code: def writeXYCatalog(self,filename):
          
          if self.xypos is None:
              warnstr = textutil.textbox(
                  'WARNING: \n    No X,Y source catalog to write to file. ')
              for line in warnstr.split('\n'):
                  log.warning(line)
              print(warnstr)
              return
  
          f = open(filename,'w')
          f.write("# Source catalog derived for %s\n"%self.wcs.filename)
          f.write("# Columns: \n")
          if self.use_sharp_round:
              f.write('#    X      Y         Flux       ID      Sharp       Round1       Round2\n')
          else:
              f.write('#    X      Y         Flux       ID\n')
          f.write('#   (%s)   (%s)\n'%(self.in_units,self.in_units))
  
          for row in range(len(self.xypos[0])):
              for i in range(len(self.xypos)):
                  f.write("%g  "%(self.xypos[i][row]))
              f.write("\n")
  
          f.close()
docs: Write out the X,Y catalog to a file