SM-2

🧠🔄 Build your own Spaced Repetition System in Python 🧠🔄

Python package implementing the classic SM-2 algorithm for spaced repetition scheduling.

Installation

You can install the sm-2 python package from PyPI using pip:

pip install sm-2

Quickstart

Import and initialize the SM-2 scheduler

from sm_2 import SM2Scheduler, Card, ReviewLog

scheduler = SM2Scheduler()

Create a new Card object

card = Card()

Choose a rating and review the card

"""
5 - perfect response
4 - correct response after a hesitation
3 - correct response recalled with serious difficulty
2 - incorrect response; where the correct one seemed easy to recall
1 - incorrect response; the correct one remembered
0 - complete blackout.
"""

rating = 5

card, review_log = scheduler.review_card(card, rating)

print(f"Card rated {review_log.rating} at {review_log.review_datetime}")
# > Card rated 5 at 2024-10-24 02:14:20.802958+00:00

See when the card is due next

from datetime import datetime, timezone

due = card.due

# how much time between when the card is due and now
time_delta = due - datetime.now(timezone.utc)

print(f"Card due: at {repr(due)}")
print(f"Card due in {time_delta.seconds / 3600} hours")
# > Card due: at datetime.datetime(2024, 10, 25, 2, 14, 20, 799320, tzinfo=datetime.timezone.utc)
# > Card due in 23.99972222222222 hours

Usage

Timezone

SM-2 uses UTC only. You can still specify custom datetimes, but they must be UTC.

from sm_2 import SM2Scheduler, Card, ReviewLog
from datetime import datetime, timezone

scheduler = SM2Scheduler()

# create a new card on Jan. 1, 2024
card = Card(created_at=datetime(2024, 1, 1, 0, 0, 0, 0, timezone.utc)) # right
#card = Card(created_at=datetime(2024, 1, 1, 0, 0, 0, 0)) # wrong

# review the card on Jan. 2, 2024
card, review_log = scheduler.review_card(card=card, rating=5, review_datetime=datetime(2024, 1, 1, 0, 0, 0, 0, timezone.utc)) # right
#card, review_log = scheduler.review_card(card=card, rating=5, review_datetime=datetime(2024, 1, 1, 0, 0, 0, 0)) # wrong

Serialization

Card and ReviewLog objects are json-serializable via their to_dict and from_dict methods for easy database storage:

# serialize before storage
card_dict = card.to_dict()
review_log_dict = review_log.to_dict()

# deserialize from dict
card = Card.from_dict(card_dict)
review_log = ReviewLog.from_dict(review_log_dict)

Versioning

This python package is currently unstable and adheres to the following versioning scheme:

• Minor version will increase when a backward-incompatible change is introduced.
• Patch version will increase when a bug is fixed or a new feature is added.

Once this package is considered stable, the Major version will be bumped to 1.0.0 and will follow semver.

Contribute

Checkout CONTRIBUTING to help improve sm-2!