old_contents: import os
  
  # USAGE NOTES:
  #
  # Please update compiler paths according to your environment.
  #
  # It is not required to configure all supported compilers - any subset will work (even empty).
  # It is okay to have entries with invalid paths for some compilers, they will be skipped.
  
  compilers = {}
  
  if os.name == 'nt':
      # Windows configuration example
      compilers = {
          'msvc'  : r'C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat',
          'dmd'   : r'C:\D\dmd2\windows\bin\rdmd.exe',
          'gdc'   : r'C:\D\gdc\bin\gdc.exe',
          'ldc'   : r'C:\D\ldc\bin\ldc2.exe',
          'go'    : r'C:\Go\bin\go.exe',
      }
  else:
      # Linux/OS X configuration example
      compilers = {
          'gcc'   : r'/usr/bin/g++',
          'clang' : r'/usr/bin/clang++-3.6',
          'dmd'   : r'/usr/bin/rdmd',
          'gdc'   : r'/usr/local/gdc/bin/gdc',
          'ldc'   : r'/usr/local/ldc/bin/ldc2',
          'go'    : r'/usr/local/go/bin/go',
          'gccgo' : r'/usr/bin/gccgo',
      }
  
new_contents: import os
  from collections import OrderedDict
  
  # USAGE NOTES:
  #
  # Please update compiler paths according to your environment.
  #
  # It is not required to configure all supported compilers - any subset will work (even empty).
  # It is okay to have entries with invalid paths for some compilers, they will be skipped.
  
  compilers = None
  
  if os.name == 'nt':
      # Windows configuration example
      compilers = OrderedDict([
          ('msvc', r'C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat'),
          ('dmd' , r'C:\D\dmd2\windows\bin\rdmd.exe'),
          ('gdc' , r'C:\D\gdc\bin\gdc.exe'),
          ('ldc' , r'C:\D\ldc2\bin\ldc2.exe'),
          ('go'  , r'C:\Go\bin\go.exe'),
      ])
  else:
      # Linux/OS X configuration example
      compilers = OrderedDict([
          ('gcc'  , r'/usr/bin/g++'),
          ('clang', r'/usr/bin/clang++-3.6'),
          ('dmd'  , r'/usr/bin/rdmd'),
          ('gdc'  , r'/usr/local/gdc/bin/gdc'),
          ('ldc'  , r'/usr/local/ldc/bin/ldc2'),
          ('go'   , r'/usr/local/go/bin/go'),
          ('gccgo', r'/usr/bin/gccgo'),
      ])
  
subject: Use ordered dictionary to store compilers configuration. Ordered dictionary allows to print the list of compilers always in the same order (also matches the order specified by configuration file).