Iterables

Sequences in Python

Sequences are a fundamental data structure in Python. They are ordered collections of items, meaning that the order in which items are added matters, and each item has a specific index. Several built-in types in Python are sequences.

Key characteristics:

• Ordered: Items maintain their relative positions.
• Iterable: You can loop through the items using for loops.
• Indexable: You can access items using their index (starting from 0).
• Slicable: You can extract portions of the sequence using slicing.

Common Sequence Types:

• Lists: Mutable (changeable) sequences. 1, 2, 'a', True]]

my_list = 1, 2, 3
my_list.append(4)  # Add an item
my_list[0]] = 10   # Change an item

• Tuples: Immutable (unchangeable) sequences. (1, 2, 'a', True)

my_tuple = (1, 2, 3)
# my_tuple.append(4)  # This would raise an error because tuples are immutable

• Strings: Sequences of characters. "Hello, world!"

my_string = "Python"
my_string[0]]  # Accesses 'P'

• Ranges: Sequences of numbers. range(10) generates numbers 0-9.

for i in range(5):
    print(i) # prints 0, 1, 2, 3, 4

• bytes and bytearrays: Sequences of bytes.

Sequence Operations:

Many operations work consistently across different sequence types:

• Indexing: Accessing individual elements using their index (e.g., my_list2).
• Slicing: Extracting a portion of the sequence (e.g., my_list1:3). (Slicing)
• Concatenation: Combining sequences using the + operator (e.g., list1 + list2).
• Membership testing: Checking if an item is present using in or not in (e.g., 'a' in my_string).
• Iteration: Looping through the elements using a for loop.
• Length: Getting the number of items using len() (e.g., len(my_list)).

Further Notes:

• Mutability
• Immutability
• Iteration in Python