mindspore.dataset.SequentialSampler

class mindspore.dataset.SequentialSampler(start_index=None, num_samples=None)

Samples the dataset elements sequentially that is equivalent to not using a sampler.

Parameters

• start_index (int, optional) – Index to start sampling at. (default=None, start at first ID)

• num_samples (int, optional) – Number of elements to sample (default=None, which means sample all elements).

Examples

>>> # creates a SequentialSampler
>>> sampler = ds.SequentialSampler()
>>> dataset = ds.ImageFolderDataset(image_folder_dataset_dir,
...                                 num_parallel_workers=8,
...                                 sampler=sampler)

Raises

• TypeError – If start_index is not an integer value.

• TypeError – If num_samples is not an integer value.

• RuntimeError – If start_index is a negative value.

• ValueError – If num_samples is a negative value.

add_child(sampler)

Add a sub-sampler for given sampler. The sub-sampler will receive all data from the output of parent sampler and apply its sample logic to return new samples.

Parameters

sampler (Sampler) – Object used to choose samples from the dataset. Only builtin samplers(DistributedSampler, PKSampler, RandomSampler, SequentialSampler, SubsetRandomSampler, WeightedRandomSampler) are supported.

Examples

>>> sampler = ds.SequentialSampler(start_index=0, num_samples=3)
>>> sampler.add_child(ds.RandomSampler(num_samples=2))
>>> dataset = ds.Cifar10Dataset(cifar10_dataset_dir, sampler=sampler)

get_child()

Get the child sampler.

get_num_samples()

All samplers can contain a numeric num_samples value (or it can be set to None). A child sampler can exist or be None. If a child sampler exists, then the child sampler count can be a numeric value or None. These conditions impact the resultant sampler count that is used. The following table shows the possible results from calling this function.

child sampler	num_samples	child_samples	result
T	x	y	min(x, y)
T	x	None	x
T	None	y	y
T	None	None	None
None	x	n/a	x
None	None	n/a	None

Returns

int, the number of samples, or None.

parse()

Parse the sampler.

parse_child()

Parse the child sampler.

parse_child_for_minddataset()

Parse the child sampler for MindRecord.

parse_for_minddataset()

Parse the sampler for MindRecord.