90 lines
2.8 KiB
Plaintext
90 lines
2.8 KiB
Plaintext
This rule raises an issue when an attribute ending with ``++_++`` is set in the ``++__init__++`` method of a class inheriting from
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Scikit-Learn `BaseEstimator`
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== Why is this an issue?
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On a Scikit-Learn estimator, attributes that have a trailing underscore represent attributes that are estimated.
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These attributes have to be set in the fit method. Their presence is used to verify if an estimator has been fitted.
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[source,python]
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----
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from sklearn.neighbors import KNeighborsClassifier
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X = [[0], [1], [2], [3]]
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y = [0, 0, 1, 1]
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knn = KNeighborsClassifier(n_neighbors=1)
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knn.fit(X, y)
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knn.n_samples_fit_
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----
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In the example above the attributes of the `KNeighborsClassifier`, ``++n_samples_fit_++``
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is set only after the estimator's `fit` method is called. Calling ``++n_samples_fit_++`` before the estimator is fitted
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would raise an `AttributeError` exception.
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When implementing a custom estimator by subclassing Scikit-Learn's `BaseEstimator`,
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it is important to follow the above convention and not set attributes with a trailing underscore inside the ``++__init__++`` method.
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== How to fix it
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To fix this issue, move the attributes with a trailing underscore from the ``++__init__++`` method to the `fit` method.
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=== Code examples
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==== Noncompliant code example
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[source,python,diff-id=1,diff-type=noncompliant]
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----
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from sklearn.base import BaseEstimator
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class MyEstimator(BaseEstimator):
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def __init__(self):
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self.estimated_attribute_ = None # Noncompliant: an estimated attribute is set in the __init__ method.
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----
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==== Compliant solution
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[source,python,diff-id=1,diff-type=compliant]
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----
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from sklearn.base import BaseEstimator
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class MyEstimator(BaseEstimator):
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def fit(self, X, y):
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self.estimated_attribute_ = some_estimation(X) # Compliant
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----
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== Resources
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=== Documentation
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* Scikit-Learn documentation - https://scikit-learn.org/stable/developers/develop.html#parameters-and-init[Parameters and init]
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ifdef::env-github,rspecator-view[]
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(visible only on this page)
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== Implementation specification
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Verify that subclasses of BaseEstimator do not have attributes with a trailing underscore in the __init__ method.
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Verify that inherited alongside BaseEstimator do not have attributes with a trailing underscore in the __init__ method.
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=== Message
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Primary : Move this estimated attribute inside the `fit` method.
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Secondary: this attributes is used in this estimator (in the case of mixins)
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=== Issue location
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Primary : name of the attribute
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Secondary : the name of the estimator subclassing the mixin and the BaseEstimator
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=== Quickfix
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Possible quickfix if the `fit` method does not exist. (Add the fit method with the estimated attribute) and delete the estimated attributes
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from the __init__ method. This is only possible in an estimator directly subclassing BaseEstimator.
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endif::env-github,rspecator-view[]
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