Python 3.X装饰器返回None

Question

I have a function which reads a filepath and determines if its local or not (S3). I created a decorator to copy the file locally if the file is in S3. When decorator is applied function is not returning anything (None).

from functools import wraps

def handle_s3_download(fcn):
    @wraps(fcn)
    def inner(data_fp, *args, **kwargs):
        # Handle S3 path
        if data_fp.startswith('s3://'):
            local_data_fp = os.path.join(FOLDER,
                                         os.path.basename(data_fp))
            # Copy file only if necessary.
            if not os.path.isfile(local_data_fp):
                copy_file_from_s3(data_fp, local_data_fp)
            data_fp = local_data_fp
        # Call decorated function
        fcn(data_fp, *args, **kwargs)
    return inner

# Returns None
@handle_s3_download
def load_csv(data_fp):
   data = []
   with open(data_fp, 'rb') as f:
     data = list(csv.reader(f))
   return data


def load_json(data_fp):
    data = []
    if data_fp.startswith('s3://'):
        local_data_fp = os.path.join(FOLDER,
                                     os.path.basename(data_fp))
        # Copy file only if necessary.
        if not os.path.isfile(local_data_fp):
            copy_file_from_s3(data_fp, local_data_fp)
        data_fp = local_data_fp
    with open(data_fp, 'r') as input_file:
        data = json.load(input_file)
    logging.info('Returning data...')
    return data

load_csv('s3://test/test.csv')  # Doesn't work
load_json('s3://test/test.csv')  # Works

Answer 1

If me, I would like to code as follows:

from functools import wraps
from pathlib import Path


def handle_s3_download(fcn):
    @wraps(fcn)
    def inner(data_fp, *args, **kwargs):
        # Handle S3 path
        if data_fp.startswith("s3://"):
            local_data_fp = Path(FOLDER) / os.path.basename(data_fp)
            # Copy file only if necessary.
            if not local_data_fp.is_file():
                copy_file_from_s3(data_fp, str(local_data_fp))
            data_fp = str(local_data_fp)
        # Call decorated function
        return fcn(data_fp, *args, **kwargs)

    return inner


# Returns None
@handle_s3_download
def load_csv(data_fp):
    data = list(csv.reader(Path(data_fp).read_bytes()))
    return data


def load_json(data_fp):
    if data_fp.startswith("s3://"):
        local_data_fp = os.path.join(FOLDER, os.path.basename(data_fp))
        # Copy file only if necessary.
        if not os.path.isfile(local_data_fp):
            copy_file_from_s3(data_fp, local_data_fp)
        data_fp = local_data_fp
    data = json.loads(Path(data_fp).read_text())
    logging.info("Returning data...")
    return data


load_csv("s3://test/test.csv")  # Doesn't work
load_json("s3://test/test.csv")  # Works