practice

### Using tuples

4.
Consider the final program in the example above. What is the value of my_tuple?
1. (0.693, 0.414, 3.142)
2. (0.693, 1.414, 3.142)
3. Error
5.
Why does the following code produce an error?
tuple_1 = ('alpha', 'bravo', 'charlie')
tuple_1.append('charlie')

1. Append isn't allowed.
2. Duplicates aren't allowed.
3. Strings aren't allowed
6.
A programmer wants to create a sequence of constants for easy reference that can't be changed anywhere in the program. Which sequence would be the most appropriate?
1. list
2. tuple

## Mutability and performance

Tuples are immutable and have a fixed size, so tuples use less memory. Overall, tuples are faster to create and access, resulting in better performance that can be noticeable with large amounts of data.

## Try It

### Creating a tuple from a list

Suppose a programmer wants to create a tuple from a list to prevent future changes. The tuple() function creates a tuple from an object like a list. Ex: my_tuple = tuple(my_list) creates a tuple from the list my_list. Update the program below to create a tuple final_grades from the list grades.

## Try It

### Creating a tuple with user input

Write a program that reads in two strings and two integers from input and creates a tuple, my_data, with the four values.

Given input:

    x
y
15
20


The output is:

    my_data: ('x', 'y', 15, 20)


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