51 lines
1.7 KiB
Python
51 lines
1.7 KiB
Python
import numpy as np
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from sklearn.base import BaseEstimator, ClassifierMixin, TransformerMixin
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from sklearn.feature_extraction import DictVectorizer
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from sklearn.linear_model import LogisticRegression
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from sklearn.pipeline import Pipeline
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class FeatureExtractor(BaseEstimator, TransformerMixin):
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def __init__(self, extract_fn):
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self.extract_fn = extract_fn
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def fit(self, X, y=None):
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return self
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def transform(self, X):
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return [self.extract_fn(msg) for msg in X]
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class FeatureClassifier(BaseEstimator, ClassifierMixin):
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def __init__(self, C=1.0):
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self.C = C
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def fit(self, X, y):
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self._pipeline = Pipeline([
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("features", FeatureExtractor(self.extract_features)),
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("vectorizer", DictVectorizer()),
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("classifier", LogisticRegression(C=self.C, max_iter=1000)),
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])
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y_binary = (np.array(y) == "spam").astype(int)
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self._pipeline.fit(X, y_binary)
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return self
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def predict(self, X):
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y_binary = self._pipeline.predict(X)
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return np.where(y_binary == 1, "spam", "ham")
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def extract_features(self, message):
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return {
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"contains_free": int("free" in message.lower()),
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"num_exclamations": message.count("!"),
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"length": len(message),
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}
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def feature_weights(self, top_n=10):
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vectorizer = self._pipeline.named_steps["vectorizer"]
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classifier = self._pipeline.named_steps["classifier"]
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names = vectorizer.get_feature_names_out()
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weights = classifier.coef_[0]
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pairs = sorted(zip(names, weights), key=lambda x: abs(x[1]), reverse=True)
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return pairs[:top_n]
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