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import os |
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import io |
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import json |
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import base64 |
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from typing import Dict, Optional |
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import shap |
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import pandas as pd |
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import matplotlib.pyplot as plt |
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import joblib |
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from huggingface_hub import hf_hub_download |
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from utils.config import AppConfig |
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from utils.tracing import Tracer |
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class ExplainTool: |
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""" |
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Generates global SHAP visualizations for a sample of rows (CPU-friendly). |
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""" |
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def __init__(self, cfg: AppConfig, tracer: Tracer): |
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self.cfg = cfg |
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self.tracer = tracer |
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self._model = None |
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self._feature_order = None |
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def _ensure_model(self): |
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if self._model is not None: |
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return |
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token = os.getenv("HF_TOKEN") |
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repo = self.cfg.hf_model_repo |
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model_path = hf_hub_download(repo_id=repo, filename="model.pkl", token=token) |
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self._model = joblib.load(model_path) |
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try: |
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meta_path = hf_hub_download(repo_id=repo, filename="feature_metadata.json", token=token) |
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with open(meta_path, "r", encoding="utf-8") as f: |
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meta = json.load(f) or {} |
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self._feature_order = meta.get("feature_order") |
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except Exception: |
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self._feature_order = None |
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@staticmethod |
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def _to_data_uri(fig) -> str: |
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buf = io.BytesIO() |
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fig.savefig(buf, format="png", bbox_inches="tight", dpi=150) |
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plt.close(fig) |
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buf.seek(0) |
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return "data:image/png;base64," + base64.b64encode(buf.read()).decode() |
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def run(self, df: Optional[pd.DataFrame]) -> Dict[str, str]: |
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self._ensure_model() |
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if df is None or len(df) == 0: |
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return {} |
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if self._feature_order: |
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cols = [c for c in self._feature_order if c in df.columns] |
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X = df[cols].copy() |
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else: |
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X = df.copy() |
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n = min(len(X), 500) |
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sample = X.sample(n, random_state=42) if len(X) > n else X |
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explainer = shap.Explainer(self._model, sample) |
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sv = explainer(sample) |
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fig_bar = plt.figure() |
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shap.plots.bar(sv, show=False) |
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bar_uri = self._to_data_uri(fig_bar) |
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fig_bee = plt.figure() |
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shap.plots.beeswarm(sv, show=False) |
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bee_uri = self._to_data_uri(fig_bee) |
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try: |
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self.tracer.trace_event("explain", {"rows": int(n)}) |
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except Exception: |
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pass |
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return {"global_bar": bar_uri, "beeswarm": bee_uri} |
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