diff --git a/src/chilife/RotamerEnsemble.py b/src/chilife/RotamerEnsemble.py
index 6d681f8..5e383cc 100644
--- a/src/chilife/RotamerEnsemble.py
+++ b/src/chilife/RotamerEnsemble.py
@@ -1362,6 +1362,12 @@ def set_dihedral_sampling_sigmas(self, value):
             raise ValueError('`dihedral_sigmas` must be a scalar, an array the length of the `self.dihedral atoms` or '
                              'an array with the shape of (len(self.weights), len(self.dihedral_atoms))')
 
+    @property
+    def partition_function(self):
+        """The partition function of the rotamer ensemble after reweighting."""
+        if self.partition == 1 and self.protein is not None:
+            self.evaluate ()
+        return self.partition
 
 def assign_defaults(kwargs):
     """
diff --git a/src/chilife/dRotamerEnsemble.py b/src/chilife/dRotamerEnsemble.py
index 2ffe8e5..9a2b419 100644
--- a/src/chilife/dRotamerEnsemble.py
+++ b/src/chilife/dRotamerEnsemble.py
@@ -718,6 +718,13 @@ def copy(self):
             else:
                 new_copy.__dict__[item] = deepcopy(self.__dict__[item])
         return new_copy
+    
+    @property
+    def partition_function(self):
+        """The partition function of the rotamer ensemble after reweighting."""
+        if self.partition == 1 and self.protein is not None:
+            self.evaluate()
+        return self.partition
 
 def proc_sites(sites):
     sites = sorted(sites)
@@ -792,4 +799,4 @@ def dassign_defaults(kwargs):
             f'{", ".join(key for key in kwargs if key not in defaults)}'
         )
 
-    return kwargs_filled.items()
\ No newline at end of file
+    return kwargs_filled.items()