import subprocess
import csv


def available_gpu() -> str:
    """
    return indices of not occupied (memory usage less than 200 MiB) GPUs
    """
    with open('gpu_usage.txt', 'w+') as gpu_usage:
        subprocess.run(['nvidia-smi',
                        '--query-gpu=index,memory.used',
                        '--format=csv,noheader,nounits'],
                       stdout=gpu_usage)

    with open('gpu_usage.txt', 'r') as gpu_usage:
        gpus = csv.reader(gpu_usage, delimiter=',')
        for gpu in gpus:
            if int(gpu[1]) < 200:
                subprocess.run(['rm', 'gpu_usage.txt'])
                return gpu[0]
        raise ValueError('There is no available GPU')