Section 2: Python Data Structures

Lecture 2.1: Lists and Tuples

What is a List?

In Python data structure, a list refers to a collection of items that are ordered and malleable, i.e., they can be changed.

Lists are heterogeneous in nature, as they can contain elements of different data types such as integer, string, or even another list.

syntax:

my_list = [1, 2, 3, "apple", 4.5]

What is a Tuple?

Tuple refers to a structured set of elements that are nevertheless immutable and thus cannot be modified post-creation.

syntax:

my_tuple = (1, 2, 3, "apple", 4.5)

Feature	List	Tuple
Feature	List	Tuple
Mutability	Mutable (can change)	Immutable (unchangeable)
Syntax	[ ]	( )
Usage	When frequent changes are needed	When data integrity is crucial

List and Tuple Operations:

Indexing

Both lists and tuples are indexed, starting at 0 for the first element.

Accessing Items:

my_list = [10, 20, 30]
print(my_list[1])  # Output: 20

my_tuple = (10, 20, 30)
print(my_tuple[1])  # Output: 20

Slicing:

You can extract specific elements of a list, or a tuple by using slicing.

Syntax: [start:end:step]

my_list = [10, 20, 30, 40, 50]
print(my_list[1:4])   # Output: [20, 30, 40]
print(my_list[::2])   # Output: [10, 30, 50]

my_tuple = (10, 20, 30, 40, 50)
print(my_tuple[1:4])  # Output: (20, 30, 40)

Iteration:

Elements can be traversed by iterating over them in the for loops.

• Example with a list:

for item in [1, 2, 3]:
    print(item)
# Output:
# 1
# 2
# 3

• Example with a Tuple:

for item in (4, 5, 6):
    print(item)
# Output:
# 4
# 5
# 6

Built-in Functions:

Python contributes with quite a few built-in functions that are helpful for both lists and tuples.

len()

Returns the total number of elements in the list or tuple.

Example:

my_list = [1, 2, 3]
print(len(my_list)) # Output: 3

my_tuple = (4, 5, 6)
print(len(my_tuple)) # Output: 3

min()

Returns the smallest element in the list or tuple.

Example:

my_list = [10, 20, 5, 40]
print(min(my_list)) # Output: 5

my_tuple = (100, 200, 50)
print(min(my_tuple)) # Output: 50

max()

Returns the largest element in the list or tuple.

Example:

my_list = [10, 20, 5, 40]
print(max(my_list))  # Output: 40

my_tuple = (100, 200, 50)
print(max(my_tuple)) # Output: 200