COL100 �Introduction to Computer Science

Lecture 18 – Tuples

February, 2025

Semester II

2024-2025

Vireshwar Kumar, Aaditeshwar Seth

CSE@IITD

Agenda

• Tuple examples

2

Disclaimer: The contents of these slides are taken from various publicly available resources such as books, talks and lectures. They are being used for the purpose of classroom teaching and academic dissemination only. The sources are acknowledged wherever possible.

Tuple

• Can be used to store a collection of elements in a single variable

​

• Represented using round brackets

​

• Can have mixed element types

​

• Can have duplicate values

​

​

aTup = ("apple",5,"banana",3.2) print(aTup)

print(type(aTup))

print(len(aTup))

​

​

​

3

Indexing

• Tuple is an ordered sequence of elements.

​

• Each element can be accessed using its index.

​

• Backward indexing

​

• Multiple elements can be accessed using a range of indices
• [start : stop : step]

​

​

​

​

aTup = ("apple",5,"banana",3.2) print(aTup[1])

print(aTup[-2])

print(aTup[1:3:1])

​

4

Immutability

• Cannot change element values, i.e., cannot use the assignment operator

​

• Cannot add or remove elements

​

• Can be used to store database records

aTup = ("apple",5,"banana",3.2)

aTuple[1] = "iitd-ad" # Error

5

Tuple Constructor

• Can be used to convert a collection of elements to tuple

​

​

aTup = ("apple",5,"banana",3.2)

print(aTuple)

​

aList = [5, "iitd", 3.2]

print(aList)

​

aTuple = tuple(aList)

print(aTuple)

6

In-Built Methods

• Length

​

aTuple = (5, "iitd", 3.2)

print(len(aTuple))

​

7

Tuple Addition

• Tuples cannot be changed.

​

• However, two tuples can be merged using the addition operator.

aTuple = (5,"iitd",3.2)

bTuple = (2,6)

combinedTuple = aTuple + bTuple

print(combinedTuple)

​

​

8

Example: Swapping Variable Values

• Tuples can be used conveniently to swap variable values.
• (x, y) = (y, x)

​

• It can be used to return more than one value from a function.

​

def quo_and_rem(x, y):

q = x // y

r = x % y

return (q, r)

(quo, rem) = quo_and_rem(42,5)

​

9

Working with Tuples

• Can iterate over tuples

wordTuple = ("Apple", 3, 3.6)

for word in wordTuple:

print(type(word))

10

Tuples vs. Lists

names = ["aadi", "viresh", "amit", "riju", "maya", "tarun"]

marks_col100 = [100, 100, 80, 90, 75, 95]

marks_col106 = [50, 70, 100, 100, 80, 95]

marks_col334 = [93, 86, 63, 74, 76, 75]

marks_avg = [0] * 6

​

for i in range(0, 6):

marks_avg[i]=(marks_col100[i]+marks_col106[i]+marks_col334[i])/3

​

marks = [()] * 6

for i, name in enumerate(names):

marks[i]=(names[i],(marks_col100[i],marks_col106[i],marks_col334[i]),marks_avg[i])

print(marks, type(marks))

print(marks[2][1], type(marks[2][1]))

print(marks[2][1][2], type(marks[2][1][2]))

11

Call by value and call by reference

def remove(val, myList, dummystr, dummytuple):

for (i, val_at_i) in enumerate(myList):

if val == val_at_i and dummystr != "":

myList.pop(i)

val = -1

dummystr = "i protest, i am not a dummy string"

dummytuple = (3, 4, 5)

​

myList = [1, 4, 2, 4, 5, 6, 7]

val = 4

dummystr = "i am a dummy string"

dummytuple = (1, 2, 3)

print(myList, val, dummystr, dummytuple)

remove(val, myList, dummystr, dummytuple)

print(myList, val, dummystr, dummytuple)

12

Plot graphs

expr="x * x"

samples = [(x, eval(expr)) for x in range(-10, 11, 1)]

plt.plot([x for (x, y) in samples], [y for (x, y) in samples])

plt.show()

​

15

Additional examples

• Vector addition or multiplication
• Compute (x, y) tuples to create graphs
• Plot a histogram for y-values of a function
• Create a list of tuples, then do a binary search on the list, find the max in the list, etc.

​

16