Tuples

Table of Contents

• Introduction
• Basic Tuple Operations
• Tuple Indexing and Slicing
• Tuple Methods

Introduction

Tuples are similar to lists with the difference that they are immutable. Once created, their elements cannot be changed unless a new tuple object is created. Tuples are the obvious choice for a collection of constants that never change throughout the program. It is written as a sequence of comma-separated values enclosed within a pair of parentheses ().

EXAMPLE Defining a tuple.

1tupA = (1,2,3,3,4,5,6)
2tupB = (1,2,3,"Python","code")
3print(tupA)
4print(tupB)

(1, 2, 3, 3, 4, 5, 6)
(1, 2, 3, 'Python', 'code')

A nested tuple is tuple that contains other tuples as its elements.

EXAMPLE Nested tuple.

1newTup = (tupA, tupB,(2,4,6))
2newTup

((1, 2, 3, 3, 4, 5, 6), (1, 2, 3, 'Python', 'code'), (2, 4, 6))

A tuple can also contain other data structures or types as its elements.

EXAMPLE Tuple can contain heterogeneous data.

1newTup1 = (tupA, [1,2,4],"string")
2newTup1

((1, 2, 3, 3, 4, 5, 6), [1, 2, 4], 'string')

Basic Tuple Operations

Just like lists, tuples can also be concatenated with the + operator.

EXAMPLE Concatenation of tuples.

1tupA + tupB

(1, 2, 3, 3, 4, 5, 6, 1, 2, 3, 'Python', 'code')

We can obtain the length (number of elements) of a tuple using the len() function.

EXAMPLE Length of a tuple.

1len(tupA)

7

A tuple can be repeated using the * operator.

EXAMPLE Repetition of a tuple.

1tupB*2

(1, 2, 3, 'Python', 'code', 1, 2, 3, 'Python', 'code')

The in keyword serves two purposes:

• used to check if a value is present in a sequence (e.g. list, tuple).
• used to iterate through a sequence in a for loop.

EXAMPLE Boolean expression with a tuple.

1"Python" in tupB # Is "Python" an element of tupB?

True

Tuple Indexing and Slicing

Just like lists, tuples are ordered which means their elements can be accessed by specifying their corresponding indices.

EXAMPLE Indexing of a tuple.

1tupA[1]

2

Due to its immutability, trying to modify a tuple will lead to an error.

EXAMPLE Tuple is immutable.

1tupA[1] = 20

---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

~\AppData\Local\Temp/ipykernel_6652/2988985137.py in <module>
----> 1 tupA[1] = 20


TypeError: 'tuple' object does not support item assignment

Instead, create a new tuple object by using a new assignment statement.

1tupA = (1,20,3,3,4,5,6)
2tupA

(1, 20, 3, 3, 4, 5, 6)

EXAMPLE Modifying a tuple using a list.

1temp = list(tupA)
2temp[1]=20
3tupA_updated = tuple(temp)
4tupA_updated

(1, 20, 3, 3, 4, 5, 6)

Slicing for tuples are similar to those for lists. Recall the slicing syntax:

sequence[start:stop:step]

Python uses half-open intervals: the start index is included while the stop index is not.

EXAMPLE Indexing of a tuple.

1tup1 = (2,4,6,8,9,10)
2tup1[0]

2

EXAMPLE Negative indexing.

1tup1[-2]

9

EXAMPLE Slicing of a tuple.

1tup1[2:]

(6, 8, 9, 10)

Chain indexing and slicing work for a nested tuple.

EXAMPLE Indexing of a nested tuple.

1tupA = (1,2,3,3,4,5,6)
2newTup1 = (tupA, [1,2,4],"string")
3newTup1[0]

(1, 2, 3, 3, 4, 5, 6)

EXAMPLE Chain indexing and slicing of a nested tuple.

1newTup1[0][2:5]

(3, 3, 4)

ADVERTISEMENT

Tuple Methods

The count() method returns the number of elements with the specified value.

EXAMPLE count() method.

1numbers = (1,2,2,2,3,3,4,5,6,6,8)
2numbers.count(3) # counts how many times the number 3 appears

2

The index() method searches the tuple for a specified value and returns its index.

EXAMPLE index() method.

1numbers.index(5)

7

In cases where there is more than one occurrence of the specified value, the index() method will only return the first index.

EXAMPLE index() method.

1numbers.index(2)

1

In contrast to lists, we see that there are fewer methods available to tuples since they are immutable.