Python - Version overview.md

Python version overview

Python 3.x is the current branch with active development. Python 2.x is still maintained, but without adding new features.

This is a summary of major new features in recent Python versions (thousands of bug fixes, small and parser/C API/internals/performance enhancements are not mentioned):

• Python 3.x
  • Python 3.6 · What’s New In Python 3.6
    • currently (2015-08-07) in beta phase
      • 3.6.0a0 released 2015-10-20
      • 3.6.0b4 released 2016-11-07
    • f-strings: x = "world"; y = 42; print(f"Hello {x}, {y}")
    • underscores in numbers: 10_000_000
    • __fspath__ protocol for pathlib
    • new module secrets
    • local time disambiguation: datetime(..., fold=1)
    • development moving to Github
  • Python 3.5 · What’s New In Python 3.5
    • 3.5.0 released 2015-09-13
    • math.isclose(), cmath.isclose() for approximate equality test
    • removed .pyo files
    • new matrix multiplication operator: a @ b
    • coroutines with async and await syntax
    • additional unpacking generalizations: [1, *(2, 3)] == [1, 2, 3]
    • added % formatting to byte and bytearray (not just str)
    • new methods bytes.hex(), bytearray.hex() and memoryview.hex()
    • new subprocess.run()
    • new modules:
      • typing - type hints
      • zipapp - improving Python ZIP application support
    • SSLv3 is disabled
    • automatic retry of system calls failed with EINTR
    • performance optimizations: collections.OrderedDict, os.scandir(), functools.lru_cache()
  • Python 3.4 · What’s New In Python 3.4
    • 3.4.0 released 2014-03-16
    • C files preprocessor "Argument Clinic"
    • pip command should always be available
    • newly created file descriptors non-inheritable
    • new modules:
      • asyncio for asynchronous I/O
        • deprecates asyncore and asynchat
      • ensurepip
      • enum
      • pathlib with Path object for nice path abstraction
      • selectors for I/O multiplexing
      • statistics
      • tracemalloc
  • Python 3.3 · What’s New In Python 3.3
    • yield from for generator delegation
    • u'unicode' syntax is accepted again for str objects
    • venv for virtual environments
    • new modules:
      • faulthandler
      • ipaddress
      • lzma
      • unittest.mock
      • venv
  • Python 3.2 · What’s New In Python 3.2
    • stable ABI
    • logging dictionary-based configuration
    • .pyc files stored in __pycache__ directory
    • WSGI v1.0.1, PEP 3333
    • new modules:
      • argparse for command line parsing
      • concurrent.futures
  • Python 3.1 · What’s New In Python 3.1
    • collections.OrderedDict
    • format specifier for thousands separator: format(1234567.89, ',.2f') -> '1,234,567.89'
    • directories and zip archives containing a __main__.py file can now be executed directly by passing their name to the interpreter
    • fields in format() strings can now be automatically numbered: 'Sir {} of {}'.format('Gallahad', 'Camelot')
      • formerly, the string would have required numbered fields such as: 'Sir {0} of {1}'
    • with statement now allows multiple context managers in a single statement: with open('mylog.txt') as infile, open('a.out', 'w') as outfile: ...
  • Python 3.0 · What’s New In Python 3.0
    • also known as "Python 3000" or "Py3K"
    • first ever intentionally backwards incompatible Python release
    • (some of 3.0 features are already present in Python 2.6)
    • print is a function
    • <int>/<int> returns float; use <int>//<int> for integer division
    • no long, only int (even big numbers)
    • dict.keys(), dict.values(), dict.items() return "views" instead of lists
      • dict.iterkeys(), dict.itervalues(), dict.iteritems() gone
    • range() returns a special object instead of list, xrange() gone
    • sorted() and list.sort() no longer accepts cmp agument, use key instead
    • Text vs bytes:
      • str is the new unicode
      • b'...' for binary data, 'foo' for strings
      • str and bytes objects cannot be mixed (like unicode and str in 2.x)
      • bytes is immutable, bytearray is mutable
    • nonlocal keyword
    • unpacking: a, b, *rest = some_sequence
    • dictionary compehensions: {k: v for k, v in stuff}
    • set literals: {1, 2, 3}
    • set comprehensions
    • except Exception, var forbidden (use except Exception as var)
    • True, False and None are reserved keywords
    • metaclasses and __metaclass__
    • ellipsis: ... can be used anywhere, not only in slices
    • super()
    • old-style classes gone, all classes are new-style
    • raw_input() renamed to input()
    • reload() removed, use imp.reload()
    • some modules renamed or restructured
    • "It is not recommended to try to write source code that runs unchanged under both Python 2.6 and 3.0" - this opinion changed in later 3.x versions :) It was expected to use the tool 2to3.
    • BTW. most problems with porting from 2.x to 3.x were unicode/str/bytes related, for example in case of WSGI
• Python 2.x
  • Python 2.7 · released 2010-07-03 · What’s New in Python 2.7
    • last of the 2.x releases, with long-term support
    • Python 3.1 features backported to 2.7:
      • set literals: {1, 2, 3}
      • dictionary and set comprehensions: {i: i*2 for i in range(3)}
      • multiple context managers in a single with` statement
      • io library rewritten in C for performance
      • memoryview object
      • subset of importlib
    • collections.OrderedDict, collections.Counter
    • logging: dictionary-based configuration
    • dict views viewskeys(), viewvalues() and viewitems()
    • PYTHONWARNINGS env variable
    • subprocess.check_output()
    • weakref.WeakSet
    • new modules:
      • argparse
      • sysconfig from Distutils
  • Python 2.6 · released 2008-10-01 · What’s New in Python 2.6
    • prepares the migration path to Python 3.0
    • backported from 3.0:
      • __complex__() magic method for converting objects to a complex number
      • alternative syntax: except Exception as e
    • command-line switch -3 enables warnings about features removed in Python 3
    • Python development process:
      • new issue tracker Roundup
      • Sphinx and reStructuredText
    • str.format(): 'user: {0} {desc}'.format('foo', name='bar')
    • print as function (optional)
    • bytes, bytearray
    • from __future__ import unicode_literals
    • octal and binary integer literals: 0o21, 0b1011
    • class decorators
    • collections.namedtuple(typename, fieldnames)
    • new packages:
      • abc - abstract base classes
      • ast - Abstract Syntax Tree representation of Python code
      • fractions
      • io
      • json
      • multiprocessing
      • plistlib for parsing Mac OS X .plist files
      • ssl
    • deprecated modules:
      • md5
      • sets
      • sha
  • Python 2.5 · released 2006-09-19 · What’s New in Python 2.5
    • conditional expressions: x = 'foo' if something else 'bar'
    • with statement: with open('/etc/passwd') as f: print f.read()
      • context management protocol - new magic methods:
        • __enter__()
        • __exit__(exc_type, exc_value, traceback)
    • absolute and relative imports: from .foo import bar
    • unified try/except/else/finally
    • generator enhancements
      • yield is now expression and returns value
      • new GeneratorExit exception
    • new __index__() magic (special) method
    • new built-in functions: any(), all()
    • new modules:
      • cProfile
      • contextlib
      • ctypes for calling C functions from Python
      • functools
      • hashlib
      • msilib for creating Microsoft Installer .msi and CAB files
      • spwd for accessing shadow password database
      • sqlite3 - SQLite database
      • uuid for creating universally unique identifiers (UUIDs)
      • wsgiref
      • xml.etree
  • Python 2.4 · released 2005-03-30 (2.4.1) · What’s New in Python 2.4
    • function and method decorators: @classmethod, @property etc.
    • generator expressions: (item for item in items if item.good())
    • built-in set objects set() and frozenset()
    • string.Template
    • reversed()
    • None is a constant, cannot be assigned a new value
    • new modules:
      • collections
      • cookielib
      • decimal with Decimal data type
      • subprocess
  • Python 2.3 · released 2003-07-29 · What’s New in Python 2.3
    • source code encoding header: # -*- coding: UTF-8 -*-
    • importing modules from ZIP archives
    • universal newline support
    • enumerate()
    • True, False
    • extended slices: L = range(10); L[::2]
    • new built-in function sum(iterable, start=0)
    • assert statement no longer checks the __debug__ flag
    • new types in datetime module: date, time and datetime
    • new modules and packages:
      • bz2
      • csv
      • itertools
      • logging
      • optparse
      • sets with Set() - new data type for mutable sets
      • tarfile
      • textwrap
      • timeit
  • Python 2.2 · released 2001-12-21 - 2002-10-14 (2.2.2) · What’s New in Python 2.2
    • any built-in type can be subclassed (including integers)
    • old-style and new-style classes
      • new-style classes are subclassed from other new-style classes or from object class C (object): pass
    • descriptors
      • objects that live inside class objects, and have a few attributes of their own:
        • __name__ is the attribute’s name.
        • __doc__ is the attribute’s docstring.
        • __get__(object) is a method that retrieves the attribute value from object.
        • __set__(object, value) sets the attribute on object to value.
        • __delete__(object, value) deletes the value attribute of object
      • For example, when you write obj.x, the steps that Python actually performs are: descriptor = obj.class.x descriptor.get(obj)
    • static methods: staticmethod()
    • class methods: classmethod()
    • properties: property()
    • slots: __slots__
    • generators: yield keyword
    • iterators: iter(obj), __iter__() method, StopIteration exception
    • multiple inheritance and diamond rule
    • __getattribute__(attr_name) (new-style classes)
    • socket with support for IPv6
    • new module hmac
  • Python 2.1 · released 2001-04-17 · What’s New in Python 2.1
    • Python Software Foundation (PSF) founded
    • Python Enhancement Proposals (PEPs) introduced in development process
    • statically nested scopes (optional in 2.1)
    • __future__ directives, for example from __future__ import nested_scopes
    • Python classes can overload operators <, <=, >, >=, ==, != using magic methods __lt__(), __le__() etc.
    • warnings module, warning framework
    • weakref module for weak references
    • function attributes def f(): pass f.foo = 42
    • sys.displayhook(), sys.excepthook()
  • Python 2.0 · released 2000-10-16 · What’s New in Python 2.0
    • core development team moved from CNRI to BeOpen
    • Unicode strings (u'čau', u'\u010dau')
    • list comprehensions: [s for s in items if s.startswith('foo')]
    • assignment operators: +=, -=, *= etc.
    • string methods: 'joe'.capitalize()) instead of string.capitalize('joe') from string module
    • garbage collection supports cycles (instance.myself = instance)
    • f(*args, **kwargs) instead of apply(f, args, kwargs)
    • print stream redirection: print >> sys.stderr, 'Hello'
    • dict.setdefault(key, default)
    • new packages: distutils, xml, gettext, mmap and other

You can almost learn Python just from this summary :)

Links:

• https://docs.python.org/dev/whatsnew/
• https://docs.python.org/dev/whatsnew/changelog.html