diff --git a/observation_sim/instruments/FilterParam.py b/observation_sim/instruments/FilterParam.py
index fe109274d48f88d71a8f97cfc1004aa4858f829b..6235eb35f0905f1d16ef66d068affe3d68e2dd89 100755
--- a/observation_sim/instruments/FilterParam.py
+++ b/observation_sim/instruments/FilterParam.py
@@ -25,7 +25,7 @@ class FilterParam(object):
         # 6) sky background: e/pix/s
         # 7) saturation magnitude
         # 8) dim end magnitude
-        if filter_param == None:
+        if filter_param is None:
             filtP = {
                 "NUV":   [2867.7,   705.4,  2470.0,   3270.0,  0.1404, 0.004, 15.7, 25.4],
                 "u":     [3601.1,   852.1,  3120.0,   4090.0,  0.2176, 0.021, 16.1, 25.4],
diff --git a/observation_sim/instruments/FocalPlane.py b/observation_sim/instruments/FocalPlane.py
index 90c2e0e7372cc2d398ab694248364e8fb73da097..8987fcb91cdf1bbf08dd9bd5ede8956049ee61db 100755
--- a/observation_sim/instruments/FocalPlane.py
+++ b/observation_sim/instruments/FocalPlane.py
@@ -9,7 +9,7 @@ class FocalPlane(object):
         self.nchips = 42
         self.ignore_chips = []
 
-        if bad_chips == None:
+        if bad_chips is None:
             self.bad_chips = []
         else:
             self.bad_chips = bad_chips
@@ -80,7 +80,7 @@ class FocalPlane(object):
         if logger is not None:
             logger.info(
                 "    Construct the wcs of the entire image mosaic using Gnomonic/TAN projection")
-        if (xcen == None) or (ycen == None):
+        if (xcen is None) or (ycen is None):
             xcen = self.cen_pix_x
             ycen = self.cen_pix_y
 
diff --git a/observation_sim/instruments/_util.py b/observation_sim/instruments/_util.py
index 953d229d49e04e8818427d8c26fb9e12fbf80780..0947b0a83bab377e781fcebd90807ca47f2c4f87 100755
--- a/observation_sim/instruments/_util.py
+++ b/observation_sim/instruments/_util.py
@@ -46,7 +46,7 @@ def photonEnergy(lambd):
 
 def calculateLimitMag(aperture=2.0, psf_fwhm=0.1969, pixelSize=0.074, pmRation=0.8, throughputFn='i_throughput.txt', readout=5.0, skyFn='sky_emiss_hubble_50_50_A.dat', darknoise=0.02, exTime=150, exNum=1, fw=90000):
     '''
-    description: 
+    description:
     param {*} aperture: unit m, default 2 m
     param {*} psf_fwhm: psf fwhm, default 0.1969"
     param {*} pixelSize: pixel size, default 0.074"
diff --git a/observation_sim/instruments/chip/Chip.py b/observation_sim/instruments/chip/Chip.py
index e50b6640133512bba4da952d5e80613d01d6eda8..ba6bf3b172cc6e4f20e5c866021205705425b14f 100755
--- a/observation_sim/instruments/chip/Chip.py
+++ b/observation_sim/instruments/chip/Chip.py
@@ -191,7 +191,7 @@ class Chip(FocalPlane):
         """Return the filter index and type for a given chip #(chipID)
         """
         filter_type_list = _util.ALL_FILTERS
-        if chipID == None:
+        if chipID is None:
             chipID = self.chipID
 
         # updated configurations
diff --git a/observation_sim/instruments/chip/chip_utils.py b/observation_sim/instruments/chip/chip_utils.py
index cb16118e6916d39a850521f6f164c019cddccf3d..542ed12b3794748ce8372fbda7ea3d5727a6f16d 100644
--- a/observation_sim/instruments/chip/chip_utils.py
+++ b/observation_sim/instruments/chip/chip_utils.py
@@ -206,7 +206,7 @@ def get_poisson(seed=0, sky_level=0.):
 
 
 def get_base_img(img, chip, read_noise, readout_time, dark_noise, exptime=150., InputDark=None):
-    if InputDark == None:
+    if InputDark is None:
         # base_level = read_noise**2 + dark_noise*(exptime+0.5*readout_time)
         # base_level = dark_noise*(exptime+0.5*readout_time)
         base_level = dark_noise*(exptime)
@@ -237,7 +237,7 @@ def add_poisson(img, chip, exptime=150., seed=0, sky_level=0., poisson_noise=Non
     img.addNoise(poisson_noise)
     # img -= read_noise**2
 
-    if InputDark != None:
+    if InputDark is not None:
         # "Instrument/data/dark/dark_1000s_example_0.fits"
         hdu = fits.open(InputDark)
         img += hdu[0].data/hdu[0].header['exptime']*exptime
diff --git a/observation_sim/sim_steps/add_pattern_noise.py b/observation_sim/sim_steps/add_pattern_noise.py
index 959ce8463b2723f392944e23387c8341b9ee4822..dd487ce9e8e05697d1961342c0a7b6b685ca1fc3 100644
--- a/observation_sim/sim_steps/add_pattern_noise.py
+++ b/observation_sim/sim_steps/add_pattern_noise.py
@@ -80,6 +80,6 @@ def add_bias(self, chip, filt, tel, pointing, catalog, obs_param):
                                                nsecy=chip.nsecy,
                                                nsecx=chip.nsecx,
                                                seed=self.overall_config["random_seeds"]["seed_biasNonUniform"]+chip.chipID)
-    elif obs_param["bias_16channel"] == False:
+    elif obs_param["bias_16channel"] is False:
         chip.img += chip.bias_level
     return chip, filt, tel, pointing
diff --git a/run_sim.py b/run_sim.py
index f1179851f87e066259bbc9cbd1e63939da78e3fc..5f14038ea4f3fb2af794f0147067204cc7cd7736 100755
--- a/run_sim.py
+++ b/run_sim.py
@@ -18,7 +18,7 @@ def run_sim():
     Parameters
     ----------
     Catalog : Class
-        a catalog class which is inherited from observation_sim.mock_objects.CatalogBase 
+        a catalog class which is inherited from observation_sim.mock_objects.CatalogBase
 
     Returns
     ----------