diff --git a/observation_sim/instruments/chip/libCTI/CTI_modeling.py b/observation_sim/instruments/chip/libCTI/CTI_modeling.py
index 6c840599d15fc24a779f554b4abd05527017bc84..fdf8b41a99c544f291f6970083ffaca0c9b49849 100644
--- a/observation_sim/instruments/chip/libCTI/CTI_modeling.py
+++ b/observation_sim/instruments/chip/libCTI/CTI_modeling.py
@@ -31,7 +31,7 @@ def get_trap_map(seeds,nx,ny,nmax,rho_trap,beta,c,out_dir):
     get_trap_h(seeds_p,c_int(int(nsp)),c_int(int(nx)),c_int(int(ny)),\
             c_int(int(nmax)),rho_trap_p,c_float(beta),\
             c_float(c),filename)
-        
+
 def bin2fits(bin_file,fits_dir,nsp,nx,ny,nmax):
     data = np.fromfile(bin_file,dtype=np.float32)
     data = data.reshape(nx,nsp,ny,nmax).transpose(1,3,2,0)
@@ -101,6 +101,6 @@ if __name__ =='__main__':
     image = fits.getdata("inputdata/image.fits").astype(np.int32)
     get_trap_map(trap_seeds,nx,ny,nmax,rho_trap,beta,c,".")
     bin2fits("trap.bin",".",nsp,nx,ny,nmax)
-    image_cti = CTI_sim(image,nx,ny,noverscan,nsp,nmax,beta,w,c,t,rho_trap,trap_seeds,release_seed)  
+    image_cti = CTI_sim(image,nx,ny,noverscan,nsp,nmax,beta,w,c,t,rho_trap,trap_seeds,release_seed)
     fits.writeto("output/image_CTI.fits",data=image_cti,overwrite=True)
 """
diff --git a/observation_sim/psf/PSFGauss.py b/observation_sim/psf/PSFGauss.py
index e3036d9293c37397505a4abf65b367b5d9429a8f..0d3e8b0842e93594228d4619f77f3e91a1dd5976 100644
--- a/observation_sim/psf/PSFGauss.py
+++ b/observation_sim/psf/PSFGauss.py
@@ -50,7 +50,7 @@ class PSFGauss(PSFModel):
 
         Return: the flux ratio
         """
-        if pscale == None:
+        if pscale is None:
             pscale = self.pix_size
         gaussx = galsim.Gaussian(flux=1.0, sigma=sig)
         gaussImg = gaussx.drawImage(scale=pscale, method='no_pixel')
@@ -68,7 +68,7 @@ class PSFGauss(PSFModel):
 
         return the fwhm in arcsec
         """
-        if pscale == None:
+        if pscale is None:
             pscale = self.pix_size
         err = 1.0e-3
         nxx = 100
@@ -122,4 +122,5 @@ class PSFGauss(PSFModel):
 
         # return ell, beta, qr
         PSFshear = galsim.Shear(e=ell, beta=beta*galsim.radians)
-        return self.psf.shear(PSFshear), PSFshear
\ No newline at end of file
+        return self.psf.shear(PSFshear), PSFshear
+