Source code for diffprivlib.mechanisms.transforms.base

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"""
Core utilities for DP transformers.
"""
from diffprivlib.mechanisms.base import DPMachine


[docs] class DPTransformer(DPMachine): """ Base class for DP transformers. DP Transformers are simple wrappers for DP Mechanisms to allow mechanisms to be used with data types and structures outside their scope. A :class:`.DPTransformer` must be initiated with a :class:`.DPMachine` (either another :class:`.DPTransformer`, or a :class:`.DPMechanism`). This allows many instances of :class:`.DPTransformer` to be chained together, but the chain must terminate with a :class:`.DPMechanism`. """ def __init__(self, parent): if not isinstance(parent, DPMachine): raise TypeError("Data transformer must take a DPMachine as input") self.parent = parent
[docs] def pre_transform(self, value): """Performs no transformation on the input data, and is ingested by the mechanism as-is. Parameters ---------- value : float or string Input value to be transformed. Returns ------- float or string Transformed input value """ return value
[docs] def post_transform(self, value): """Performs no transformation on the output of the mechanism, and is returned as-is. Parameters ---------- value : float or string Mechanism output to be transformed. Returns ------- float or string Transformed output value. """ return value
[docs] def randomise(self, value): """ Randomise the given value using the :class:`.DPMachine`. Parameters ---------- value : float or string Value to be randomised. Returns ------- float or string Randomised value, same type as `value`. """ transformed_value = self.pre_transform(value) noisy_value = self.parent.randomise(transformed_value) output_value = self.post_transform(noisy_value) return output_value