six
Benjamin Peterson <benjamin@python.org>
Benjamin Peterson <benjamin@python.org>
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.
genindex
search
PY2
A boolean indicating if the code is running on Python 2.
PY3
A boolean indicating if the code is running on Python 3.
Six provides constants that may differ between Python versions. Ones ending _types
are mostly useful as the second argument to isinstance
or issubclass
.
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
.
integer_types
Possible integer types. In Python 2, this is py2:long
and py2:int
, and in Python 3, just py3:int
.
string_types
Possible types for text data. This is py2:basestring
in Python 2 and py3:str
in Python 3.
text_type
Type for representing (Unicode) textual data. This is py2:unicode
in Python 2 and py3:str
in Python 3.
binary_type
Type for representing binary data. This is py2:str
in Python 2 and py3:bytes
in Python 3. Python 2.6 and 2.7 include bytes
as a builtin alias of str
, so six’s version is only necessary for Python 2.5 compatibility.
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)
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.
get_unbound_function(meth)
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:
from six import get_unbound_function
class X(object):
def method(self):
pass
method_function = get_unbound_function(X.method)
get_method_function(meth)
Get the function out of method object meth.
get_method_self(meth)
Get the self
of bound method meth.
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.
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.
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.
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.
next(it) 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.
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.
iterkeys(dictionary, **kwargs)
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.
itervalues(dictionary, **kwargs)
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.
iteritems(dictionary, **kwargs)
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.
iterlists(dictionary, **kwargs)
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.
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.
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.
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.
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.
create_unbound_method(func, cls)
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.
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
.)
wraps(wrapped, assigned=functools.WRAPPER_ASSIGNMENTS, updated=functools.WRAPPER_UPDATES)
This is Python 3.2's py3:functools.wraps
decorator. It sets the __wrapped__
attribute on what it decorates. It doesn't raise an error if any of the attributes mentioned in assigned
and updated
are missing on wrapped
object.
These functions smooth over operations which have different syntaxes between Python 2 and 3.
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.
Note
Python 3's py3:exec
doesn't take keyword arguments, so calling exec
with them should be avoided.
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.
Note
In Python 2, this function imitates Python 3's py3:print
by not having softspace support. If you don't know what that is, you're probably ok. :)
raise_from(exc_value, exc_value_from)
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
.
reraise(exc_type, exc_value, exc_traceback=None)
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.
with_metaclass(metaclass, *bases)
Create a new class with base classes bases and metaclass metaclass. This is designed to be used in class declarations like this: :
from six import with_metaclass
class Meta(type):
pass
class Base(object):
pass
class MyClass(with_metaclass(Meta, Base)):
pass
Another way to set a metaclass on a class is with the add_metaclass
decorator.
add_metaclass(metaclass)
Class decorator that replaces a normally-constructed class with a metaclass-constructed one. Example usage: :
@add_metaclass(Meta)
class MyClass(object):
pass
That code produces a class equivalent to :
class MyClass(object, metaclass=Meta):
pass
on Python 3 or :
class MyClass(object):
__metaclass__ = Meta
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:
class MyClass(object):
pass
MyClass = add_metaclass(Meta)(MyClass)
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.
b(data)
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.
Note
Since all Python versions 2.6 and after support the b
prefix, code without 2.5 support doesn't need b
.
u(text)
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.
Note
In Python 3.3, the u
prefix has been reintroduced. Code that only supports Python 3 versions of 3.3 and higher thus does not need u
.
Note
On Python 2, u
doesn't know what the encoding of the literal is. Each byte is converted directly to the unicode codepoint of the same value. Because of this, it's only safe to use u
with strings of ASCII data.
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.
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.
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.
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.
iterbytes(buf)
Return an iterator over bytes in buf as integers. This is equivalent to a bytes object iterator in Python 3.
ensure_binary(s, encoding='utf-8', errors='strict')
Coerce s to binary_type
. encoding, errors are the same as py3:str.encode
ensure_str(s, encoding='utf-8', errors='strict')
Coerce s to str
. encoding, errors are the same as py3:str.encode
ensure_text(s, encoding='utf-8', errors='strict')
Coerce s to text_type
. encoding, errors are the same as py3:str.encode
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.
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
.
python_2_unicode_compatible
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.
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.
assertCountEqual()
Alias for ~py3:unittest.TestCase.assertCountEqual
on Python 3 and ~py2:unittest.TestCase.assertItemsEqual
on Python 2.
assertRaisesRegex()
Alias for ~py3:unittest.TestCase.assertRaisesRegex
on Python 3 and ~py2:unittest.TestCase.assertRaisesRegexp
on Python 2.
assertRegex()
Alias for ~py3:unittest.TestCase.assertRegex
on Python 3 and ~py2:unittest.TestCase.assertRegexpMatches
on Python 2.
assertNotRegex()
Alias for ~py3:unittest.TestCase.assertNotRegex
on Python 3 and ~py2:unittest.TestCase.assertNotRegexpMatches
on Python 2.
six.moves
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.
Note
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 |
collections_abc |
py2:collections |
py3:collections.abc (3.3+) |
dbm_gnu |
py2:gdbm |
py3:dbm.gnu |
dbm_ndbm |
py2:dbm |
py3:dbm.ndbm |
_dummy_thread |
py2:dummy_thread |
py3:_dummy_thread (< 3.9) py3:_thread (3.9+) |
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 |
six.moves.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
six.moves.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
six.moves.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
six.moves.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
six
It is possible to add additional names to the six.moves
namespace.
add_move(item)
Add item to the six.moves
mapping. item should be a MovedAttribute
or MovedModule
instance.
remove_move(name)
Remove the six.moves
mapping called name. name should be a string.
Instances of the following classes can be passed to add_move
. Neither have any public members.
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.
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.