About new release - Python 3.3.0

The new Python 3.3.0 was released on September 29th, 2012.

It's been two weeks since it was launched last version of python and I don't have found complaints about this release.

We can read more about updates and changes made by developers here.

What I think it's more significantly to this version:

• The new "faulthandler" module that helps diagnosing crashes
• The new "unittest.mock" module
• The new "ipaddress" module
• The "sys.implementation" attribute
• A policy framework for the email package, with a provisional (see PEP 411) policy that adds much improved unicode support for email header parsing
• A "collections.ChainMap" class for linking mappings to a single unit
• Wrappers for many more POSIX functions in the "os" and "signal" modules, as well as other useful functions such as "sendfile()"
• Hash randomization, introduced in earlier bugfix releases, is now switched on by default
• A C implementation of the "decimal" module, with up to 120x speedup for decimal-heavy applications
• The import system (__import__) is based on importlib by default
• The new "lzma" module with LZMA/XZ support
• PEP 397, a Python launcher for Windows
• PEP 405, virtual environment support in core

Let's see how to working the new Python 3.3.0

First download it , unzip and install it. See next:

/Python-3.3.0 $ ./configure 
checking build system type... i686-pc-linux-gnu
checking host system type... i686-pc-linux-gnu
checking for --enable-universalsdk... no
checking for --with-universal-archs... 32-bit
checking MACHDEP... linux
checking for --without-gcc... 

The next step is ...

$ make all

And finally ...

# su 
# ./python setup.py build
running build
running build_ext
INFO: Can't locate Tcl/Tk libs and/or headers

Python build finished, but the necessary bits to build these modules were not found:
_bz2               _dbm               _gdbm           
_lzma              _sqlite3           _ssl            
_tkinter           readline                           
To find the necessary bits, look in setup.py in detect_modules() for the module's name.

I will use it without this modules, until I find a way to fix it.

$ ./python 
Python 3.3.0 (default, Oct 14 2012, 21:42:00) 
[GCC 4.4.1] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 
>>> import ipaddress

Tuples can put you in difficulty.

They are two examples of sequence data types in python.

Today I will tell about tuples.

A tuple consists of a number of values separated by commas.

The biggest problem is when we do not know the number of these values ​​or type.

Let me illustrate with a function that returns a tuple.

This is a known tuple but we will use like an unknown tuple.

Let's see the python code and some errors:

>>> import sys
>>> if hasattr(sys, 'version_info'):
...     print sys.version_info()
... 
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
TypeError: 'tuple' object is not callable

Is very correct to got this error.

And the result using the print function:

>>> if hasattr(sys, 'version_info'):
...     print "%s" % str(sys.version_info)
... 
(2, 6, 4, 'final', 0) 

>>> if hasattr(sys, 'version_info'):
...     sys.stderr.write("%s" % str(sys.version_info))
... 
(2, 6, 4, 'final', 0)>>> 

or if you can use the repr function.

>>> if hasattr(sys, 'version_info'):
...     sys.stderr.write("%s" % repr(sys.version_info))
... 
(2, 6, 4, 'final', 0)>>> 

The official Python documentation says __repr__ is used to compute the “official” string representation of an object and __str__ is used to compute the “informal” string representation of an object.

In my opinion , the correct way it's to use repr. For example:

>>> import datetime
>>> today = datetime.datetime.now()
>>> str(today)
'2012-10-02 22:45:57.634977'
>>> repr(today)
'datetime.datetime(2012, 10, 2, 22, 45, 57, 634977)'

As we see all values from tuples it's show.

Setting up Vim to work with Python - part 2

You can customize Vim for editing a specific file.

In this case is our python script files.

To do that you can use modelines, or auto commands, or filetype plugins.

For example , if you want to see the number on rows then just set the boolean number option to true.

set number

The keys PageUp and PageDown are mapped to Ctr+U and Ctr+D.

The next changes of the vimrc file will move cursor only by half of screen.

map <PageUp> <C-U>
map <PageDown> <C-D>
imap <PageUp> <C-O><C-U>
imap <PageDown> <C-O><C-D>

To move the cursor to the end of the screen they have to be triggered twice:

map <PageUp> <C-U><C-U>
map <PageDown> <C-D><C-D>
imap <PageUp> <C-O><C-U><C-O><C-U>
imap <PageDown> <C-O><C-D><C-O><C-D>

Then you can add next line to prevent the cursor from changing the current column when jumping to other lines within the window.

set nostartofline

To add some lines on your python file.

For example many python files start with this:

#!/usr/bin/env python 
#-*- coding: utf-8 -*-

Just add the next line in your vimrc file.

:iabbrev newpy  #!/usr/bin/env python <cr>#-*- coding: utf-8 -*-

On your first line from your python file in the insert mode , write newpy and press Enter key.

Also will be a good idea to take a look at the official .vimrc for following PEP 7 & 8 conventions.

...and the result of this changes.