From b634b2a9731aca4ad6cf65d9782c9b39859728dd Mon Sep 17 00:00:00 2001
From: "Marcel R." <github.riga@icloud.com>
Date: Wed, 7 Aug 2024 13:39:45 +0200
Subject: [PATCH] Add getitem support.

---
 scinum/__init__.py   | 15 ++++++++++++++-
 tests/test_number.py |  8 ++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/scinum/__init__.py b/scinum/__init__.py
index 21a5d8e..9d255a9 100644
--- a/scinum/__init__.py
+++ b/scinum/__init__.py
@@ -840,7 +840,7 @@ def copy(
         if uncertainties is None:
             uncertainties = self.uncertainties
 
-        return self.__class__(nominal, uncertainties=uncertainties)
+        return self.__class__(nominal, uncertainties=uncertainties, **self._init_kwargs())  # type: ignore[arg-type] # noqa
 
     def get(
         self,
@@ -1113,6 +1113,19 @@ def __call__(
         # shorthand for get
         return self.get(direction=direction, names=names, unc=unc, factor=factor)
 
+    def __getitem__(self, key: int | slice) -> Number:
+        if not self.is_numpy:
+            raise TypeError("cannot index non-NumPy number")
+
+        return self.__class__(
+            self.nominal[key],
+            uncertainties={
+                name: (up[key], down[key])
+                for name, (up, down) in self.uncertainties.items()
+            },
+            **self._init_kwargs(),  # type: ignore[arg-type]
+        )
+
     def __float__(self) -> OutValueType:
         # extract nominal value
         return self.nominal
diff --git a/tests/test_number.py b/tests/test_number.py
index 4a073f9..4fe687d 100644
--- a/tests/test_number.py
+++ b/tests/test_number.py
@@ -150,6 +150,14 @@ def test_copy_numpy(self) -> None:
         self.assertEqual(len(num.uncertainties), 1)
         self.assertEqual(num.u(direction=UP).shape, (3,))
 
+    @if_numpy
+    def test_getitem_numpy(self) -> None:
+        num = Number(np.array([5, 27, 42]), 5)[1:]
+
+        self.assertEqual(tuple(num.nominal), (27, 42))
+        self.assertEqual(len(num.uncertainties), 1)
+        self.assertEqual(tuple(num.uncertainties["default"][0]), (5, 5))
+
     def test_string_formats(self) -> None:
         self.assertEqual(len(self.num.str()), 102)
         self.assertEqual(len(self.num.str("%.3f")), 126)