diff --git a/src/quemb/kbe/autofrag.py b/src/quemb/kbe/autofrag.py
index 55f2bc9f..217cc0b0 100644
--- a/src/quemb/kbe/autofrag.py
+++ b/src/quemb/kbe/autofrag.py
@@ -1,6 +1,5 @@
 # Author(s): Oinam Romesh Meitei
 
-import sys
 
 import numpy
 from numpy.linalg import norm
diff --git a/src/quemb/kbe/lo.py b/src/quemb/kbe/lo.py
index a571cae7..f502b3ce 100644
--- a/src/quemb/kbe/lo.py
+++ b/src/quemb/kbe/lo.py
@@ -2,7 +2,6 @@
 #            Henry Tran
 #
 import os
-import sys
 
 import numpy
 from libdmet.lo import pywannier90
diff --git a/src/quemb/kbe/pbe.py b/src/quemb/kbe/pbe.py
index feaf115a..b220ae56 100644
--- a/src/quemb/kbe/pbe.py
+++ b/src/quemb/kbe/pbe.py
@@ -2,7 +2,6 @@
 
 import os
 import pickle
-import sys
 from multiprocessing import Pool
 
 import h5py
diff --git a/src/quemb/kbe/pfrag.py b/src/quemb/kbe/pfrag.py
index 3a9cb6c1..5f47ed9e 100644
--- a/src/quemb/kbe/pfrag.py
+++ b/src/quemb/kbe/pfrag.py
@@ -1,6 +1,5 @@
 # Author(s): Oinam Romesh Meitei
 
-import sys
 
 import h5py
 import numpy
diff --git a/src/quemb/molbe/_opt.py b/src/quemb/molbe/_opt.py
index 6da4d697..f15ff6f1 100644
--- a/src/quemb/molbe/_opt.py
+++ b/src/quemb/molbe/_opt.py
@@ -1,6 +1,5 @@
 # Author(s): Oinam Romesh Meitei
 
-import sys
 
 import numpy
 
diff --git a/src/quemb/molbe/autofrag.py b/src/quemb/molbe/autofrag.py
index 3c3ec125..2b6fe95a 100644
--- a/src/quemb/molbe/autofrag.py
+++ b/src/quemb/molbe/autofrag.py
@@ -1,6 +1,5 @@
 # Author: Oinam Romesh Meitei
 
-import sys
 
 from numpy.linalg import norm
 
diff --git a/src/quemb/molbe/be_parallel.py b/src/quemb/molbe/be_parallel.py
index d04226f8..61f8898b 100644
--- a/src/quemb/molbe/be_parallel.py
+++ b/src/quemb/molbe/be_parallel.py
@@ -1,7 +1,6 @@
 # Author(s): Oinam Romesh Meitei, Leah Weisburn
 
 import os
-import sys
 from multiprocessing import Pool
 
 import numpy
diff --git a/src/quemb/molbe/fragment.py b/src/quemb/molbe/fragment.py
index 4cbad384..f6b6589f 100644
--- a/src/quemb/molbe/fragment.py
+++ b/src/quemb/molbe/fragment.py
@@ -1,6 +1,5 @@
 # Author: Oinam Romesh Meitei
 
-import sys
 
 from quemb.molbe.autofrag import autogen
 from quemb.molbe.helper import get_core
diff --git a/src/quemb/molbe/lchain.py b/src/quemb/molbe/lchain.py
index f72040b7..34aeacf2 100644
--- a/src/quemb/molbe/lchain.py
+++ b/src/quemb/molbe/lchain.py
@@ -1,7 +1,5 @@
 # Author(s): Oinam Romesh Meitei
 
-import sys
-
 
 def chain(self, mol, frozen_core=False, closed=False):
     """
diff --git a/src/quemb/molbe/lo.py b/src/quemb/molbe/lo.py
index 5265547d..3f7401ac 100644
--- a/src/quemb/molbe/lo.py
+++ b/src/quemb/molbe/lo.py
@@ -1,6 +1,5 @@
 # Author(s): Henry Tran, Oinam Meitei, Shaun Weatherly
 #
-import sys
 
 import numpy
 from numpy.linalg import eigh, inv, multi_dot, norm, svd
diff --git a/src/quemb/molbe/mbe.py b/src/quemb/molbe/mbe.py
index 2548290c..b09a7e61 100644
--- a/src/quemb/molbe/mbe.py
+++ b/src/quemb/molbe/mbe.py
@@ -2,7 +2,6 @@
 
 import os
 import pickle
-import sys
 
 import h5py
 import numpy
diff --git a/src/quemb/molbe/misc.py b/src/quemb/molbe/misc.py
index 62f3980a..606045b6 100644
--- a/src/quemb/molbe/misc.py
+++ b/src/quemb/molbe/misc.py
@@ -1,7 +1,6 @@
 # Author(s): Minsik Cho, Leah Weisburn
 
 import os
-import sys
 import time
 
 import h5py
diff --git a/src/quemb/molbe/solver.py b/src/quemb/molbe/solver.py
index 84563d0f..46ffca75 100644
--- a/src/quemb/molbe/solver.py
+++ b/src/quemb/molbe/solver.py
@@ -1,8 +1,6 @@
 # Author(s): Oinam Romesh Meitei, Leah Weisburn, Shaun Weatherly
 
 import os
-import sys
-from typing import Optional
 
 import numpy
 from numpy.linalg import multi_dot
diff --git a/src/quemb/shared/helper.py b/src/quemb/shared/helper.py
index 7b6fe658..8973e2ea 100644
--- a/src/quemb/shared/helper.py
+++ b/src/quemb/shared/helper.py
@@ -1,4 +1,3 @@
-import sys
 from pathlib import Path
 from typing import Any, Callable, Optional, TypeVar