brain_games/games/progression.py
from random import randint
GAME_RULE = 'What number is missing in the progression?'
def get_question_and_answer():
start = randint(0, 10)
step = randint(1, 10)
length = randint(5, 10)
stop = start + length * step
missing_number_index = randint(0, length - 1)
progression = list(range(start, stop, step))
answer = str(progression[missing_number_index])
progression[missing_number_index] = '..'
task = ' '.join(map(str, progression))
return (task, answer)