05_lists_tutorial.py

# 1. Creating lists
# List - ordered mutable collection of elements
empty_list = []
numbers = [1, 2, 3, 4, 5]
mixed = [1, "text", 3.14, True, [1, 2]]  # Can contain different types

print(f"Empty list: {empty_list}")
print(f"Numbers: {numbers}")
print(f"Mixed list: {mixed}")

# 2. Accessing elements (indexing)
fruits = ["apple", "banana", "orange", "pear"]

print(f"First element: {fruits[0]}")       # apple
print(f"Last element: {fruits[-1]}")   # pear
print(f"Second from end: {fruits[-2]}")      # orange

# 3. Slicing
print(f"First two elements: {fruits[0:2]}")     # ['apple', 'banana']
print(f"From third to end: {fruits[2:]}")      # ['orange', 'pear']
print(f"Last two: {fruits[-2:]}")           # ['orange', 'pear']
print(f"Every second: {fruits[::2]}")           # ['apple', 'orange']
print(f"In reverse order: {fruits[::-1]}")     # ['pear', 'orange', 'banana', 'apple']

# 4. Modifying elements
numbers = [1, 2, 3, 4, 5]
numbers[0] = 10         # Change first element
print(f"After modification: {numbers}")

numbers[1:3] = [20, 30]  # Change slice
print(f"After slice modification: {numbers}")

# 5. Adding elements
fruits = ["apple", "banana"]

# append() - add to end
fruits.append("orange")
print(f"After append: {fruits}")

# insert() - insert at specific position
fruits.insert(1, "pear")  # Insert at index 1
print(f"After insert: {fruits}")

# extend() - add multiple elements
fruits.extend(["kiwi", "mango"])
print(f"After extend: {fruits}")

# Alternative to extend - concatenation
fruits = fruits + ["lemon"]
print(f"After concatenation: {fruits}")

# 6. Removing elements
numbers = [1, 2, 3, 4, 5, 3]

# remove() - remove first occurrence of value
numbers.remove(3)  # Will remove first 3
print(f"After remove(3): {numbers}")

# pop() - remove by index and return value
last = numbers.pop()     # Without argument removes last
print(f"Removed: {last}, remaining: {numbers}")

second = numbers.pop(1)  # Remove element at index 1
print(f"Removed: {second}, remaining: {numbers}")

# del - delete element or slice
numbers = [1, 2, 3, 4, 5]
del numbers[0]        # Delete first element
print(f"After del: {numbers}")

# clear() - clear entire list
numbers.clear()
print(f"After clear: {numbers}")

# 7. Finding elements
fruits = ["apple", "banana", "orange", "banana"]

# in - check presence
print(f"'banana' in fruits: {'banana' in fruits}")    # True

# index() - find index of first occurrence
index = fruits.index("banana")
print(f"Index of 'banana': {index}")

# count() - count number of occurrences
count = fruits.count("banana")
print(f"Count of 'banana': {count}")

# 8. Sorting
numbers = [5, 2, 8, 1, 9, 3]

# sort() - sorts list in place (modifies original)
numbers.sort()
print(f"After sort(): {numbers}")

numbers.sort(reverse=True)  # In reverse order
print(f"After sort(reverse=True): {numbers}")

# sorted() - returns new sorted list (doesn't modify original)
original = [5, 2, 8, 1]
sorted_list = sorted(original)
print(f"Original: {original}, sorted: {sorted_list}")

# 9. Other useful methods
numbers = [1, 2, 3]

# reverse() - reverse list
numbers.reverse()
print(f"After reverse(): {numbers}")

# copy() - create copy of list
copy = numbers.copy()
print(f"Copy: {copy}")

# 10. List length
print(f"len(fruits): {len(fruits)}")

# 11. Lists as stack (LIFO - Last In, First Out)
stack = []
stack.append(1)  # Push to stack
stack.append(2)
stack.append(3)
print(f"Stack: {stack}")

top = stack.pop()  # Pop from stack
print(f"Popped: {top}, remaining: {stack}")

# 12. Multidimensional lists (lists of lists)
matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

print(f"First row: {matrix[0]}")
print(f"Element [1][2]: {matrix[1][2]}")  # 6

# 13. List unpacking
fruits = ["apple", "banana", "orange"]
first, second, third = fruits
print(f"first: {first}, second: {second}, third: {third}")

# With * you can collect remaining elements
numbers = [1, 2, 3, 4, 5]
first, *rest, last = numbers
print(f"first: {first}, rest: {rest}, last: {last}")