diff --git a/observation_sim/psf/PSFInterp.py b/observation_sim/psf/PSFInterp.py
index 97435ad048225969fd5287e1dd01a26ef2eb639f..ab902d96859bdbcbe4612871ceac16b82b582abe 100644
--- a/observation_sim/psf/PSFInterp.py
+++ b/observation_sim/psf/PSFInterp.py
@@ -19,7 +19,7 @@ NPSF = 900  # ***# 30*30
 PixSizeInMicrons = 5.  # ***# in microns
 
 
-### find neighbors-KDtree###
+# find neighbors-KDtree #
 def findNeighbors(tx, ty, px, py, dr=0.1, dn=1, OnlyDistance=True):
     """
     find nearest neighbors by 2D-KDTree
@@ -40,9 +40,9 @@ def findNeighbors(tx, ty, px, py, dr=0.1, dn=1, OnlyDistance=True):
 
     dataq = []
     rr = dr
-    if OnlyDistance == True:
+    if OnlyDistance is True:
         dataq = tree.query_ball_point([tx, ty], rr)
-    if OnlyDistance == False:
+    if OnlyDistance is False:
         while len(dataq) < dn:
             dataq = tree.query_ball_point([tx, ty], rr)
             rr += dr
@@ -51,7 +51,7 @@ def findNeighbors(tx, ty, px, py, dr=0.1, dn=1, OnlyDistance=True):
         dataq = np.array(dataq)[ddSortindx[0:dn]]
     return dataq
 
-### find neighbors-hoclist###
+# find neighbors-hoclist#
 
 
 def hocBuild(partx, party, nhocx, nhocy, dhocx, dhocy):
@@ -139,7 +139,7 @@ def findNeighbors_hoclist(px, py, tx=None, ty=None, dn=4, hoc=None, hoclist=None
         return neigh
 
 
-### PSF-IDW###
+# PSF-IDW#
 def psfMaker_IDW(px, py, PSFMat, cen_col, cen_row, IDWindex=2, OnlyNeighbors=True, hoc=None, hoclist=None, PSFCentroidWgt=False):
     """
     psf interpolation by IDW
@@ -163,7 +163,7 @@ def psfMaker_IDW(px, py, PSFMat, cen_col, cen_row, IDWindex=2, OnlyNeighbors=Tru
     npsf = PSFMat[:, :, :].shape[0]
     psfWeight = np.zeros([npsf])
 
-    if OnlyNeighbors == True:
+    if OnlyNeighbors is True:
         if hoc is None:
             neigh = findNeighbors(px, py, cen_col, cen_row,
                                   dr=5., dn=4, OnlyDistance=False)
@@ -175,7 +175,7 @@ def psfMaker_IDW(px, py, PSFMat, cen_col, cen_row, IDWindex=2, OnlyNeighbors=Tru
         neighFlag[neigh] = 1
 
     for ipsf in range(npsf):
-        if OnlyNeighbors == True:
+        if OnlyNeighbors is True:
             if neighFlag[ipsf] != 1:
                 continue
 
@@ -195,7 +195,7 @@ def psfMaker_IDW(px, py, PSFMat, cen_col, cen_row, IDWindex=2, OnlyNeighbors=Tru
 
     psfMaker = np.zeros([ngy, ngx], dtype=np.float32)
     for ipsf in range(npsf):
-        if OnlyNeighbors == True:
+        if OnlyNeighbors is True:
             if neighFlag[ipsf] != 1:
                 continue
 
@@ -208,7 +208,7 @@ def psfMaker_IDW(px, py, PSFMat, cen_col, cen_row, IDWindex=2, OnlyNeighbors=Tru
     return psfMaker
 
 
-### define PSFInterp###
+# define PSFInterp#
 class PSFInterp(PSFModel):
     def __init__(self, chip, npsf=NPSF, PSF_data=None, PSF_data_file=None, PSF_data_prefix="", sigSpin=0, psfRa=0.15, HocBuild=False, LOG_DEBUG=False):
         self.LOG_DEBUG = LOG_DEBUG
@@ -223,7 +223,7 @@ class PSFInterp(PSFModel):
 
         self.iccd = int(chip.getChipLabel(chipID=chip.chipID))
         # self.iccd = chip.chip_name
-        if PSF_data_file == None:
+        if PSF_data_file is None:
             print('Error - PSF_data_file is None')
             sys.exit()
 
@@ -402,7 +402,7 @@ class PSFInterp(PSFModel):
         Spinned PSF: g1, g2 and axis ratio 'a/b'
         """
         a2Rad = np.pi/(60.0*60.0*180.0)
-        
+
         ff = self.sigGauss * 0.107 * (1000.0/10.0) # in unit of [pixels]
         rc = np.sqrt(x*x + y*y)
         cpix = rc*(self.sigSpin*a2Rad)