diff --git a/catalog/Catalog_example.py b/catalog/Catalog_example.py
index 4b51f0a2dd1213294ffcc21f50fe780250c32067..d3a6f28c1e050bf95fb4c4c1e9d8cf36671c5179 100644
--- a/catalog/Catalog_example.py
+++ b/catalog/Catalog_example.py
@@ -72,7 +72,7 @@ class Catalog(CatalogBase):
         This is a must implemented method which is used to read in all objects, and
         then convert them to observation_sim.mock_objects (Star, Galaxy, or Quasar).
 
-        Currently, 
+        Currently,
         the model of observation_sim.mock_objects.Star class requires:
             param["star"] : int
                 specify the object type: 0: galaxy, 1: star, 2: quasar
@@ -84,7 +84,7 @@ class Catalog(CatalogBase):
                 Declination (in degrees)
             param["mag_use_normal"]: float
                 the absolute magnitude in a particular filter
-                NOTE: if that filter is not the corresponding CSST filter, the 
+                NOTE: if that filter is not the corresponding CSST filter, the
                 load_norm_filt(obj) function must be implemented to load the filter
                 throughput of that particular photometric system
 
@@ -99,7 +99,7 @@ class Catalog(CatalogBase):
                 Declination (in degrees)
             param["mag_use_normal"]: float
                 the absolute magnitude in a particular filter
-                NOTE: if that filter is not the corresponding CSST filter, the 
+                NOTE: if that filter is not the corresponding CSST filter, the
                 load_norm_filt(obj) function must be implemented to load the filter
                 throughput of that particular photometric system
             param["bfrac"] : float
diff --git a/catalog/testCat_fits.py b/catalog/testCat_fits.py
index 6ae1bada7eb8b6ff34db22ec4aaa6f725de69219..9717b22ab0315d594491a9ca54ac39eaf2686dbf 100644
--- a/catalog/testCat_fits.py
+++ b/catalog/testCat_fits.py
@@ -177,7 +177,7 @@ class Catalog(CatalogBase):
             # param["CSSTmag"]= True
             # param["mag_r"] = 20.
             # param['']
-            ### more keywords for stamp###
+            # more keywords for stamp#
             param['image'] = hdu[0].data
             param['image'] = param['image']/(np.sum(param['image']))
             obj = Stamp(param)
diff --git a/observation_sim/ObservationSim.py b/observation_sim/ObservationSim.py
index cb060ab4d65520e8a3ae76b5b5f678a88cfe43d0..523406e56d2161459015febfa7abe3b4e1e70d26 100755
--- a/observation_sim/ObservationSim.py
+++ b/observation_sim/ObservationSim.py
@@ -25,7 +25,7 @@ class Observation(object):
 
     def prepare_chip_for_exposure(self, chip, ra_cen, dec_cen, pointing, wcs_fp=None, slsPSFOptim=False):
         # Get WCS for the focal plane
-        if wcs_fp == None:
+        if wcs_fp is None:
             wcs_fp = self.focal_plane.getTanWCS(
                 ra_cen, dec_cen, pointing.img_pa, chip.pix_scale)
 
diff --git a/observation_sim/config/__init__.py b/observation_sim/config/__init__.py
index bf03e61f5078114b03a38a19d2b43fae72b13341..6d22c04fcbae1968fd952e7ac4b8110a23d05667 100644
--- a/observation_sim/config/__init__.py
+++ b/observation_sim/config/__init__.py
@@ -1,2 +1,2 @@
 from .ChipOutput import ChipOutput
-from .Pointing import Pointing
\ No newline at end of file
+from .Pointing import Pointing
diff --git a/observation_sim/config/header/__init__.py b/observation_sim/config/header/__init__.py
index db07f26a1fca8b82fd63fa1fc526b5547d47b120..bbe9ba53b9461420ef1a32bbc53e54ccc77cc4c0 100755
--- a/observation_sim/config/header/__init__.py
+++ b/observation_sim/config/header/__init__.py
@@ -1,2 +1,2 @@
 from .ImageHeader import generatePrimaryHeader
-from .ImageHeader import generateExtensionHeader
\ No newline at end of file
+from .ImageHeader import generateExtensionHeader