lightning/tests/helpers/dataloaders.py

# Copyright The PyTorch Lightning team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Custom dataloaders for testing."""


class CustomInfDataloader:
    def __init__(self, dataloader):
        self.dataloader = dataloader
        self.iter = iter(dataloader)
        self.count = 0
        self.dataloader.num_workers = 0  # reduce chance for hanging pytest

    def __iter__(self):
        self.count = 0
        return self

    def __next__(self):
        if self.count >= 50:
            raise StopIteration
        self.count = self.count + 1
        try:
            return next(self.iter)
        except StopIteration:
            self.iter = iter(self.dataloader)
            return next(self.iter)


class CustomNotImplementedErrorDataloader(CustomInfDataloader):
    def __len__(self):
        """raise NotImplementedError."""
        raise NotImplementedError

    def __next__(self):
        if self.count >= 2:
            raise StopIteration
        self.count = self.count + 1
        try:
            return next(self.iter)
        except StopIteration:
            self.iter = iter(self.dataloader)
            return next(self.iter)