Source code for cvxpy.expressions.constants.callback_param
"""
Copyright 2013 Steven Diamond
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 __future__ import annotations
from typing import Callable
from cvxpy.expressions.constants.parameter import Parameter
[docs]class CallbackParam(Parameter):
"""
A parameter whose value is derived from a callback function.
Enables writing replacing expression that would not be DPP
by a new parameter that automatically updates its value.
Example:
With p and q parameters, p * q is not DPP, but
pq = CallbackParameter(callback=lambda: p.value * q.value) is DPP.
This is useful when only p and q should be exposed
to the user, but pq is needed internally.
"""
def __init__(self, callback: Callable, shape: int | tuple[int, ...] = (), **kwargs) -> None:
"""
callback: function that returns the value of the parameter.
"""
self._callback = callback
super(CallbackParam, self).__init__(shape, **kwargs)
@property
def value(self):
"""Evaluate the callback to get the value.
"""
return self._validate_value(self._callback())
@value.setter
def value(self, _val):
raise NotImplementedError("Cannot set the value of a CallbackParam.")