[UPDATE] float output to match short time delta

Considering the variation of days between two dates, this function provides the user with a floating-point representation of the month difference, allowing for a more precise measurement of time intervals.

src/month_diff.rs

@@ -1,4 +1,3 @@
-use chrono::Datelike;
 use polars::prelude::*;
 use pyo3_polars::derive::polars_expr;
 
@@ -14,14 +13,16 @@ pub fn month_diff(
     }
 
 
-    let month_diff: Int32Chunked = start_dates.as_date_iter().zip(end_dates.as_date_iter()).map(
+    let month_diff: Float32Chunked = start_dates.as_date_iter().zip(end_dates.as_date_iter()).map(
         |(s_arr, e_arr)| {
             s_arr.zip(e_arr).map(
                 |(left, right)| {
                     {
-                        let month_diff = right.month() as i32 - left.month() as i32;
-                        let year_diff = (right.year() - left.year()) * 12;
-                        month_diff + year_diff
+                        let duration_delta = right.signed_duration_since(left);
+                        let days_delta = duration_delta.num_days() as f32;
+                        let year_fraction = days_delta / 365.25;
+                        let month_diff = year_fraction * 12.;
+                        month_diff
                     }
                 }
             )

tests/test_month_diff.py

@@ -35,7 +35,8 @@ def test_month_diff():
         .to_list()
     )
 
-    assert [13, 2, 0, -12] == month_diff_list, (
+    expected_month_diff = [13.01026725769043, 2.0041067600250244, 0.0, -11.99178695678711]
+    assert expected_month_diff == month_diff_list, (
         "The month difference list did not match the expected values.\n"
         "Please check the function: 'month_diff.rs' for discrepancies."
     )