What’s New In Python 3.2

Author:Raymond Hettinger Release:3.2a0 Date:July 06, 2010

This article explains the new features in Python 3.2, compared to 3.1.

PEP XXX: Stub

Other Language Changes

Some smaller changes made to the core Python language are:

• Stub

New, Improved, and Deprecated Modules

• The ftplib.FTP class now supports the context manager protocol (Contributed by Tarek Ziadé and Giampaolo Rodolà; issue 4972.)

• The previously deprecated string.maketrans() function has been removed in favor of the static methods, bytes.maketrans() and bytearray.maketrans(). This change solves the confusion around which types were supported by the string module. Now, str, bytes, and bytearray each have their own maketrans and translate methods with intermediate translation tables of the appropriate type.

  (Contributed by Georg Brandl; issue 5675.)

• The previously deprecated contextlib.nested() function has been removed in favor of a plain with statement which can accept multiple context managers. The latter technique is faster (because it is built-in), and it does a better job finalizing multiple context managers when one of them raises an exception.

  (Contributed by Georg Brandl and Mattias Brändström; appspot issue 53094.)

• The shutil.copytree() function has two new options:

  • ignore_dangling_symlinks: when symlinks=False (meaning that the function copies the file pointed to by the symlink, not the symlink itself) this option will silence the error thrown if the file doesn’t exist.
  • copy_function: a callable that will be used to copy files. shutil.copy2() is used by default.

  (Contributed by Tarek Ziade.)

• The sqlite3 module has some new features:

  • XXX enable_load_extension
  • XXX load_extension
  • New Connection attribute in_transaction is True when there are uncommitted changes, and False otherwise. (Contributed by R. David Murray and Shashwat Anand, issue 8845.)

Multi-threading

• The mechanism for serializing execution of concurrently running Python threads (generally known as the GIL or Global Interpreter Lock) has been rewritten. Among the objectives were more predictable switching intervals and reduced overhead due to lock contention and the number of ensuing system calls. The notion of a “check interval” to allow thread switches has been abandoned and replaced by an absolute duration expressed in seconds. This parameter is tunable through sys.setswitchinterval(). It currently defaults to 5 milliseconds.

  Additional details about the implementation can be read from a python-dev mailing-list message (however, “priority requests” as exposed in this message have not been kept for inclusion).

  (Contributed by Antoine Pitrou.)

• Recursive locks (created with the threading.RLock() API) now benefit from a C implementation which makes them as fast as regular locks, and between 10x and 15x faster than their previous pure Python implementation.

  (Contributed by Antoine Pitrou; issue 3001.)

• Regular and recursive locks now accept an optional timeout argument to their acquire method. (Contributed by Antoine Pitrou; issue 7316) Similarly, threading.Semaphore.acquire() also gains a timeout argument. (Contributed by Torsten Landschoff; issue 850728.)

Optimizations

Major performance enhancements have been added:

• Stub

IDLE

• Stub

Build and C API Changes

Changes to Python’s build process and to the C API include:

• Stub

Porting to Python 3.2

This section lists previously described changes and other bugfixes that may require changes to your code:

• bytearray objects cannot be used anymore as filenames: convert them to bytes
• PyArg_Parse*() functions:
  • “t#” format has been removed: use “s#” or “s*” instead
  • “w” and “w#” formats has been removed: use “w*” instead