Configure numpy printoptions legacy (#6557)

* Configure numpy printoptions legacy

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: bjlittle

lib/iris/cube.py

@@ -28,6 +28,7 @@
 import dask.array as da
 import numpy as np
 import numpy.ma as ma
+from packaging.version import Version
 
 import iris._constraints
 from iris._data_manager import DataManager
@@ -60,6 +61,15 @@
 __all__ = ["Cube", "CubeAttrsDict", "CubeList"]
 
 
+# Determine the numpy printoptions legacy setting.
+_NP_VERSION = Version(np.__version__)
+_NP_LEGACY_VERSION = Version("2.2")
+NP_PRINTOPTIONS_LEGACY = (
+    str(_NP_LEGACY_VERSION)
+    if Version(f"{_NP_VERSION.major}.{_NP_VERSION.minor}") > _NP_LEGACY_VERSION
+    else False
+)
+
 # The XML namespace to use for CubeML documents
 XML_NAMESPACE_URI = "urn:x-iris:cubeml-0.2"
 
@@ -162,7 +172,7 @@ def insert(self, index, cube):
 
     def xml(self, checksum=False, order=True, byteorder=True):
         """Return a string of the XML that this list of cubes represents."""
-        with np.printoptions(legacy="2.2"):
+        with np.printoptions(legacy=NP_PRINTOPTIONS_LEGACY):
             doc = Document()
             cubes_xml_element = doc.createElement("cubes")
             cubes_xml_element.setAttribute("xmlns", XML_NAMESPACE_URI)
@@ -3865,7 +3875,7 @@ def xml(
         byteorder: bool = True,
     ) -> str:
         """Return a fully valid CubeML string representation of the Cube."""
-        with np.printoptions(legacy="2.2"):
+        with np.printoptions(legacy=NP_PRINTOPTIONS_LEGACY):
             doc = Document()
 
             cube_xml_element = self._xml_element(

lib/iris/tests/test_pp_module.py

@@ -12,6 +12,7 @@
 from numpy.testing import assert_array_equal
 import pytest
 
+from iris.cube import NP_PRINTOPTIONS_LEGACY
 import iris.fileformats.pp as pp
 from iris.tests import _shared_utils
 
@@ -64,7 +65,7 @@ def check_pp(self, pp_fields, reference_filename):
         for pp_field in pp_fields:
             pp_field.data
 
-        with np.printoptions(legacy="2.2"):
+        with np.printoptions(legacy=NP_PRINTOPTIONS_LEGACY):
             test_string = str(pp_fields)
         reference_path = _shared_utils.get_result_path(reference_filename)
         if os.path.isfile(reference_path):