From 9048af482fdd6cfbe7202efa5561fe6f078c7734 Mon Sep 17 00:00:00 2001
From: Koen van Greevenbroek
 <74298901+koen-van-greevenbroek@users.noreply.github.com>
Date: Wed, 10 Mar 2021 18:16:09 +0100
Subject: [PATCH] Add a check to fix KeyError (#220) (#228)

In some cases, in networks with DC links, a non-existing column would
be referenced in an empty Dataframe. This commit adds a check for this
case.

Co-authored-by: Koen van Greevenbroek <koen@vesoldo.com>
---
 scripts/add_electricity.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/scripts/add_electricity.py b/scripts/add_electricity.py
index 8fc8ad5c..e16e1766 100755
--- a/scripts/add_electricity.py
+++ b/scripts/add_electricity.py
@@ -245,6 +245,11 @@ def update_transmission_costs(n, costs, length_factor=1.0, simple_hvdc_costs=Fal
     if n.links.empty: return
 
     dc_b = n.links.carrier == 'DC'
+
+    # If there are no dc links, then the 'underwater_fraction' column
+    # may be missing. Therefore we have to return here.
+    if n.links.loc[dc_b].empty: return
+
     if simple_hvdc_costs:
         costs = (n.links.loc[dc_b, 'length'] * length_factor *
                  costs.at['HVDC overhead', 'capital_cost'])