Based on Aaronson Oracle

oracle.py

import sys
import getch
from collections import defaultdict


class Oracle:
    def __init__(self, window_size: int):
        self.window_size = window_size
        self.window: str = ''
        self.patterns: defaultdict[str, dict[str, int]] = defaultdict(lambda: defaultdict(int))


    def observe(self, c: str):
        if len(c) != 1:
            return

        self.window += c
        if len(self.window) <= self.window_size:
            return

        key = self.window[:-1]
        self.patterns[key][c] += 1
        self.window = self.window[1:]


    def predict(self, default: str) -> str:
        if self.window not in self.patterns:
            return default

        return max(self.patterns[self.window].items(), key=lambda x: x[1])[0]


def main():
    print('Press any of "j" or "f" repeatedly, I will try to predict your keystrokes.')
    print('Press Escape to exit.')
    total = 0
    good = 0
    oracle = Oracle(4)
    while True:
        c = oracle.predict('f')
        print('> ', end='')
        sys.stdout.flush()
        s = getch.getch()
        if ord(s) == 27:
            break
        s = 'f' if s == 'f' else 'j'
        print(s, end='\t')
        oracle.observe(s)
        total += 1
        if s == c:
            good += 1
        print(f'{100 * good / total:.0f}%')
        sys.stdout.flush()


main()

pip install getch