From 70bc8f338919aa6180d8bac8dda74a54fd04e1e6 Mon Sep 17 00:00:00 2001
From: Sanjay Santhanam <51058514+Sanjays2402@users.noreply.github.com>
Date: Sun, 19 Jul 2026 14:53:28 -0700
Subject: [PATCH] fix: preserve totals when splitting rounded values

Adjust the final allocation by the rounding remainder so proportional splits add back up to the requested total. Add a regression for three equal weights.
---
 percentify/stats.py | 3 +++
 tests/test_stats.py | 4 +++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/percentify/stats.py b/percentify/stats.py
index 158f951..8741c31 100644
--- a/percentify/stats.py
+++ b/percentify/stats.py
@@ -892,6 +892,9 @@ def split(total, weights, decimals: Optional[int] = 2):
     shares = w.astype(float) / weight_sum * float(total)
     if decimals is not None:
         shares = shares.round(decimals)
+        remainder = round(float(total), decimals) - float(shares.sum())
+        if remainder:
+            shares.iloc[-1] = round(shares.iloc[-1] + remainder, decimals)
     return shares if is_series else shares.tolist()
 
 
diff --git a/tests/test_stats.py b/tests/test_stats.py
index 7ac2e01..2b81393 100644
--- a/tests/test_stats.py
+++ b/tests/test_stats.py
@@ -609,7 +609,9 @@ def test_split_list():
 
 
 def test_split_equal():
-    assert split(100, [1, 1, 1]) == [pytest.approx(33.33)] * 3
+    result = split(100, [1, 1, 1])
+    assert result == [33.33, 33.33, 33.34]
+    assert sum(result) == 100
 
 
 def test_split_series_returns_series():