Это потому, что modified_result
- это массив, а не число:
possible_rolls = arr = np.array([1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20])
roll_result = np.random.choice(possible_rolls,1,replace=True)
modified_result = roll_result + 11
action_succeeded = modified_result > 15
print(type(modified_result))
>>> <class 'numpy.ndarray'>
Это решит проблему:
print("On a modified roll of {:d}, Alice's action {}.".format(modified_result[0], "succeeded" if action_succeeded else "failed"))
>>> On a modified roll of 13, Alice's action failed.