D. Removing Items with remove()

← C. Adding with append() ⏱️ 5 min E. Loops and Lists →

🎯 Learning Goals

By the end of this lesson, you'll be able to:

○ remove() function to remove items
○ Be able to remove enemies/bullets in a game
○ Understand the cautions when removing

Core Concepts

What is remove()?

remove() function removes a specific item from a list.

🗑️ Analogy: a trash can

Just like Trash canLike throwing something into a trash can! It finds the specified item and removes it.

fruits = ["Apple", "Banana", "Orange"]
fruits.remove("Banana")
# fruits = ["사과", "오렌지"]

Syntax

list name.remove(to remove Item)

Using it in games

enemies = [enemy1, enemy2, enemy3]

# Remove when an enemy dies
enemies.remove(enemy1)
destroy(enemy1)  # Remove from the screen too

Cautions

⚠️ Caution!

In the list, an item that isn't there trying to remove it causes an error!

fruits = ["Apple", "Banana"]
fruits.remove("Grape")  # ValueError!

Example Code

from ursina import *

app = Ursina()

# Target list
targets = []

# Create 6 targets
for i in range(6):
    target = Entity(
        model='cube',
        color=color.white,
        position=(i*2 - 5, 0, 5)
    )
    targets.append(target)

print(f"Target count: {len(targets)}")  # 6

# Remove the first target
first = targets[0]
targets.remove(first)
destroy(first)

print(f"Target count: {len(targets)}")  # 5

app.run()

What Happens

1 of 6 is removed, leaving 5!

Quiz

Quiz: remove() cautions

What happens if you try to remove an item that isn't in the list?

Show Answer

Answer: B) A ValueError occurs

Trying to remove an item that isn't there causes an error! It's safer to check whether the item exists before removing it.

remove() practice:

fruits = ["사과", "바나나", "오렌지"] Given a list:

"바나나" to remove it: fruits. ("바나나") → ["사과", "오렌지"]
If you remove an item that isn't in the list: Occurs
Before removing, "포도" check whether it exists: if "포도" fruits:

🔧 Debug Clinic

Problem: `ValueError: list.remove(x): x not in list`

❌ Wrong Code

targets.remove(enemy)  # Error if enemy isn't in targets!

Cause: Trying to remove an item that isn't in the list

✅ Correct Code

if enemy in targets:
    targets.remove(enemy)

Fix: Before removing, in keyword to check!

Try Coding It Yourself

Take what you learned with the blocks and write it yourself in Python code!

Removing with remove()

Remove a specific item from the list.

Example Answer

fruits = ['Apple', 'Banana', 'Orange', 'Grape']
print(f'Before removing: {fruits}')
fruits.remove('Banana')
print(f'After removing: {fruits}')

Result: The list with '바나나' removed is printed!

Removing safely

Check whether the item exists, then remove it!

🧩 Key Takeaways

What you learned in this lesson:

Concept	Description
remove()	Remove an item from a list
Syntax	`list.remove(item)`
Caution	Error when removing a nonexistent item
Safety check	`if item in list:`

Review Checklist

[ ] remove() Can you explain the role of the function?
[ ] Do you know which error occurs when you try to remove a nonexistent item?
[ ] in keyword, can you check whether an item exists?