CODEWITHSUNDEEP
python
nwpuxhld
nwpuxhld

Reputation: 85

Python, How to use the @ in class method

I try to use the @ in the class method. like this

class Dataset:
  @parse_func
  def get_next_batch(self):
      return self.generator.__next__()

and the parse function like this:

def parse_func(load_batch):
  def wrapper(**para):
    batch_files_path, batch_masks_path, batch_label = load_batch(**para)
    batch_images = []
    batch_masks = []
    for (file_path, mask_path) in zip(batch_files_path, batch_masks_path):
        image = cv2.imread(file_path)
        mask = cv2.imread(mask_path)
        batch_images.append(image)
        batch_masks.append(mask)
    return np.asarray(batch_images, np.float32), np.asarray(batch_masks, np.uint8), batch_label

  return wrapper

However, when I call dataset.get_next_batch(), it will raise a exception as followed.

Traceback (most recent call last): TypeError: wrapper() takes exactly 0 arguments (1 given)

Do you know why raise this error and any solution? Thank you very much!

Upvotes: 0

Views: 90

Answers (2)

blue note
blue note

Reputation: 29071

The function wrapper(**kwargs) accepts named arguments only. However, in instance methods, the self is automatically passed as the first positional argument. Since your method does not accept positional arguments, it fails.

You could edit to wrapper(self, **kwargs) or, more general wrapper(*args, **kwargs). However, the way you are using it, it is not clear what those arguments are.

Upvotes: 1

tianhua liao
tianhua liao

Reputation: 675

Just simply change 

def parse_func(load_batch):
  def wrapper(*para):
    batch_files_path, batch_masks_path, batch_label = load_batch(*para)
    batch_images = []
    batch_masks = []
    for (file_path, mask_path) in zip(batch_files_path, batch_masks_path):
        image = cv2.imread(file_path)
        mask = cv2.imread(mask_path)
        batch_images.append(image)
        batch_masks.append(mask)
    return np.asarray(batch_images, np.float32), np.asarray(batch_masks, np.uint8), batch_label

  return wrapper()

@ symbol mean a decorator function. Here, it means parse_func(get_next_batch). So if the wrapper using the keyword params (**para), you just want to pass some params to the wrapper but you don't actually except for the self args. So here I replace the params to positional params *para.

Upvotes: 0

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