From e9837f8346204fd47c102338e6d521f20dd246d5 Mon Sep 17 00:00:00 2001
From: daniel-rdt <daniel.ruedt@openenergytransition.org>
Date: Thu, 2 Jul 2026 17:25:19 +0200
Subject: [PATCH 1/2] fix: define inflow_t before branch so it is always
 assigned

---
 scripts/add_electricity.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scripts/add_electricity.py b/scripts/add_electricity.py
index 63f586501e..544fc66fdc 100755
--- a/scripts/add_electricity.py
+++ b/scripts/add_electricity.py
@@ -820,6 +820,7 @@ def attach_hydro(
     country = ppl["bus"].map(n.buses.country).rename("country")
 
     inflow_idx = ror.index.union(hydro.index)
+    inflow_t = pd.DataFrame()
     if not inflow_idx.empty:
         dist_key = ppl.loc[inflow_idx, "p_nom"].groupby(country).transform(normed)
 
@@ -853,7 +854,7 @@ def attach_hydro(
             capital_cost=costs.at["ror", "capital_cost"],
             weight=ror["p_nom"],
             p_max_pu=(
-                inflow_t[ror.index]  # pylint: disable=E0606
+                inflow_t[ror.index]
                 .divide(ror["p_nom"], axis=1)
                 .where(lambda df: df <= 1.0, other=1.0)
             ),

From 1587451ecd72aa0275f3735cb9cb97767ec55688 Mon Sep 17 00:00:00 2001
From: daniel-rdt <daniel.ruedt@openenergytransition.org>
Date: Thu, 2 Jul 2026 17:51:41 +0200
Subject: [PATCH 2/2] doc: add release note

---
 doc/release_notes.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/doc/release_notes.rst b/doc/release_notes.rst
index 05c2ce4933..9178b9dbee 100644
--- a/doc/release_notes.rst
+++ b/doc/release_notes.rst
@@ -35,6 +35,8 @@ Upcoming Open-TYNDP Release
 
 **Bugfixes and Compatibility**
 
+* Ensure ``inflow_t`` is always defined in ``attach_hydro``, resolving a pylint use-before-assignment issue (https://github.com/open-energy-transition/open-tyndp/pull/777).
+
 **Documentation**
 
 * Update benchmarking documentation tables and figures for v0.7.1 (https://github.com/open-energy-transition/open-tyndp/pull/711).