update document of paddle.vision.dataset, test=document (#30414)

* update document of paddle.vision.dataset, test=document

* update document of paddle.vision.dataset, test=document

python/paddle/vision/datasets/cifar.py

@@ -47,11 +47,10 @@ class Cifar10(Dataset):
 
     Args:
         data_file(str): path to data file, can be set None if
-            :attr:`download` is True. Default None
+            :attr:`download` is True. Default None, default data path: ~/.cache/paddle/dataset/cifar
         mode(str): 'train', 'test' mode. Default 'train'.
-        transform(callable): transform to perform on image, None for on transform.
-        download(bool): whether to download dataset automatically if
-            :attr:`data_file` is not set. Default True
+        transform(callable): transform to perform on image, None for no transform.
+        download(bool): download dataset automatically if :attr:`data_file` is None. Default True
         backend(str, optional): Specifies which type of image to be returned: 
             PIL.Image or numpy.ndarray. Should be one of {'pil', 'cv2'}. 
             If this option is not set, will get backend from ``paddle.vsion.get_image_backend`` ,
@@ -180,11 +179,10 @@ class Cifar100(Cifar10):
 
     Args:
         data_file(str): path to data file, can be set None if
-            :attr:`download` is True. Default None
+            :attr:`download` is True. Default None, default data path: ~/.cache/paddle/dataset/cifar
         mode(str): 'train', 'test' mode. Default 'train'.
-        transform(callable): transform to perform on image, None for on transform.
-        download(bool): whether to download dataset automatically if
-            :attr:`data_file` is not set. Default True
+        transform(callable): transform to perform on image, None for no transform.
+        download(bool): download dataset automatically if :attr:`data_file` is None. Default True
         backend(str, optional): Specifies which type of image to be returned: 
             PIL.Image or numpy.ndarray. Should be one of {'pil', 'cv2'}. 
             If this option is not set, will get backend from ``paddle.vsion.get_image_backend`` ,

python/paddle/vision/datasets/flowers.py

@@ -47,15 +47,14 @@ class Flowers(Dataset):
 
     Args:
         data_file(str): path to data file, can be set None if
-            :attr:`download` is True. Default None
+            :attr:`download` is True. Default None, default data path: ~/.cache/paddle/dataset/flowers/
         label_file(str): path to label file, can be set None if
-            :attr:`download` is True. Default None
+            :attr:`download` is True. Default None, default data path: ~/.cache/paddle/dataset/flowers/
         setid_file(str): path to subset index file, can be set
             None if :attr:`download` is True. Default None
         mode(str): 'train', 'valid' or 'test' mode. Default 'train'.
-        transform(callable): transform to perform on image, None for on transform.
-        download(bool): whether to download dataset automatically if
-            :attr:`data_file` is not set. Default True
+        transform(callable): transform to perform on image, None for no transform.
+        download(bool): download dataset automatically if :attr:`data_file` is None. Default True
         backend(str, optional): Specifies which type of image to be returned: 
             PIL.Image or numpy.ndarray. Should be one of {'pil', 'cv2'}. 
             If this option is not set, will get backend from ``paddle.vsion.get_image_backend`` ,

python/paddle/vision/datasets/folder.py

@@ -111,6 +111,9 @@ class DatasetFolder(Dataset):
                 return data_dir
 
             temp_dir = make_fake_dir()
+            # temp_dir is root dir
+            # temp_dir/class_1/img1_1.jpg
+            # temp_dir/class_2/img2_1.jpg
             data_folder = DatasetFolder(temp_dir)
 
             for items in data_folder:

python/paddle/vision/datasets/mnist.py

@@ -33,11 +33,11 @@ class MNIST(Dataset):
 
     Args:
         image_path(str): path to image file, can be set None if
-            :attr:`download` is True. Default None
+            :attr:`download` is True. Default None, default data path: ~/.cache/paddle/dataset/mnist
         label_path(str): path to label file, can be set None if
-            :attr:`download` is True. Default None
+            :attr:`download` is True. Default None, default data path: ~/.cache/paddle/dataset/mnist
         mode(str): 'train' or 'test' mode. Default 'train'.
-        download(bool): whether to download dataset automatically if
+        download(bool): download dataset automatically if
             :attr:`image_path` :attr:`label_path` is not set. Default True
         backend(str, optional): Specifies which type of image to be returned: 
             PIL.Image or numpy.ndarray. Should be one of {'pil', 'cv2'}. 

python/paddle/vision/datasets/voc2012.py

@@ -46,10 +46,9 @@ class VOC2012(Dataset):
 
     Args:
         data_file(str): path to data file, can be set None if
-            :attr:`download` is True. Default None
+            :attr:`download` is True. Default None,  default data path: ~/.cache/paddle/dataset/voc2012
         mode(str): 'train', 'valid' or 'test' mode. Default 'train'.
-        download(bool): whether to download dataset automatically if
-            :attr:`data_file` is not set. Default True
+        download(bool): download dataset automatically if :attr:`data_file` is None. Default True
         backend(str, optional): Specifies which type of image to be returned: 
             PIL.Image or numpy.ndarray. Should be one of {'pil', 'cv2'}. 
             If this option is not set, will get backend from ``paddle.vsion.get_image_backend`` ,