import subprocess
import os
import errno

def download_file(url, local_fname=None, force_write=False):
    # requests is not default installed
    import requests
    if local_fname is None:
        local_fname = url.split('/')[-1]
    if not force_write and os.path.exists(local_fname):
        return local_fname

    dir_name = os.path.dirname(local_fname)

    if dir_name != "":
        if not os.path.exists(dir_name):
            try: # try to create the directory if it doesn't exists
                os.makedirs(dir_name)
            except OSError as exc:
                if exc.errno != errno.EEXIST:
                    raise

    r = requests.get(url, stream=True)
    assert r.status_code == 200, "failed to open %s" % url
    with open(local_fname, 'wb') as f:
        for chunk in r.iter_content(chunk_size=1024):
            if chunk: # filter out keep-alive new chunks
                f.write(chunk)
    return local_fname

def get_gpus():
    """
    return a list of GPUs
    """
    try:
        re = subprocess.check_output(["nvidia-smi", "-L"], universal_newlines=True)
    except OSError:
        return []
    return range(len([i for i in re.split('\n') if 'GPU' in i]))