I had to explicitly set the locale to Turkish since that isn't the default on my computer, but it seems to more-or-less work:
> python
Python 2.7.2 (default, Jun 12 2011, 15:08:59) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from locale import LC_ALL, setlocale
>>> print setlocale(LC_ALL,"Turkish")
Turkish_Turkey.1254
>>> from string import letters
>>> print letters
abcdefghijklmnopqrstuvwxyzƒsoªµºßàáâaäåæçèéêëìíîïgñòóôoöoùúûüisÿ...
ABCDEFGHIJKLMNOPQRSTUVWXYZSOYAAAAÄÅÆÇEÉEEIIIIGÑOOOOÖOUUUÜIS
>>>
The output basically looks correct (AFAIK) except for the inclusion of Q, W, and X, which from what's in this Wikipedia article aren't part of the Turkish alphabet.
Update:
To better replicate your environment, I first used the "Regional and Language Options" control panel and changed my region to "Turkish", which should make it the default for setlocale
. Indeed it did however the list of letters still looks OK — so I can't reproduce your problem.
One difference this time is that before running python I first changed to console's code page to Windows ANSI Turkish 1254 to enable the correct display of character from the alphabet. This made the last two letters of the output display correctly, however it also still includes the Q, W, and X letters which aren't part of the alphabet (and wrong to be there, in my option).
C:\>chcp 1254
Active code page: 1254
C:\>python
Python 2.7.5 (default, May 15 2013, 22:43:36) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from locale import LC_ALL, setlocale
>>> print setlocale(LC_ALL,"")
Turkish_Turkey.1254
>>> from string import letters
>>> print letters
abcdefghijklmnopqrstuvwxyzƒšœªµºßàáâãäåæçèéêëìíîïğñòóôõöøùúûüışÿ...
ABCDEFGHIJKLMNOPQRSTUVWXYZŠŒŸÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏĞÑÒÓÔÕÖØÙÚÛÜİŞ
>>>