Merge pull request #715 from mpharrigan/py3

Python 3 compatitbility

wrappers/python/simtk/openmm/app/dcdfile.py

@@ -70,10 +70,10 @@ class DCDFile(object):
         boxFlag = 0
         if topology.getUnitCellDimensions() is not None:
             boxFlag = 1
-        header = struct.pack('<i4c9if', 84, 'C', 'O', 'R', 'D', 0, firstStep, interval, 0, 0, 0, 0, 0, 0, dt)
+        header = struct.pack('<i4c9if', 84, b'C', b'O', b'R', b'D', 0, firstStep, interval, 0, 0, 0, 0, 0, 0, dt)
         header += struct.pack('<13i', boxFlag, 0, 0, 0, 0, 0, 0, 0, 0, 24, 84, 164, 2)
-        header += struct.pack('<80s', 'Created by OpenMM')
-        header += struct.pack('<80s', 'Created '+time.asctime(time.localtime(time.time())))
+        header += struct.pack('<80s', b'Created by OpenMM')
+        header += struct.pack('<80s', b'Created '+bytes(time.asctime(time.localtime(time.time())), 'ascii'))
         header += struct.pack('<4i', 164, 4, len(list(topology.atoms())), 4)
         file.write(header)
 

wrappers/python/simtk/openmm/app/statedatareporter.py

@@ -99,7 +99,7 @@ class StateDataReporter(object):
                     raise RuntimeError("Cannot write .bz2 file because Python could not import bz2 library")
                 self._out = bz2.BZ2File(file, 'w', 0)
             else:
-                self._out = open(file, 'w', 0)
+                self._out = open(file, 'w')
         else:
             self._out = file
         self._step = step