# Source code for nnabla_rl.hook

```
# Copyright 2020,2021 Sony Corporation.
# Copyright 2021,2022,2023 Sony Group Corporation.
#
# 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.
from abc import ABCMeta, abstractmethod
from typing import TYPE_CHECKING
if TYPE_CHECKING:
from nnabla_rl.algorithm import Algorithm
[docs]class Hook(metaclass=ABCMeta):
"""Base class of hooks for Algorithm classes.
Hook is called at every 'timing' iterations during the training.
'timing' is specified at the beginning of the class instantiation.
"""
_timing: int = 1
def __init__(self, timing: int = 1000):
self._timing = timing
def __call__(self, algorithm: 'Algorithm'):
if algorithm.iteration_num % self._timing != 0:
return
self.on_hook_called(algorithm)
[docs] @abstractmethod
def on_hook_called(self, algorithm: 'Algorithm'):
"""Called every "timing" iteration which is set on Hook's instance
creation. Will run additional periodical operation (see each class'
documentation) during the training.
Args:
algorithm (:py:class:`Algorithm <nnabla_rl.algorithm.Algorithm>`):
Algorithm instance to perform additional operation.
"""
raise NotImplementedError
[docs] def setup(self, algorithm: 'Algorithm', total_iterations: int):
"""Called before the training starts.
Args:
algorithm (:py:class:`Algorithm <nnabla_rl.algorithm.Algorithm>`):
Algorithm instance to perform additional operation.
total_iteration (int): the number of total iterations.
"""
pass
[docs] def teardown(self, algorithm: 'Algorithm', total_iterations: int):
"""Called after the training ends.
Args:
algorithm (:py:class:`Algorithm <nnabla_rl.algorithm.Algorithm>`):
Algorithm instance to perform additional operation.
total_iteration (int): the number of total iterations.
"""
pass
```