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Add Python 3 support to Python 2 applications using the six module.

Project description

sixer is a tool adding Python 3 support to a Python 2 project.

sixer was written to produces patches to port OpenStack to Python 3.

It uses basic regular expressions to find code which needs to be modified. It emits warnings when code was not patched or looks suspicious.

Usage <directory or filename> <operation> displays the name of patched files. It displays warnings for code unchanged but which looks suspicious.

If you pass a directory, searchs for .py files in all subdirectories.

Warning: modifies files inplace without asking for confirmation. It’s better to use it in a project managed by a source control manager (ex: git).

Available operations:

  • all
  • basestring
  • iteritems
  • iterkeys
  • itervalues
  • long
  • next
  • raise
  • six_moves
  • stringio
  • unicode
  • urllib
  • xrange


To install sixer, type:

pip install sixer

sixer requires Python 3, it doesn’t work on Python 2.


  • all:
    • combine all operations all together
  • basestring:
    • replace basestring with six.string_types
  • iteritems:
    • replace dict.iteritems() with six.iteritems(dict)
  • itervalues:
    • replace dict.itervalues() with six.itervalues(dict)
  • iterkeys:
    • replace dict.iterkeys() with six.iterkeys(dict)
    • note: for key in dict.iterkeys(): can usually be simplified to for key in dict:
  • long:
    • replace 123L with 123
    • octal number are unchanged (ex: 010L)
  • next:
    • replace with next(iter)
  • raise:
    • replace raise exc[0], exc[1], exc[2] with six.reraise(*exc)
    • replace raise exc_type, exc_value, exc_tb with six.reraise(exc_type, exc_value, exc_tb)
    • replace raise exc, msg with raise exc(msg)
  • six_moves:
    • replace Python 2 imports with imports from six.moves
    • Python 2 modules:
      • BaseHTTPServer
      • ConfigParser
      • Queue
      • __builtin__
      • httplib
      • repr
  • urllib:
    • replace Python 2 urllib and urllib2 with six.moves.urllib
  • stringio:
    • replace StringIO.StringIO with six.StringIO
    • later you may have to replace it with six.StringIO when bytes are expected on Python 3
  • unicode:
    • replace unicode with six.text_type
  • xrange:
    • replace xrange() with range() and add from six.moves import range
    • don’t add the import if all ranges have 1024 items or less

Adding the six import

When an operation uses six, import six may be added. sixer repects OpenStack coding style rules to add the import: imports grouped by standard library, third party and local imports; and imports must be are sorted.

The sixer tool was initially written to produce patches for OpenStack which respects OpenStack coding style, especially the complex rule to group and sort imports.


The project is based on regular expressions, it produces false positives (invalid changes). For example, some operations replace patterns in strings, comments or function names even if it doesn’t make sense.

Try also the 2to6 project which may be more reliable.


To run tests, type tox. Type pip install tox to install the tox program.

Or run tests manually: type python3


  • 2015-05-27: Version 0.3
    • First command line parameter can now be a filename
    • Add “all”, “basestring”, “iterkeys”, “six_moves”, “stringio” and “urllib” operations
    • Enhance the knownledge tables for modules (stdlib, third parties, applications)
    • Ignore unparsable import lines when adding an import
  • 2015-05-12: Version 0.2, first public release

Project details

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