Add an extra pandas.sort_values() to get an deterministic result of ordered strongly meshed buses. (PyPSA#1174)

* Update common.py

add an extra pandas.sort_values() to get an deterministic result of ordered strongly meshed buses.

* Update release-notes.rst

add entry in the release-notes.rst

* Update doc/references/release-notes.rst

---------

Co-authored-by: Lukas Trippe <[email protected]>

Author: JN-TBW-EX

doc/references/release-notes.rst

@@ -29,6 +29,10 @@ Features
   expression (regex), enabling more flexible filtering options. 
   (https://github.com/PyPSA/PyPSA/pull/1155)
 
+Minor improvements
+------------------
+
+* Ensuring that the created lp/mps file is deterministic by sorting the strongly meshed buses. (https://github.com/PyPSA/PyPSA/pull/1174)
 
 `v0.33.2 <https://github.com/PyPSA/PyPSA/releases/tag/v0.33.2>`__ (12th March 2025)
 =======================================================================================

pypsa/optimization/common.py

@@ -66,4 +66,6 @@ def get_strongly_meshed_buses(n: Network, threshold: int = 45) -> pd.Series:
     )
     all_buses = all_buses[all_buses != ""]
     counts = all_buses.value_counts()
-    return counts.index[counts > threshold].rename("Bus-meshed")
+    results = counts.index[counts > threshold].rename("Bus-meshed")
+    results = results.sort_values()
+    return results