Lists

A list is an ordered collection of elements that can hold items of different types.

Key characteristics:

• Elements: Can be of any data type.
• Order: Maintains a specific sequence.

Creating Lists

There are two primary ways to create lists:

Method 1: Initialize an empty list and add elements one by one.

>>> devices = list()
>>> devices.append("Samsung")
>>> devices.append("Sony")
>>> devices.append("LG")
>>> devices
['Samsung', 'Sony', 'LG']

Method 2: Define the list directly with initial values.

>>> devices = ["Samsung", "Sony", "LG"]
>>> devices
['Samsung', 'Sony', 'LG']

Manipulating Lists

Retrieving Elements

Access elements using index notation [i], where i starts from zero.

>>> devices = ["Samsung", "Sony", "LG"]
>>> devices[0]
'Samsung'
>>> devices[1]
'Sony'
>>> devices[2]
'LG'

Use the index() method to find the first occurrence of a value.

>>> devices = ["Samsung", "Sony", "LG", "Sony"]
>>> devices.index("Sony")
1

Adding Elements

Several methods exist for appending elements:

• append(): Adds an element to the end of the list.

>>> devices = []
>>> devices
[]
>>> devices.append("Samsung")
>>> devices
['Samsung']
>>> devices.append("Sony")
>>> devices
['Samsung', 'Sony']

• insert(index, item): Inserts an element at a specified position.

>>> devices = ["Samsung", "Sony", "LG"]
>>> devices.insert(1, "Apple")
>>> devices
['Samsung', 'Apple', 'Sony', 'LG']

• extend(): Appends all elements from another iterable to the list.

>>> devices = ["Samsung", "Sony", "LG"]
>>> more_devices = ["Apple", "Nokia"]
>>> devices.extend(more_devices)
>>> devices
['Samsung', 'Sony', 'LG', 'Apple', 'Nokia']

Modifying Elements

Direct assignment replaces an existing element.

>>> devices = ["Samsung", "Sony", "LG"]
>>> devices[1] = "Apple"
>>> devices
['Samsung', 'Apple', 'LG']

Removing Elements

Various techniques are available for removing elements:

• pop([index]): Removes and returns an element at a given index (default is last).

>>> devices = ["Samsung", "Sony", "LG"]
>>> devices.pop()
'LG'
>>> devices.pop(0)
'Samsung'
>>> devices
['Sony']

• remove(value): Deletes the first occurrence of a value.

>>> devices = ["Samsung", "Sony", "LG", "Sony"]
>>> devices.remove("Sony")
>>> devices
['Samsung', 'LG', 'Sony']

• clear(): Empties the entire list.

>>> devices = ["Samsung", "Sony", "LG"]
>>> devices.clear()
>>> devices
[]

• del: Removes elements by slicing or index.

>>> devices = ["Samsung", "Sony", "LG"]
>>> del devices[:]
>>> devices
[]

List Reversal

Two approaches to reverse a list:

Using reverse() method:

>>> numbers = [1, 2, 3, 4, 5]
>>> numbers.reverse()
>>> numbers
[5, 4, 3, 2, 1]

Using slicing:

>>> numbers = [1, 2, 3, 4, 5]
>>> numbers[::-1]
[5, 4, 3, 2, 1]

The difference between these methods is:

• reverse() modifies the original list in place.
• Slicing creates a new reversed list without altering the original.

Sorting Lists

Lists support built-in sorting via the sort() method.

>>> data = [4, 8, 1, 7, 2]
>>> data.sort()
>>> data
[1, 2, 4, 7, 8]

Tuples

Tuples are immutable sequences, typically containing heterogeneous elements.

Creating Tuples

Method 1: Use parentheses to define a tuple.

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

Method 2: Parentheses are optional when creating tuples.

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

To create a single-element tuple, include a trailing comma:

>>> ctuple = (1,)
>>> type(ctuple)
<class 'tuple'>
>>> ctuple
(1,)

>>> dtuple = 1,
>>> type(dtuple)
<class 'tuple'>
>>> dtuple
(1,)

A empty tuple can be created like so:

>>> a = tuple()
>>> a
()
>>> b = ()
>>> b
()

Since tuples are immutable, they do not support modification operations.

Converting Between Lists and Tuples

Converting from tuple to list:

>>> atuple = (1, 2, 3, 4)
>>> list(atuple)
[1, 2, 3, 4]

Converting from list to tuple:

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