From ef1c5dba3752f9308685e2ce57cb017e54e719e1 Mon Sep 17 00:00:00 2001
From: Jakob Gamper <97gamjak@gmail.com>
Date: Wed, 5 Jun 2024 01:16:32 +0200
Subject: [PATCH] fix: read_trajectory with constant topology did actually not
 use a constant topology approach

---
 PQAnalysis/io/traj_file/frame_reader.py      | 4 +++-
 PQAnalysis/io/traj_file/trajectory_reader.py | 4 ++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/PQAnalysis/io/traj_file/frame_reader.py b/PQAnalysis/io/traj_file/frame_reader.py
index 1a615ce7..ebdb00d3 100644
--- a/PQAnalysis/io/traj_file/frame_reader.py
+++ b/PQAnalysis/io/traj_file/frame_reader.py
@@ -251,7 +251,9 @@ def _check_qmcfc(
         return value, atoms
 
     def _get_topology(
-        self, atoms: List[str], topology: Topology | None
+        self,
+        atoms: List[str],
+        topology: Topology | None,
     ) -> Topology:
         """
         Returns the topology of the frame.
diff --git a/PQAnalysis/io/traj_file/trajectory_reader.py b/PQAnalysis/io/traj_file/trajectory_reader.py
index bc3ddb83..e35d7615 100644
--- a/PQAnalysis/io/traj_file/trajectory_reader.py
+++ b/PQAnalysis/io/traj_file/trajectory_reader.py
@@ -251,7 +251,7 @@ def frame_generator(
                             # then increment the frame index
                             frame_index += 1
 
-                            if self.constant_topology and self.topology is not None:
+                            if self.constant_topology and self.topology is None:
                                 self.topology = frame.topology
 
                         frame_lines = [line]
@@ -278,7 +278,7 @@ def frame_generator(
                     # then increment the frame index
                     frame_index += 1
 
-                if self.constant_topology and self.topology is not None:
+                if self.constant_topology and self.topology is None:
                     self.topology = frame.topology
 
     @runtime_type_checking