List Methods: Managing Collections 📝

Lists are not just storage. They come with built-in actions (methods) that let you add, remove, and modify elements.

🎯 What Are Methods?

A method is an action that an object can perform.

Syntax:

object.method()

For example:

my_list.append(5)  # Call the append method on my_list

➕ append() — Add to the End

The most common method! Adds an element to the END of the list:

hand = ["🐲 Dragon", "🧙 Mage"]

print(hand)  # ['🐲 Dragon', '🧙 Mage']

hand.append("⚔️ Knight")

print(hand)  # ['🐲 Dragon', '🧙 Mage', '⚔️ Knight']

Where to use it:
- Dealing cards into a hand
- Adding a new player
- Collecting scores

Example: Dealing cards

import random

creatures = [
    {"name": "🐲 Dragon", "attack": 8},
    {"name": "🧙 Mage", "attack": 6},
    {"name": "⚔️ Knight", "attack": 5}
]

player_hand = []

# Deal 3 cards
for i in range(3):
    card = random.choice(creatures)
    player_hand.append(card)
    print(f"Card received: {card['name']}")

print(f"\nTotal cards in hand: {len(player_hand)}")

❌ remove() — Remove by Value

Removes the FIRST occurrence of the given value:

inventory = ["Sword", "Shield", "Potion", "Sword"]

print(inventory)  # ['Sword', 'Shield', 'Potion', 'Sword']

inventory.remove("Sword")  # Removes the FIRST sword

print(inventory)  # ['Shield', 'Potion', 'Sword']

⚠️ Important: If the element is not in the list — it raises an error!

items = ["Sword", "Shield"]

items.remove("Bow")  # ❌ ValueError: 'Bow' not in list

Safe approach:

items = ["Sword", "Shield"]

if "Bow" in items:
    items.remove("Bow")
else:
    print("No bow in inventory")

Example: Removing a defeated card

enemy_hand = [
    {"name": "🐲 Dragon", "health": 12},
    {"name": "🧙 Mage", "health": 0},  # Defeated!
    {"name": "⚔️ Knight", "health": 10}
]

for card in enemy_hand:
    if card["health"] <= 0:
        print(f"💀 {card['name']} has been defeated!")
        enemy_hand.remove(card)
        break  # Important! Don't modify a list while iterating over it

print(f"Enemy cards remaining: {len(enemy_hand)}")

🎯 pop() — Extract and Remove

Removes an element BY INDEX and RETURNS it:

cards = ["🐲 Dragon", "🧙 Mage", "⚔️ Knight"]

# Take the last card
last_card = cards.pop()
print(f"Took: {last_card}")  # ⚔️ Knight
print(cards)  # ['🐲 Dragon', '🧙 Mage']

# Take the first card
first_card = cards.pop(0)
print(f"Took: {first_card}")  # 🐲 Dragon
print(cards)  # ['🧙 Mage']

No argument — removes the last element
With an index — removes the element at that index

Example: Player turn

player_hand = [
    {"name": "🐲 Dragon", "attack": 8},
    {"name": "🧙 Mage", "attack": 6},
    {"name": "⚔️ Knight", "attack": 5}
]

print("Your hand:")
for i, card in enumerate(player_hand):
    print(f"{i+1}. {card['name']}")

choice = int(input("\nChoose a card (1-3): "))
selected_card = player_hand.pop(choice - 1)

print(f"\n⚔️ You played: {selected_card['name']}")
print(f"Cards remaining: {len(player_hand)}")

🔍 Checking Membership: in

Before removing or searching — check whether the element is present:

inventory = ["Sword", "Shield", "Potion"]

if "Sword" in inventory:
    print("✅ You have a sword!")
else:
    print("❌ No sword")

if "Bow" not in inventory:
    print("You have no bow")

📏 len() — Number of Elements

Find out how many elements are in the list:

hand = ["🐲 Dragon", "🧙 Mage", "⚔️ Knight"]

print(f"Cards in hand: {len(hand)}")  # 3

if len(hand) == 0:
    print("Hand is empty!")

Checking for an empty list:

if len(hand) > 0:
    print("Has cards")

# Or shorter:
if hand:  # Empty list evaluates to False
    print("Has cards")

🔄 clear() — Empty the List

Removes ALL elements:

hand = ["🐲 Dragon", "🧙 Mage", "⚔️ Knight"]

print(hand)  # ['🐲 Dragon', '🧙 Mage', '⚔️ Knight']

hand.clear()

print(hand)  # []
print(f"Cards remaining: {len(hand)}")  # 0

📊 Methods Reference Table

💪 Practical Examples

Example 1: Inventory

inventory = []

# Add items
inventory.append("Sword")
inventory.append("Shield")
inventory.append("Potion")

print(f"Inventory: {inventory}")

# Use a potion
if "Potion" in inventory:
    inventory.remove("Potion")
    print("💊 Potion used!")

print(f"Remaining: {inventory}")

Example 2: Action Queue

actions_queue = ["attack", "defend", "heal", "power_attack"]

while len(actions_queue) > 0:
    current_action = actions_queue.pop(0)  # Take the first
    print(f"⚔️ Executing: {current_action}")

print("All actions executed!")

Example 3: Card Deck

deck = [
    {"name": "🐲 Dragon", "attack": 8},
    {"name": "🧙 Mage", "attack": 6},
    {"name": "⚔️ Knight", "attack": 5},
    {"name": "🧚 Fairy", "attack": 3}
]

hand = []

# Draw 2 cards from the deck
for i in range(2):
    card = deck.pop(0)   # Take the top card from the deck
    hand.append(card)    # Add to hand
    print(f"Drew card: {card['name']}")

print(f"\nCards in deck: {len(deck)}")
print(f"Cards in hand: {len(hand)}")

⚠️ Important Gotchas

1. Don’t modify a list while iterating over it

# ❌ WRONG!
items = ["A", "B", "C", "D"]
for item in items:
    if item == "B":
        items.remove(item)  # May skip elements!

# ✅ CORRECT: iterate over a copy
items = ["A", "B", "C", "D"]
for item in items[:]:  # [:] creates a copy
    if item == "B":
        items.remove(item)

2. remove() vs pop()

# remove() — deletes by VALUE
hand = ["Sword", "Shield", "Potion"]
hand.remove("Shield")  # Removed "Shield"

# pop() — deletes by INDEX
hand = ["Sword", "Shield", "Potion"]
hand.pop(1)  # Removed element at index 1 (also "Shield")

3. Methods modify the list in place

numbers = [1, 2, 3]
numbers.append(4)  # Modifies numbers directly
print(numbers)  # [1, 2, 3, 4]

# Methods do NOT return a new list (except pop)
result = numbers.append(5)
print(result)  # None

🎯 Summary

Core methods:
- ✅ .append(x) — add an element
- ✅ .remove(x) — remove by value
- ✅ .pop() — take and remove
- ✅ .clear() — empty the list
- ✅ len(list) — get the size
- ✅ x in list — check membership

Remember:
- Methods are called with dot notation: list.method()
- append adds to the end
- remove deletes by value (first occurrence)
- pop deletes by index and returns the element
- Check membership before removing!
- Use len() to check the size of a list