Lists (list)

Lists are ordered, mutable sequences defined with square brackets []. You can add, remove, or change items after creation.

Characteristics and Use Cases

• Ordered: items maintain position
• Mutable: .append(), .insert(), .pop(), .remove()
• Ideal for storing sequences where order matters and contents change (e.g., list of servers, deployment steps)

Accessing Items and Slicing

• Access single elements with my_list[index] (0-based). Use negative indices like my_list[-1] for the last item.
• Slice with my_list[start:stop] to get a sub-list from start up to (but not including) stop.
• Use three-parameter slicing my_list[start:stop:step] for stepping, e.g., my_list[::2] selects every other element.
• Omitting start or stop defaults to the beginning or end of the list respectively, and slicing returns a new list without modifying the original.

servers = ["web01", "web02", "web03"]
mixed_list = ["config.yaml", 8080, True]

for item in mixed_list:
    print(type(item))

print(servers[0])
# print(servers[3]) # Commenting this out will raise an IndexError Exception
print(servers[-1])
print(servers[-2])

# Slicing
print(servers[:2]) # Will print only elements at indexes 0 and 1
print(servers[1:]) # Will print only elements at indexes 1 and 2
print(servers[-2:]) # Will print only the second to last and last elements
# Slicing does not alter the original list
print(servers)

# Mutating lists
ports = [80, 443, 8080]
ports.append(5000)
print(ports)
ports.insert(1, 3000)
print(ports)
ports.remove(80)
print(ports)
removed_value = ports.pop(2)
print(ports)
print(removed_value)

# Example to show how mutating lists can lead to side-effects outside of
# the scope of the code that modifies the list.
def mutate_list(l):
    l.pop()

new_list = ["a", "b", "c"]
mutate_list(new_list)
print(new_list)