Create explainer_probability.py

explainers/explainer_probability.py

@@ -0,0 +1,82 @@
+import re
+from models import ExplainerResult
+
+
+def explain_probability_question(text: str) -> ExplainerResult | None:
+    t = text.lower()
+
+    # ✅ STRONG detection
+    probability_signals = [
+        "probability",
+        "chance",
+        "odds",
+        "random",
+        "chosen at random",
+        "selected at random",
+        "picked at random",
+        "drawn",
+        "without replacement",
+        "with replacement",
+    ]
+
+    has_probability = any(p in t for p in probability_signals)
+
+    if not has_probability:
+        return None
+
+    givens = []
+    relationships = []
+    constraints = []
+    trap_notes = []
+
+    numbers = re.findall(r"\b\d+\b", t)
+
+    if numbers:
+        givens.append(f"Numbers mentioned: {', '.join(numbers[:5])}")
+    else:
+        givens.append("A situation involving possible outcomes is described")
+
+    if "without replacement" in t:
+        relationships.append("The probabilities change after each selection")
+        constraints.append("The total number of items decreases after each draw")
+
+    if "with replacement" in t:
+        relationships.append("The probabilities stay the same for each selection")
+
+    if "at least" in t:
+        relationships.append("This may require using the complement (1 - probability of the opposite event)")
+
+    if "both" in t or "and" in t:
+        relationships.append("You may need to combine probabilities of multiple events occurring together")
+
+    if "or" in t:
+        relationships.append("You may need to consider multiple possible favorable cases")
+
+    # default structure
+    relationships.append("Probability = favorable outcomes ÷ total possible outcomes")
+
+    asks_for = "the probability of a specific event occurring"
+
+    trap_notes.extend([
+        "Make sure you correctly identify the total number of possible outcomes",
+        "Check whether events are independent or dependent",
+        "Watch for 'at least' — often easier to use the complement",
+        "Be careful not to double count outcomes",
+    ])
+
+    return ExplainerResult(
+        understood=True,
+        topic="probability",
+        asks_for=asks_for,
+        givens=givens,
+        constraints=constraints,
+        relationships=relationships,
+        needed_concepts=[
+            "favorable vs total outcomes",
+            "independent vs dependent events",
+            "complement rule",
+        ],
+        trap_notes=trap_notes,
+        strategy_hint="Start by identifying all possible outcomes, then count how many satisfy the condition.",
+        plain_english="The question is asking you to work out how likely an event is by comparing favorable outcomes to all possible outcomes.",
+    )