Six provides simple utilities for wrapping over differences between Python 2 and Python 3. It is intended to support codebases that work on both Python 2 and 3 without modification. six consists of only one Python file, so it is painless to copy into a project.
Six can be downloaded on PyPI. Its bug tracker and code hosting is on GitHub.
The name, “six”, comes from the fact that 2*3 equals 6. Why not addition? Multiplication is more powerful, and, anyway, “five” has already been snatched away by the (admittedly now moribund) Zope Five project.
-
six.
PY2
A boolean indicating if the code is running on Python 2.
-
six.
PY3
A boolean indicating if the code is running on Python 3.
Constants
Six provides constants that may differ between Python versions. Ones ending
_types
are mostly useful as the second argument to isinstance
or
issubclass
.
-
six.
class_types
Possible class types. In Python 2, this encompasses old-style
py2:types.ClassType
and new-style type
classes. In Python 3,
this is just type
.
-
six.
integer_types
Possible integer types. In Python 2, this is py2:long()
and
py2:int()
, and in Python 3, just py3:int()
.
-
six.
string_types
Possible types for text data. This is py2:basestring()
in Python 2 and
py3:str()
in Python 3.
-
six.
text_type
Type for representing (Unicode) textual data. This is py2:unicode()
in
Python 2 and py3:str()
in Python 3.
-
six.
binary_type
Type for representing binary data. This is py2:str()
in Python 2 and
py3:bytes()
in Python 3.
-
six.
MAXSIZE
The maximum size of a container like py3:list()
or py3:dict()
.
This is equivalent to py3:sys.maxsize
in Python 2.6 and later
(including 3.x). Note, this is temptingly similar to, but not the same as
py2:sys.maxint
in Python 2. There is no direct equivalent to
py2:sys.maxint
in Python 3 because its integer type has no limits
aside from memory.
Here’s example usage of the module:
import six
def dispatch_types(value):
if isinstance(value, six.integer_types):
handle_integer(value)
elif isinstance(value, six.class_types):
handle_class(value)
elif isinstance(value, six.string_types):
handle_string(value)
Object model compatibility
Python 3 renamed the attributes of several interpreter data structures. The
following accessors are available. Note that the recommended way to inspect
functions and methods is the stdlib py3:inspect
module.
-
six.
get_unbound_function
(meth)[source]
Get the function out of unbound method meth. In Python 3, unbound methods don’t exist, so this function just returns meth unchanged. Example usage:
-
six.
get_method_function
(meth)
Get the function out of method object meth.
-
six.
get_method_self
(meth)
Get the self
of bound method meth.
-
six.
get_function_closure
(func)
Get the closure (list of cells) associated with func. This is equivalent
to func.__closure__
on Python 2.6+ and func.func_closure
on Python
2.5.
-
six.
get_function_code
(func)
Get the code object associated with func. This is equivalent to
func.__code__
on Python 2.6+ and func.func_code
on Python 2.5.
-
six.
get_function_defaults
(func)
Get the defaults tuple associated with func. This is equivalent to
func.__defaults__
on Python 2.6+ and func.func_defaults
on Python
2.5.
-
six.
get_function_globals
(func)
Get the globals of func. This is equivalent to func.__globals__
on
Python 2.6+ and func.func_globals
on Python 2.5.
-
six.
next
(it) -
six.
advance_iterator
(it)
Get the next item of iterator it. py3:StopIteration
is raised if
the iterator is exhausted. This is a replacement for calling it.next()
in Python 2 and next(it)
in Python 3. Python 2.6 and above have a
builtin next
function, so six’s version is only necessary for Python 2.5
compatibility.
-
six.
callable
(obj)
Check if obj can be called. Note callable
has returned in Python 3.2,
so using six’s version is only necessary when supporting Python 3.0 or 3.1.
-
six.
iterkeys
(dictionary, **kwargs)[source]
Returns an iterator over dictionary’s keys. This replaces
dictionary.iterkeys()
on Python 2 and dictionary.keys()
on
Python 3. kwargs are passed through to the underlying method.
-
six.
itervalues
(dictionary, **kwargs)[source]
Returns an iterator over dictionary’s values. This replaces
dictionary.itervalues()
on Python 2 and dictionary.values()
on
Python 3. kwargs are passed through to the underlying method.
-
six.
iteritems
(dictionary, **kwargs)[source]
Returns an iterator over dictionary’s items. This replaces
dictionary.iteritems()
on Python 2 and dictionary.items()
on
Python 3. kwargs are passed through to the underlying method.
-
six.
iterlists
(dictionary, **kwargs)[source]
Calls dictionary.iterlists()
on Python 2 and dictionary.lists()
on
Python 3. No builtin Python mapping type has such a method; this method is
intended for use with multi-valued dictionaries like Werkzeug’s.
kwargs are passed through to the underlying method.
-
six.
viewkeys
(dictionary)
Return a view over dictionary’s keys. This replaces
py2:dict.viewkeys()
on Python 2.7 and py3:dict.keys()
on
Python 3.
-
six.
viewvalues
(dictionary)
Return a view over dictionary’s values. This replaces
py2:dict.viewvalues()
on Python 2.7 and py3:dict.values()
on
Python 3.
-
six.
viewitems
(dictionary)
Return a view over dictionary’s items. This replaces
py2:dict.viewitems()
on Python 2.7 and py3:dict.items()
on
Python 3.
-
six.
create_bound_method
(func, obj)
Return a method object wrapping func and bound to obj. On both Python 2
and 3, this will return a py3:types.MethodType()
object. The reason
this wrapper exists is that on Python 2, the MethodType
constructor
requires the obj’s class to be passed.
-
six.
create_unbound_method
(func, cls)[source]
Return an unbound method object wrapping func. In Python 2, this will
return a py2:types.MethodType()
object. In Python 3, unbound methods
do not exist and this wrapper will simply return func.
-
class
six.
Iterator
A class for making portable iterators. The intention is that it be subclassed
and subclasses provide a __next__
method. In Python 2, Iterator
has one method: next
. It simply delegates to __next__
. An alternate
way to do this would be to simply alias next
to __next__
. However,
this interacts badly with subclasses that override
__next__
. Iterator
is empty on Python 3. (In fact, it is just
aliased to py3:object
.)
-
@
six.
wraps
(wrapped, assigned=functools.WRAPPER_ASSIGNMENTS, updated=functools.WRAPPER_UPDATES)[source]
This is exactly the py3:functools.wraps()
decorator, but it sets the
__wrapped__
attribute on what it decorates as py3:functools.wraps()
does on Python versions after 3.2.
Syntax compatibility
These functions smooth over operations which have different syntaxes between Python 2 and 3.
-
six.
exec_
(code, globals=None, locals=None)
Execute code in the scope of globals and locals. code can be a string or a code object. If globals or locals are not given, they will default to the scope of the caller. If just globals is given, it will also be used as locals.
-
six.
print_
(*args, *, file=sys.stdout, end="\n", sep=" ", flush=False)
Print args into file. Each argument will be separated with sep and
end will be written to the file after the last argument is printed. If
flush is true, file.flush()
will be called after all data is written.
-
six.
raise_from
(exc_value, exc_value_from)[source]
Raise an exception from a context. On Python 3, this is equivalent to
raise exc_value from exc_value_from
. On Python 2, which does not support
exception chaining, it is equivalent to raise exc_value
.
-
six.
reraise
(exc_type, exc_value, exc_traceback=None)[source]
Reraise an exception, possibly with a different traceback. In the simple
case, reraise(*sys.exc_info())
with an active exception (in an except
block) reraises the current exception with the last traceback. A different
traceback can be specified with the exc_traceback parameter. Note that
since the exception reraising is done within the reraise()
function,
Python will attach the call frame of reraise()
to whatever traceback is
raised.
-
six.
with_metaclass
(metaclass, *bases)[source]
Create a new class with base classes bases and metaclass metaclass. This is designed to be used in class declarations like this:
Another way to set a metaclass on a class is with the add_metaclass()
decorator.
-
@
six.
add_metaclass
(metaclass)[source]
Class decorator that replaces a normally-constructed class with a metaclass-constructed one. Example usage:
That code produces a class equivalent to
on Python 3 or
on Python 2.
Note that class decorators require Python 2.6. However, the effect of the decorator can be emulated on Python 2.5 like so:
Binary and text data
Python 3 enforces the distinction between byte strings and text strings far more rigorously than Python 2 does; binary data cannot be automatically coerced to or from text data. six provides several functions to assist in classifying string data in all Python versions.
-
six.
b
(data)[source]
A “fake” bytes literal. data should always be a normal string literal. In
Python 2, b()
returns an 8-bit string. In Python 3, data is encoded
with the latin-1 encoding to bytes.
-
six.
u
(text)[source]
A “fake” unicode literal. text should always be a normal string literal.
In Python 2, u()
returns unicode, and in Python 3, a string. Also, in
Python 2, the string is decoded with the unicode-escape
codec, which
allows unicode escapes to be used in it.
-
six.
unichr
(c)
Return the (Unicode) string representing the codepoint c. This is
equivalent to py2:unichr()
on Python 2 and py3:chr()
on Python 3.
-
six.
int2byte
(i)
Converts i to a byte. i must be in range(0, 256)
. This is
equivalent to py2:chr()
in Python 2 and bytes((i,))
in Python 3.
-
six.
byte2int
(bs)
Converts the first byte of bs to an integer. This is equivalent to
ord(bs[0])
on Python 2 and bs[0]
on Python 3.
-
six.
indexbytes
(buf, i)
Return the byte at index i of buf as an integer. This is equivalent to indexing a bytes object in Python 3.
-
six.
iterbytes
(buf)
Return an iterator over bytes in buf as integers. This is equivalent to a bytes object iterator in Python 3.
-
six.
ensure_binary
(s, encoding='utf-8', errors='strict')
Coerce s to binary_type
. encoding, errors are the same as
py3:str.encode()
-
six.
ensure_str
(s, encoding='utf-8', errors='strict')
Coerce s to str
. encoding
, errors
are the same
py3:str.encode()
-
six.
ensure_text
(s, encoding='utf-8', errors='strict')
Coerce s to text_type
. encoding, errors are the same as
py3:str.encode()
-
six.
StringIO
This is a fake file object for textual data. It’s an alias for
py2:StringIO.StringIO
in Python 2 and py3:io.StringIO
in
Python 3.
-
six.
BytesIO
This is a fake file object for binary data. In Python 2, it’s an alias for
py2:StringIO.StringIO
, but in Python 3, it’s an alias for
py3:io.BytesIO
.
-
@
six.
python_2_unicode_compatible
[source]
A class decorator that takes a class defining a __str__
method. On
Python 3, the decorator does nothing. On Python 2, it aliases the
__str__
method to __unicode__
and creates a new __str__
method
that returns the result of __unicode__()
encoded with UTF-8.
unittest assertions
Six contains compatibility shims for unittest assertions that have been renamed. The parameters are the same as their aliases, but you must pass the test method as the first argument. For example:
import six
import unittest
class TestAssertCountEqual(unittest.TestCase):
def test(self):
six.assertCountEqual(self, (1, 2), [2, 1])
Note these functions are only available on Python 2.7 or later.
-
six.
assertCountEqual
()[source]
Alias for assertCountEqual()
on Python 3 and
assertItemsEqual()
on Python 2.
-
six.
assertRaisesRegex
()[source]
Alias for assertRaisesRegex()
on Python 3 and
assertRaisesRegexp()
on Python 2.
-
six.
assertRegex
()[source]
Alias for assertRegex()
on Python 3 and
assertRegexpMatches()
on Python 2.
Renamed modules and attributes compatibility
Python 3 reorganized the standard library and moved several functions to
different modules. Six provides a consistent interface to them through the fake
six.moves
module. For example, to load the module for parsing HTML on
Python 2 or 3, write:
from six.moves import html_parser
Similarly, to get the function to reload modules, which was moved from the
builtin module to the importlib
module, use:
from six.moves import reload_module
For the most part, six.moves
aliases are the names of the modules in
Python 3. When the new Python 3 name is a package, the components of the name
are separated by underscores. For example, html.parser
becomes
html_parser
. In some cases where several modules have been combined, the
Python 2 name is retained. This is so the appropriate modules can be found when
running on Python 2. For example, BaseHTTPServer
which is in
http.server
in Python 3 is aliased as BaseHTTPServer
.
Some modules which had two implementations have been merged in Python 3. For
example, cPickle
no longer exists in Python 3; it was merged with
pickle
. In these cases, fetching the fast version will load the fast one on
Python 2 and the merged module in Python 3.
The py2:urllib
, py2:urllib2
, and py2:urlparse
modules have
been combined in the py3:urllib
package in Python 3. The
six.moves.urllib
package is a version-independent location for this
functionality; its structure mimics the structure of the Python 3
py3:urllib
package.
In order to make imports of the form:
from six.moves.cPickle import loads
work, six places special proxy objects in py3:sys.modules
. These
proxies lazily load the underlying module when an attribute is fetched. This
will fail if the underlying module is not available in the Python
interpreter. For example, sys.modules["six.moves.winreg"].LoadKey
would
fail on any non-Windows platform. Unfortunately, some applications try to
load attributes on every module in py3:sys.modules
. six mitigates
this problem for some applications by pretending attributes on unimportable
modules do not exist. This hack does not work in every case, though. If you are
encountering problems with the lazy modules and don’t use any from imports
directly from six.moves
modules, you can workaround the issue by removing
the six proxy modules:
d = [name for name in sys.modules if name.startswith("six.moves.")]
for name in d:
del sys.modules[name]
Supported renames:
Name | Python 2 name | Python 3 name |
---|---|---|
builtins |
py2:__builtin__ |
py3:builtins |
configparser |
py2:ConfigParser |
py3:configparser |
copyreg |
py2:copy_reg |
py3:copyreg |
cPickle |
py2:cPickle |
py3:pickle |
cStringIO |
py2:cStringIO.StringIO() |
py3:io.StringIO |
dbm_gnu |
py2:gdbm() |
py3:dbm.gnu |
_dummy_thread |
py2:dummy_thread |
py3:_dummy_thread |
email_mime_base |
py2:email.MIMEBase |
py3:email.mime.base |
email_mime_image |
py2:email.MIMEImage |
py3:email.mime.image |
email_mime_multipart |
py2:email.MIMEMultipart |
py3:email.mime.multipart |
email_mime_nonmultipart |
py2:email.MIMENonMultipart |
py3:email.mime.nonmultipart |
email_mime_text |
py2:email.MIMEText |
py3:email.mime.text |
filter |
py2:itertools.ifilter() |
py3:filter() |
filterfalse |
py2:itertools.ifilterfalse() |
py3:itertools.filterfalse() |
getcwd |
py2:os.getcwdu() |
py3:os.getcwd() |
getcwdb |
py2:os.getcwd() |
py3:os.getcwdb() |
getoutput |
py2:commands.getoutput() |
py3:subprocess.getoutput() |
http_cookiejar |
py2:cookielib |
py3:http.cookiejar |
http_cookies |
py2:Cookie |
py3:http.cookies |
html_entities |
py2:htmlentitydefs |
py3:html.entities |
html_parser |
py2:HTMLParser |
py3:html.parser |
http_client |
py2:httplib |
py3:http.client |
BaseHTTPServer |
py2:BaseHTTPServer |
py3:http.server |
CGIHTTPServer |
py2:CGIHTTPServer |
py3:http.server |
SimpleHTTPServer |
py2:SimpleHTTPServer |
py3:http.server |
input |
py2:raw_input() |
py3:input() |
intern |
py2:intern() |
py3:sys.intern() |
map |
py2:itertools.imap() |
py3:map() |
queue |
py2:Queue |
py3:queue |
range |
py2:xrange() |
py3:range() |
reduce |
py2:reduce() |
py3:functools.reduce() |
reload_module |
py2:reload() |
py3:imp.reload() ,
py3:importlib.reload()
on Python 3.4+ |
reprlib |
py2:repr |
py3:reprlib |
shlex_quote |
py2:pipes.quote |
py3:shlex.quote |
socketserver |
py2:SocketServer |
py3:socketserver |
_thread |
py2:thread |
py3:_thread |
tkinter |
py2:Tkinter |
py3:tkinter |
tkinter_dialog |
py2:Dialog |
py3:tkinter.dialog |
tkinter_filedialog |
py2:FileDialog |
py3:tkinter.FileDialog |
tkinter_scrolledtext |
py2:ScrolledText |
py3:tkinter.scrolledtext |
tkinter_simpledialog |
py2:SimpleDialog |
py3:tkinter.simpledialog |
tkinter_ttk |
py2:ttk |
py3:tkinter.ttk |
tkinter_tix |
py2:Tix |
py3:tkinter.tix |
tkinter_constants |
py2:Tkconstants |
py3:tkinter.constants |
tkinter_dnd |
py2:Tkdnd |
py3:tkinter.dnd |
tkinter_colorchooser |
py2:tkColorChooser |
py3:tkinter.colorchooser |
tkinter_commondialog |
py2:tkCommonDialog |
py3:tkinter.commondialog |
tkinter_tkfiledialog |
py2:tkFileDialog |
py3:tkinter.filedialog |
tkinter_font |
py2:tkFont |
py3:tkinter.font |
tkinter_messagebox |
py2:tkMessageBox |
py3:tkinter.messagebox |
tkinter_tksimpledialog |
py2:tkSimpleDialog |
py3:tkinter.simpledialog |
urllib.parse |
See six.moves.urllib.parse |
py3:urllib.parse |
urllib.error |
See six.moves.urllib.error |
py3:urllib.error |
urllib.request |
See six.moves.urllib.request |
py3:urllib.request |
urllib.response |
See six.moves.urllib.response |
py3:urllib.response |
urllib.robotparser |
py2:robotparser |
py3:urllib.robotparser |
urllib_robotparser |
py2:robotparser |
py3:urllib.robotparser |
UserDict |
py2:UserDict.UserDict |
py3:collections.UserDict |
UserList |
py2:UserList.UserList |
py3:collections.UserList |
UserString |
py2:UserString.UserString |
py3:collections.UserString |
winreg |
py2:_winreg |
py3:winreg |
xmlrpc_client |
py2:xmlrpclib |
py3:xmlrpc.client |
xmlrpc_server |
py2:SimpleXMLRPCServer |
py3:xmlrpc.server |
xrange |
py2:xrange() |
py3:range() |
zip |
py2:itertools.izip() |
py3:zip() |
zip_longest |
py2:itertools.izip_longest() |
py3:itertools.zip_longest() |
urllib parse
Contains functions from Python 3’s py3:urllib.parse
and Python 2’s:
py2:urlparse
:
py2:urlparse.ParseResult()
py2:urlparse.SplitResult()
py2:urlparse.urlparse()
py2:urlparse.urlunparse()
py2:urlparse.parse_qs()
py2:urlparse.parse_qsl()
py2:urlparse.urljoin()
py2:urlparse.urldefrag()
py2:urlparse.urlsplit()
py2:urlparse.urlunsplit()
py2:urlparse.splitquery()
py2:urlparse.uses_fragment()
py2:urlparse.uses_netloc()
py2:urlparse.uses_params()
py2:urlparse.uses_query()
py2:urlparse.uses_relative()
and py2:urllib
:
py2:urllib.quote()
py2:urllib.quote_plus()
py2:urllib.splittag()
py2:urllib.splituser()
py2:urllib.splitvalue()
py2:urllib.unquote()
(also exposed aspy3:urllib.parse.unquote_to_bytes()
)py2:urllib.unquote_plus()
py2:urllib.urlencode()
urllib error
Contains exceptions from Python 3’s py3:urllib.error
and Python 2’s:
py2:urllib
:
py2:urllib.ContentTooShortError
and py2:urllib2
:
py2:urllib2.URLError
py2:urllib2.HTTPError
urllib request
Contains items from Python 3’s py3:urllib.request
and Python 2’s:
py2:urllib
:
py2:urllib.pathname2url()
py2:urllib.url2pathname()
py2:urllib.getproxies()
py2:urllib.urlretrieve()
py2:urllib.urlcleanup()
py2:urllib.URLopener
py2:urllib.FancyURLopener
py2:urllib.proxy_bypass()
and py2:urllib2
:
py2:urllib2.urlopen()
py2:urllib2.install_opener()
py2:urllib2.build_opener()
py2:urllib2.parse_http_list()
py2:urllib2.parse_keqv_list()
py2:urllib2.Request
py2:urllib2.OpenerDirector
py2:urllib2.HTTPDefaultErrorHandler
py2:urllib2.HTTPRedirectHandler
py2:urllib2.HTTPCookieProcessor
py2:urllib2.ProxyHandler
py2:urllib2.BaseHandler
py2:urllib2.HTTPPasswordMgr
py2:urllib2.HTTPPasswordMgrWithDefaultRealm
py2:urllib2.AbstractBasicAuthHandler
py2:urllib2.HTTPBasicAuthHandler
py2:urllib2.ProxyBasicAuthHandler
py2:urllib2.AbstractDigestAuthHandler
py2:urllib2.HTTPDigestAuthHandler
py2:urllib2.ProxyDigestAuthHandler
py2:urllib2.HTTPHandler
py2:urllib2.HTTPSHandler
py2:urllib2.FileHandler
py2:urllib2.FTPHandler
py2:urllib2.CacheFTPHandler
py2:urllib2.UnknownHandler
py2:urllib2.HTTPErrorProcessor
urllib response
Contains classes from Python 3’s py3:urllib.response
and Python 2’s:
py2:urllib
:
py2:urllib.addbase
py2:urllib.addclosehook
py2:urllib.addinfo
py2:urllib.addinfourl
Advanced - Customizing renames
It is possible to add additional names to the six.moves
namespace.
-
six.
add_move
(item)[source]
Add item to the six.moves
mapping. item should be a
MovedAttribute
or MovedModule
instance.
Instances of the following classes can be passed to add_move()
. Neither
have any public members.
-
class
six.
MovedModule
(name, old_mod, new_mod)[source]
Create a mapping for six.moves
called name that references different
modules in Python 2 and 3. old_mod is the name of the Python 2 module.
new_mod is the name of the Python 3 module.
-
class
six.
MovedAttribute
(name, old_mod, new_mod, old_attr=None, new_attr=None)[source]
Create a mapping for six.moves
called name that references different
attributes in Python 2 and 3. old_mod is the name of the Python 2 module.
new_mod is the name of the Python 3 module. If new_attr is not given, it
defaults to old_attr. If neither is given, they both default to name.