02 CDT - 05 Tuples

A tuple is similar to a list in that it contains a collection of elements, which can be of different types.

However, unlike lists, tuples are immutable, meaning that once a tuple is created, its elements cannot be modified. This makes tuples read-only sequences. So the methods to update the list like append, extend, insert, remove, pop, clear do not work.

Tuple is meant for storing data which should not be modified and to retrieve data on demand.

• Elements in a tuple are separated by commas and enclosed in parentheses ().

>>> tup = ()
>>> tup
()

>>> tup = 1,2,3,4
>>> tup
(1, 2, 3, 4)

>>> tpl = (1, 2, 3, "apple", 4.5)
>>> tpl
(1, 2, 3, 'apple', 4.5)

A single element needs a , to be considered a tuple

>>> tup = (10,)
>>> tup
(10,)
>>> type(tup)
<class 'tuple'>

>>> tup = (10)
>>> tup
10
>>> type(tup)
<class 'int'>

Key Characteristics of Tuples:

1. Immutable: Once a tuple is created, you cannot change its elements. This makes it a read-only sequence.

• tpl[0] = 10 trying to modify element will raise an error.

2. Heterogeneous Elements: A tuple can contain elements of different types, just like a list.

>>> tpl = (23, "Kamal", [2, 3, 5, 7])

3. Accessing Elements: Values can be accessed and extracted from a tuple using indexing (with square brackets) or slicing, similar to list.

>>> tpl = (1, 2, 3, "apple", 4.5)
>>> tpl[1]
2
>>> tpl[-2]
'apple'

4. Slicing: Just like lists, tuples support slicing to extract parts of the tuple.

>>> tpl = (1, 2, 3, "apple", 4.5)
>>> tpl[1:3]
(2, 3)

>>> tpl[-2:]
('apple', 4.5)

>>> tpl[-1:]
(4.5,)

5. Multiplying Tuples: Tuples can be repeated using the multiplication operator *.

>>> tpl*2
(1, 2, 3, 'apple', 4.5, 1, 2, 3, 'apple', 4.5)

6. Simultaneous Assignment: Tuples are often used in Python for simultaneous assignment, where multiple variables can be assigned values from a tuple in a single statement.

This is very similar to using a list, but tuples are typically used when the values should remain constant.

>>> tup = (23, 'Kamal', [2,3,5,7])

>>> age, name, primes = tup

>>> age
23
>>> name
'Kamal'
>>> primes
[2, 3, 5, 7]

>>> age, name, primes
(23, 'Kamal', [2, 3, 5, 7])

7. Converting a list and range into a tuple

>>> lst = [1,2,3,4]
>>> tuple(lst)
(1, 2, 3, 4)

>>> tuple(range(4,9,2))
(4, 6, 8)

Use Cases for Tuples:

• Data Integrity: Use tuples when you want to ensure that the data remains unchanged, as tuples cannot be modified once created.
• Multiple Return Values: Functions often use tuples to return multiple values.

def get_coordinates():
  return (3.5, 4.8)

x, y = get_coordinates()

• Performance: Since tuples are immutable, they are generally faster than lists for iteration and storage.

Tuple of Values: assigning a tuple of values to a variable, is useful for grouping related data.

>>> point = (3.5, 4.8)
>>> point
(3.5, 4.8)

>>> date = 16, 'Jan', 2023
>>> date
(16, 'Jan', 2023)

>>> xcoordinate = point[0] # 3.5
>>> monthyear = date[1:]   # (7, 2023)

Methods for tuples

repeated using * Concatenation using + in and not in membership operators

len()
min()
max() count() index() sorted() sorted( tple, reverse=True)

To accept a tuple and display their sum and average

>>> num = eval( input("Enter elements in (): ") )
Enter elements in (): (1,2,3,4,5,6)
>>> sum = 0
>>> n = len(num)
>>> for i in range(n):
...     sum += num[i]
... 
>>> sum
21
>>> sum/n   # average
3.5

A program to find the first occurrence of an element in a tuple

>>> str = input( 'Enter comma separated elements: ').split(',')
Enter comma separated elements: 10,20,30,40

>>> tup = tuple(str)

>>> str = input( 'Enter comma separated elements: ').split(',')
Enter comma separated elements: 10,20,30,40

>>> lst = [int(s) for s in str]

>>> tup = tuple(lst)

>>> ele = int( input("Enter an element to search: "))
Enter an element to search: 20

>>> try:
...     pos = tup.index(ele)
...     print('Element was in position', pos+1)
>>> exceptValueError:  # error if not found
...     print('Element not found in tuple')


>>> str
['10', '20', '30', '40']
>>> tup
('10', '20', '30', '40')
>>> lst
[10, 20, 30, 40]
>>> tup
(10, 20, 30, 40)