diff --git a/python/swiftest/swiftest/simulation_class.py b/python/swiftest/swiftest/simulation_class.py
index 415af15c1..349e17e64 100644
--- a/python/swiftest/swiftest/simulation_class.py
+++ b/python/swiftest/swiftest/simulation_class.py
@@ -1,10 +1,55 @@
 from swiftest import swiftestio
+
+
 class Simulation:
     """
     This is a class that define the basic Swift/Swifter/Swiftest simulation object
     """
-    def __init__(self, param_file_name, codename="Swiftest"):
-        self.read_param(param_file_name, codename)
+    def __init__(self, codename="Swiftest", source=""):
+        if source == "":
+            self.param = {
+                '! VERSION': f"Swiftest parameter input",
+                'T0': "0.0",
+                'TSTOP': "0.0",
+                'DT': "0.0",
+                'PL_IN': "",
+                'TP_IN': "",
+                'CB_IN': "",
+                'IN_TYPE': "REAL8",
+                'ISTEP_OUT': "1",
+                'ISTEP_DUMP': "1",
+                'BIN_OUT': "bin.dat",
+                'OUT_TYPE': 'REAL8',
+                'OUT_FORM': "XV",
+                'OUT_STAT': "REPLACE",
+                'J2': "0.0",
+                'J4': "0.0",
+                'CHK_RMIN': "-1.0",
+                'CHK_RMAX': "-1.0",
+                'CHK_EJECT': "-1.0",
+                'CHK_QMIN': "-1.0",
+                'CHK_QMIN_COORD': "HELIO",
+                'CHK_QMIN_RANGE': "",
+                'ENC_OUT': "",
+                'MTINY': "-1.0",
+                'MU2KG': "-1.0",
+                'TU2S': "-1.0",
+                'DU2M': "-1.0",
+                'GU': "-1.0",
+                'EXTRA_FORCE': "NO",
+                'BIG_DISCARD': "NO",
+                'CHK_CLOSE': "NO",
+                'FRAGMENTATION': "NO",
+                'MTINY_SET': "NO",
+                'ROTATION': "NO",
+                'TIDES': "NO",
+                'ENERGY': "NO",
+                'GR': "NO",
+                'YARKOVSKY': "NO",
+                'YORP': "NO",
+            }
+        else:
+            self.read_param(source, codename)
         return
     
     def read_param(self, param_file_name, codename="Swiftest"):
diff --git a/python/swiftest/tests/convert_code_type/swifter2swiftest.py b/python/swiftest/tests/convert_code_type/swifter2swiftest.py
index fd41f6c59..4cc62bf8f 100644
--- a/python/swiftest/tests/convert_code_type/swifter2swiftest.py
+++ b/python/swiftest/tests/convert_code_type/swifter2swiftest.py
@@ -10,5 +10,5 @@
 inparam = "param.swifter.in"
 outparam = "param.swifter2swiftest.new"
 print(f"Reading Swift parameter {inparam} and saving it to {outparam}")
-sim = swiftest.Simulation(inparam, codename="Swifter")
+sim = swiftest.Simulation(source=inparam, codename="Swifter")
 oldparam = sim.convert(outparam, newcodename="Swiftest", plname="pl.swifter2swiftest.in", tpname="tp.swifter2swiftest.in", cbname="cb.swifter2swiftest.in")
\ No newline at end of file
diff --git a/python/swiftest/tests/param_readers/param_readers.py b/python/swiftest/tests/param_readers/param_readers.py
index c5b72b57d..d940eecc3 100644
--- a/python/swiftest/tests/param_readers/param_readers.py
+++ b/python/swiftest/tests/param_readers/param_readers.py
@@ -8,17 +8,17 @@
 inparam = "param.swift.in"
 outparam = "param.swift.new"
 print(f"Reading Swift parameter {inparam} and saving it to {outparam}")
-sim = swiftest.Simulation(inparam, codename="Swift")
+sim = swiftest.Simulation(source=inparam, codename="Swift")
 sim.write_param(outparam)
 
 inparam = "param.swifter.in"
 outparam = "param.swifter.new"
 print(f"Reading Swifter parameter {inparam} and saving it to {outparam}")
-sim = swiftest.Simulation(inparam, codename="Swifter")
+sim = swiftest.Simulation(source=inparam, codename="Swifter")
 sim.write_param(outparam)
 
 inparam = "param.swiftest.in"
 outparam = "param.swiftest.new"
 print(f"Reading Swifter parameter {inparam} and saving it to {outparam}")
-sim = swiftest.Simulation(inparam) # The default value of codename is "Swiftest"
+sim = swiftest.Simulation(source=inparam) # The default value of codename is "Swiftest"
 sim.write_param(outparam)
\ No newline at end of file