From 36f5786ebcc1c26bc403c5ad34ab9a2b05b99190 Mon Sep 17 00:00:00 2001
From: David Hassell <david.hassell@ncas.ac.uk>
Date: Tue, 20 Feb 2024 17:54:19 +0000
Subject: [PATCH] dev

---
 cfdm/field.py | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/cfdm/field.py b/cfdm/field.py
index 92ec2eb30..e16e02d90 100644
--- a/cfdm/field.py
+++ b/cfdm/field.py
@@ -2178,6 +2178,8 @@ def insert_dimension(
         (19, 73, 1, 96)
         >>> f.data.shape
         (19, 73, 1, 96)
+        >>> f.insert_dimension(None, 1).data.shape
+        (19, 1, 73, 1, 96)
 
         """
         f = _inplace_enabled_define_and_cleanup(self)
@@ -2185,11 +2187,11 @@ def insert_dimension(
         if axis is None:
             axis = f.set_construct(self._DomainAxis(1))
         else:
-            domain_axis = f.domain_axes(todict=True).get(axis)
-            if domain_axis is None:
-                raise ValueError(
-                    f"Can't insert non-existent domain axis: {axis}"
-                )
+            axis, domain_axis = f.domain_axis(
+                axis,
+                item=True,
+                default=ValueError("Can't identify a unique axis to insert"),
+            )
 
             if domain_axis.get_size() != 1:
                 raise ValueError(