Python List

 # Python List Examples

# ── Creating lists ────────────────────────────────────────────────────────────

empty_list = []

numbers = [1, 2, 3, 4, 5]

mixed = [42, "hello", 3.14, True]

nested = [[1, 2], [3, 4], [5, 6]]

from_range = list(range(1, 6)) # [1, 2, 3, 4, 5]

# ── Indexing and slicing ──────────────────────────────────────────────────────

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

print(fruits[0]) # apple

print(fruits[-1]) # elderberry

print(fruits[1:3]) # ['banana', 'cherry']

print(fruits[:3]) # ['apple', 'banana', 'cherry']

print(fruits[2:]) # ['cherry', 'date', 'elderberry']

print(fruits[::2]) # ['apple', 'cherry', 'elderberry']

print(fruits[::-1]) # ['elderberry', 'date', 'cherry', 'banana', 'apple']

# ── List methods ──────────────────────────────────────────────────────────────

colors = ["red", "green", "blue"]

colors.append("yellow") # colors → ['red', 'green', 'blue', 'yellow']

colors.insert(1, "orange") # colors → ['red', 'orange', 'green', 'blue', 'yellow']

colors.remove("green") # colors → ['red', 'orange', 'blue', 'yellow']

popped = colors.pop() # popped → 'yellow' | colors → ['red', 'orange', 'blue']

popped_at = colors.pop(1) # popped_at → 'orange' | colors → ['red', 'blue']

nums = [3, 1, 4, 1, 5, 9, 2, 6]

nums.sort() # nums → [1, 1, 2, 3, 4, 5, 6, 9]

nums.sort(reverse=True) # nums → [9, 6, 5, 4, 3, 2, 1, 1]

sorted_copy = sorted(nums) # sorted_copy → [1, 1, 2, 3, 4, 5, 6, 9] | nums unchanged

nums.reverse() # nums → [1, 1, 2, 3, 4, 5, 6, 9]

print(nums.count(1)) # 2

print(nums.index(5)) # 5

nums.extend([10, 11]) # nums → [1, 1, 2, 3, 4, 5, 6, 9, 10, 11]

nums.clear() # nums → []

# ── Iterating through lists ───────────────────────────────────────────────────

animals = ["cat", "dog", "fish"]

# Basic for loop

for animal in animals:

print(animal)

# cat

# dog

# fish

# With index using enumerate

for i, animal in enumerate(animals):

print(f"{i}: {animal}")

# 0: cat

# 1: dog

# 2: fish

# While loop

i = 0

while i < len(animals):

print(animals[i])

i += 1

# cat

# dog

# fish

# List comprehension (create a new list while iterating)

squares = [x ** 2 for x in range(1, 6)] # [1, 4, 9, 16, 25]

evens = [x for x in range(1, 11) if x % 2 == 0] # [2, 4, 6, 8, 10]

# Iterating over two lists in parallel

names = ["Alice", "Bob", "Charlie"]

scores = [95, 87, 92]

for name, score in zip(names, scores):

print(f"{name}: {score}")

# Alice: 95

# Bob: 87

# Charlie: 92