init commit

features.py

@@ -0,0 +1,47 @@
+import math
+import re
+from collections import Counter
+
+import numpy as np
+
+
+def shannon_entropy(s: str) -> float:
+    if not s:
+        return 0.0
+    counts = Counter(s)
+    length = len(s)
+    return -sum((c / length) * math.log2(c / length) for c in counts.values())
+
+
+def special_char_ratio(s: str) -> float:
+    if not s:
+        return 0.0
+    specials = sum(1 for ch in s if not ch.isalnum() and not ch.isspace())
+    return specials / len(s)
+
+
+def digit_ratio(s: str) -> float:
+    if not s:
+        return 0.0
+    return sum(ch.isdigit() for ch in s) / len(s)
+
+
+def keyword_hit_count(s: str, keywords) -> int:
+    low = s.lower()
+    return sum(1 for kw in keywords if kw in low)
+
+
+def handcrafted_feature_matrix(texts, keywords):
+    rows = []
+    for t in texts:
+        rows.append([
+            len(t),
+            shannon_entropy(t),
+            special_char_ratio(t),
+            digit_ratio(t),
+            keyword_hit_count(t, keywords),
+        ])
+    return np.array(rows, dtype=float)
+
+
+FEATURE_NAMES = ["length", "entropy", "special_char_ratio", "digit_ratio", "keyword_hits"]