From 4dde524fb6f3032214b5e95ab0c3bf0cca7e39bc Mon Sep 17 00:00:00 2001
From: xuewc <wcxuemail@gmail.com>
Date: Wed, 27 Mar 2024 02:18:48 +0800
Subject: [PATCH] fix: informative exception

* more informative error message on loading type II spectrum
---
 src/elisa/data/ogip.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/elisa/data/ogip.py b/src/elisa/data/ogip.py
index 0ee2ba52..76e6b43c 100644
--- a/src/elisa/data/ogip.py
+++ b/src/elisa/data/ogip.py
@@ -691,7 +691,8 @@ def __init__(self, specfile: str, poisson: bool | None = None):
         # TODO: more robust way to detect a type II data
         # check if data is type II
         if not type_ii:
-            msg = f'row id must be provided for type II spectrum {specfile}'
+            msg = 'row id must be provided for type II spectrum, e.g., '
+            msg += f"'{specfile}{{1}}'"
 
             nchan = len(data)
             if int(header.get('DETCHANS', nchan)) != nchan: