Author: | A.M. Kuchling (amk at amk.ca) |
---|---|
Release: | 3.1a1 |
Date: | March 07, 2009 |
This article explains the new features in Python 2.7. No release schedule has been decided yet for 2.7.
Some smaller changes made to the core Python language are:
The int() and long() types gained a bit_length method that returns the number of bits necessary to represent its argument in binary:
>>> n = 37
>>> bin(37)
'0b100101'
>>> n.bit_length()
6
>>> n = 2**123-1
>>> n.bit_length()
123
>>> (n+1).bit_length()
124
(Contributed by Fredrik Johansson and Victor Stinner; issue 3439.)
A few performance enhancements have been added:
As in every release, Python’s standard library received a number of enhancements and bug fixes. Here’s a partial list of the most notable changes, sorted alphabetically by module name. Consult the Misc/NEWS file in the source tree for a more complete list of changes, or look through the Subversion logs for all the details.
In Distutils, distutils.sdist.add_defaults now uses package_dir and data_files to feed MANIFEST.
It is not mandatory anymore to store clear text passwords in the .pypirc file when registering and uploading packages to PyPI. As long as the username is present in that file, the distutils package will prompt for the password if not present. (Added by tarek, with the initial contribution of Nathan Van Gheem; issue 4394.)
The bz2 module’s BZ2File now supports the context management protocol, so you can write with bz2.BZ2File(...) as f: .... (Contributed by Hagen Fuerstenau; issue 3860.)
A new Counter class in the collections module is useful for tallying data. Counter instances behave mostly like dictionaries but return zero for missing keys instead of raising a KeyError:
>>> from collections import Counter
>>> c=Counter()
>>> for letter in 'here is a sample of english text':
... c[letter] += 1
...
>>> c
Counter({' ': 6, 'e': 5, 's': 3, 'a': 2, 'i': 2, 'h': 2,
'l': 2, 't': 2, 'g': 1, 'f': 1, 'm': 1, 'o': 1, 'n': 1,
'p': 1, 'r': 1, 'x': 1})
>>> c['e']
5
>>> c['z']
0
There are two additional Counter methods: most_common() returns the N most common elements and their counts, and elements() returns an iterator over the contained element, repeating each element as many times as its count:
>>> c.most_common(5)
[(' ', 6), ('e', 5), ('s', 3), ('a', 2), ('i', 2)]
>>> c.elements() ->
'a', 'a', ' ', ' ', ' ', ' ', ' ', ' ',
'e', 'e', 'e', 'e', 'e', 'g', 'f', 'i', 'i',
'h', 'h', 'm', 'l', 'l', 'o', 'n', 'p', 's',
's', 's', 'r', 't', 't', 'x']
Contributed by Raymond Hettinger; issue 1696199.
The gzip module’s GzipFile now supports the context management protocol, so you can write with gzip.GzipFile(...) as f: .... (Contributed by Hagen Fuerstenau; issue 3860.)
The io.FileIO class now raises an OSError when passed an invalid file descriptor. (Implemented by Benjamin Peterson; issue 4991.)
The pydoc module now has help for the various symbols that Python uses. You can now do help('<<') or help('@'), for example. (Contributed by David Laban; issue 4739.)
A new function in the subprocess module, check_output(), runs a command with a specified set of arguments and returns the command’s output as a string if the command runs without error, or raises a CalledProcessError exception otherwise.
>>> subprocess.check_output(['df', '-h', '.'])
'Filesystem Size Used Avail Capacity Mounted on\n
/dev/disk0s2 52G 49G 3.0G 94% /\n'
>>> subprocess.check_output(['df', '-h', '/bogus'])
...
subprocess.CalledProcessError: Command '['df', '-h', '/bogus']' returned non-zero exit status 1
(Contributed by Gregory P. Smith.)
The is_zipfile() function in the zipfile module will now accept a file object, in addition to the path names accepted in earlier versions. (Contributed by Gabriel Genellina; issue 4756.)
Tcl/Tk 8.5 includes a set of themed widgets that re-implement basic Tk widgets but have a more customizable appearance and can therefore more closely resemble the native platform’s widgets. This widget set was originally called Tile, but was renamed to Ttk (for “themed Tk”) on being added to Tcl/Tck release 8.5.
XXX write a brief discussion and an example here.
The ttk module was written by Guilherme Polo and added in issue 2983. An alternate version called Tile.py, written by Martin Franklin and maintained by Kevin Walzer, was proposed for inclusion in issue 2618, but the authors argued that Guilherme Polo’s work was more comprehensive.
Changes to Python’s build process and to the C API include:
This section lists previously described changes and other bugfixes that may require changes to your code:
To be written.
The author would like to thank the following people for offering suggestions, corrections and assistance with various drafts of this article: no one yet.