Removed addition of period from wrap_lons.

Updated affected tests using assertArrayAllClose following #3993.

docs/src/whatsnew/latest.rst

@@ -199,10 +199,16 @@ This document explains the changes made to Iris for this release
 #. `@rcomer`_ modified a NetCDF saver test to prevent it triggering a numpy
    deprecation warning.  (:issue:`4374`, :pull:`4376`)
 
+#. `@akuhnregnier`_ removed addition of period from
+   :func:`~iris.analysis.cartography.wrap_lons` and updated affected tests
+   using assertArrayAllClose following :issue:`3993`.
+   (:pull:`3994`)
+
 .. comment
     Whatsnew author names (@github name) in alphabetical order. Note that,
     core dev names are automatically included by the common_links.inc:
 
+.. _@akuhnregnier: https://github.com/akuhnregnier
 .. _@bsherratt: https://github.com/bsherratt
 .. _@larsbarring: https://github.com/larsbarring
 .. _@pdearnshaw: https://github.com/pdearnshaw

lib/iris/analysis/cartography.py

@@ -70,7 +70,7 @@ def wrap_lons(lons, base, period):
     # It is important to use 64bit floating precision when changing a floats
     # numbers range.
     lons = lons.astype(np.float64)
-    return ((lons - base + period * 2) % period) + base
+    return ((lons - base) % period) + base
 
 
 def unrotate_pole(rotated_lons, rotated_lats, pole_lon, pole_lat):

lib/iris/tests/unit/cube/test_Cube.py

@@ -1662,11 +1662,9 @@ def test_wrap_radians(self):
         cube = create_cube(0, 360)
         cube.coord("longitude").convert_units("radians")
         result = cube.intersection(longitude=(-1, 0.5))
-        self.assertEqual(
-            result.coord("longitude").points[0], -0.99483767363676634
-        )
-        self.assertEqual(
-            result.coord("longitude").points[-1], 0.48869219055841207
+        self.assertArrayAllClose(
+            result.coord("longitude").points,
+            np.arange(-57, 29) * np.pi / 180
         )
         self.assertEqual(result.data[0, 0, 0], 303)
         self.assertEqual(result.data[0, 0, -1], 28)