Question about wxFileDialog usage

I am trying to read in data from a file that I have created. The file
exists, and the following code allows me to select the file for reading.
However when I try to access the data, nothing happens. Here is the code
to run the wxFileDialog and select and open the file.

  #Go ahead and open the data file now so that we don't have
timing problems later.
            #Pop up a dialog to name the data file that we'll take our
input from
            self.datafilesel = wxFileDialog(self, message="Choose a data
file.",
            defaultDir = "C:/",wildcard = "*.dat", )
        
            #Display the File Dialog
            self.datafilesel.ShowModal()
        
            #Kill the File Dialog after obtaining input
            self.datafilesel.Destroy()
            datafile = self.datafilesel.GetFilename()
        
            #Open data file with selected name for reading
            data_file = open('C:/'+datafile, 'r+')

It seems to work to this point, but after a little more code is
executed, I try this:

  if: <snip>
  else: #Transmit data from input file.
                print "Got here.\n"
                for line in data_file.readlines():
                    print "Got here too.\n"
                    print line

I get the first "Got here." but not the "Got here too." Does anyone see
what I am doing wrong here?

--vicki