diff --git a/ess/TraceWin.py b/ess/TraceWin.py
index b3d6e04310afc074b7350ff93a49d93f3f303062..29d326524955bfa9886aa53868beb6217766f581 100644
--- a/ess/TraceWin.py
+++ b/ess/TraceWin.py
@@ -55,7 +55,7 @@ class dst:
 
         import numpy
 
-        fin=file(self.filename,'r')
+        fin=open(self.filename,'r')
 
         # dummy, Np, Ib, freq, dummy
         Header_type = numpy.dtype([
@@ -262,7 +262,7 @@ class plt:
 
         import numpy
 
-        fin=file(self.filename,'r')
+        fin=open(self.filename,'r')
 
         # dummy, Np, Ib, freq, dummy
         Header_type = numpy.dtype([
@@ -502,7 +502,7 @@ class density_file:
 
 
         self.filename=filename
-        self.fin=file(self.filename, 'r')
+        self.fin=open(self.filename, 'r')
 
         if envelope==None: # try to guess
             if filename.split('/')[-1].split('.')[0]=='Density_Env':
@@ -963,7 +963,7 @@ class remote_data_merger:
 
         if self._files:
             for f in self._files:
-                string=file(f,'r').read()
+                string=open(f,'r').read()
                 split=string.split('$$$')
                 if split[9]!='Data_Error':
                     raise ValueError("Magic problem, please complain to Yngve")
@@ -1000,7 +1000,7 @@ class remote_data_merger:
             data=h1+d1+h2+d2+d3
 
             if filename:
-                file(filename,'w').write('\n'.join(data))
+                open(filename,'w').write('\n'.join(data))
 
             return data
 
@@ -1047,7 +1047,7 @@ class field_map:
 
         if not os.path.isfile(filename):
             raise ValueError("Cannot find file {}".format(filename))
-        fin = file(filename,'r')
+        fin = open(filename,'r')
         l=fin.readline().split()
         self.start=[]
         self.end=[]
@@ -1072,7 +1072,7 @@ class field_map:
         self.map=numpy.loadtxt(fin).reshape(numindexes)
 
     def savemap(self, filename):
-        fout=file(filename,'w')
+        fout=open(filename,'w')
         for n,s in zip(self.map.shape,self.size):
             fout.write('{} {}\n'.format(n-1,s))
         fout.write('{}\n'.format(self.norm))