Lists in Python

# Different ways to create lists

# Empty list
my_list = []
print("Empty:", my_list)

# List with strings
fruits = ["apple", "banana", "cherry"]
print("Fruits:", fruits)

# List with numbers
numbers = [10, 20, 30, 40, 50]
print("Numbers:", numbers)

# Mixed types
mixed = [1, "hello", True, 3.14]
print("Mixed:", mixed)

# How many items?
print(f"Fruits has {len(fruits)} items")

fruits = ["apple", "banana", "cherry", "date"]

# Positive indexing (from start)
print("First item:", fruits[0])
print("Second item:", fruits[1])
print("Third item:", fruits[2])

# Negative indexing (from end)
print("Last item:", fruits[-1])
print("Second to last:", fruits[-2])

# Get length of list
print(f"Total items: {len(fruits)}")

colors = ["red", "green", "blue"]
print("Original:", colors)

# Change single item
colors[0] = "yellow"
print("After change:", colors)

# Change last item
colors[-1] = "purple"
print("After another change:", colors)

fruits = ["apple", "banana"]
print("Start:", fruits)

# append - add to end
fruits.append("cherry")
print("After append:", fruits)

# insert - add at specific position
fruits.insert(1, "blueberry")
print("After insert at 1:", fruits)

# extend - add multiple items
fruits.extend(["date", "elderberry"])
print("After extend:", fruits)

fruits = ["apple", "banana", "cherry", "banana", "date"]
print("Start:", fruits)

# remove - by value (first occurrence only)
fruits.remove("banana")
print("After remove banana:", fruits)

# pop - remove and return last item
last = fruits.pop()
print(f"Popped: {last}, Remaining:", fruits)

# pop(0) - remove first item
first = fruits.pop(0)
print(f"Popped first: {first}, Remaining:", fruits)

nums = [0, 1, 2, 3, 4, 5]
print("Original:", nums)

# Get a range
print("nums[1:4]:", nums[1:4])   # [1, 2, 3]

# From start / to end
print("nums[:3]:", nums[:3])     # [0, 1, 2]
print("nums[3:]:", nums[3:])     # [3, 4, 5]

# Negative slicing
print("Last 2:", nums[-2:])      # [4, 5]

# With step
print("Every 2nd:", nums[::2])   # [0, 2, 4]
print("Reversed:", nums[::-1])   # [5, 4, 3, 2, 1, 0]

fruits = ["apple", "banana", "cherry"]

# Simple loop - just items
print("Simple loop:")
for fruit in fruits:
    print(fruit)

# With index using enumerate
print("\nWith index:")
for i, fruit in enumerate(fruits):
    print(f"{i}: {fruit}")

# Start counting from 1 instead of 0
print("\nNumbered list:")
for num, fruit in enumerate(fruits, start=1):
    print(f"{num}. {fruit}")

numbers = [5, 2, 8, 1, 9, 2, 5]
print("Original:", numbers)

# Sorting
numbers.sort()
print("Sorted:", numbers)

numbers.sort(reverse=True)
print("Descending:", numbers)

# Counting
print(f"Count of 5: {numbers.count(5)}")

# With number lists
nums = [10, 20, 30, 40]
print(f"Sum: {sum(nums)}")
print(f"Min: {min(nums)}, Max: {max(nums)}")
print(f"Average: {sum(nums) / len(nums)}")

fruits = ["apple", "banana", "cherry"]

# Check if item exists
if "banana" in fruits:
    print("Yes, banana is in the list!")

if "grape" not in fruits:
    print("No, grape is NOT in the list")

# Practical use: safe removal
item_to_remove = "orange"
if item_to_remove in fruits:
    fruits.remove(item_to_remove)
else:
    print(f"{item_to_remove} not found in list")

# Basic list comprehension
squares = [x ** 2 for x in range(6)]
print("Squares:", squares)

# With condition - only even numbers
evens = [x for x in range(10) if x % 2 == 0]
print("Evens:", evens)

# Transform items
words = ["hello", "world", "python"]
upper_words = [word.upper() for word in words]
print("Uppercase:", upper_words)

# Get lengths
lengths = [len(word) for word in words]
print("Lengths:", lengths)