mindspore.dataset.SequentialSampler

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

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()[source]

Parse the sampler.

parse_child()

Parse the child sampler.

parse_child_for_minddataset()

Parse the child sampler for MindRecord.

parse_for_minddataset()[source]

Parse the sampler for MindRecord.