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 and new-style classes. In Python 3, this is just new-styles.

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 intepreter 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)¶

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)

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 2.4 and 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 2.4 and 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 2.4 and 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 2.4 and 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.

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)¶

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)¶

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)¶

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)¶

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.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.

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.)

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.

ノート

Python 3’s py3:exec() doesn’t take keyword arguments, so calling exec() with them should be avoided.

six.print_(*args, *, file=sys.stdout, end="n", sep=" ")¶

Print args into file. Each argument will be separated with sep and end will be written to the file at the last.

ノート

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. :)

six.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.

six.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.

six.add_metaclass(metaclass)¶

Class decorator that replaces a normally-constructed class with a metaclass-constructed one. Unlike with_metaclass(), add_metaclass() does not create an intermediate base class between the class being created and its bases. 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__ = MyMeta

on Python 2.

Note that class decorators require Python 2.6. However, the effect of the decorator can be emulated on Python 2.4 and 2.5 like so:

class MyClass(object):
    pass
MyClass = add_metaclass(Meta)(MyClass)

Binary and text data¶

Python 3 enforces the distinction between byte strings and text strings far more rigoriously 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)¶

A “fake” bytes literal. data should always be a normal string literal. In Python 2, b() returns a 8-bit string. In Python 3, data is encoded with the latin-1 encoding to bytes.

ノート

Since all Python versions 2.6 and after support the b prefix, b(), code without 2.5 support doesn’t need b().

six.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.

ノート

In Python 3.3, the u prefix has been reintroduced. Code that only supports Python 3 versions greater than 3.3 thus does not need u().

ノート

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.

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.StringIO¶

This is an 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.

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 imp 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 appropiate 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.

Supported renames: