That's a good question.

In fact, txt2tags 2.5 is still compatible with Python 1.5.2. We broke that in 
SVN and now this is open to discussion.

I prefer txt2tags to be compatible with oldest Python versions whenever 
possible. There's no reason to break compatibility for guys unfortunately stuck 
with old Python versions.

Now (2010) Python 1.5.2 is really really old. Python 3 is too fresh (and breaks 
compatibility with 2.x).

I still don't have an answer for that, but I do prefer to stick with 2.x, where 
x is the lowest possible number :)

http://txt2tags.sourceforge.net/changelog.html

Version 2.5 (2008-07-26)

# IMPORTANT: Txt2tags is not compatible with old Python 1.5.2 anymore, because 
Unicode strings were added in Python 2.0. If your Python is older than 2.0, 
please use txt2tags version 2.4. 

Oops, I don't remember important facts of my own program. Thanks for correcting 
me Florent! :)

Thinking more about it, txt2tags 2.5 requires Python 2.0. The planned 
break-everything txt2tags 3.0 release will be Python 3 compatible.

Now we're in the middle of this change. I don't think it will be nice to our 
users breaking compat now in txt2tags 2.6 and then again in 3.0.

We can hold on and not use newer features, trying to stick with Python 2.0, so 
users of txt2tags 2.5 can safely upgrade to 2.6. When the time to upgrade to 
Python 3 comes, we do use all the new features.

How about it?

The question is "do people still using python 2.0 really need the new features 
of txt2tags on their system?"

I guess the txt2tags 2.5 version is good enough for converting to LaTeX, html 
and such, and in the case someone for example needs to process files 
automatically on a server, the distributions probably won't propose the newest 
version of txt2tags. 

Linux Debian Lenny which is already quite old is using python 2.5 and for older 
versions there are some backports for installing newer version for example. On 
Mac OS X, there is an installer of python-2.5.1-macosx.dmg which is suitable 
for Panther (10.3), and on Windows it's easy to get the latest version of 
python.

And even if people have issues with the 2.0 version of python being too old, it 
won't prevent to open and work on the txt2tags files, and convert their work on 
an other computer ;)

I don't think it's "breaking compat". For my code, Python 2.3 seems a need.
But the older Python I know on a real computer is 2.4, so I think it's not an 
issue.

Python2.0 2000 txt2tags2.5 2008 : 8 years safe.
Python2.3 2003 txt2tags2.6 2010 : 7 years safe.
It sounds ok for me.

With r174 et r175, trunk is now Python2.3 ready.

The only 2.3 feature is one "enumerate()" in the aa_table function...but it's 
only used with the %!csv command, and there's no csv support in Python lib 
before Python 2.3 !

So as it is, txt2tags is Python2.2 ready.

Great job Florent, now we don't have Python version issues anymore, yay!

I don't have Python 2.0 or 2.1 here to test, so maybe we're 2.0 ready too.

I'll let this issue open, so we can continue the discussion about Python 
version for future releases.

AA = dict(zip(AA_KEYS, AA_VALUES)) seems to be the only one problem.

Python 2.0 :
Traceback (most recent call last):
  File "txt2tags", line 206, in ?
    AA = dict(zip(AA_KEYS, AA_VALUES))
NameError: There is no variable named 'dict'

Python 2.1 same error (more a warning):
txt2tags:5654: SyntaxWarning: local name 'name' in 'target_name2key' shadows 
use of 'name' as global in nested scope 'lambda'
  def target_name2key(self):
Traceback (most recent call last):
  File "txt2tags", line 206, in ?
    AA = dict(zip(AA_KEYS, AA_VALUES))
NameError: name 'dict' is not defined

In r340 os.path.relpath() was used, but it is a Python 2.6 feature.

It fixes the relative image path problem, when using include files on different 
folders, or when output file is in a different folder.

But it bumps our minimum requirements, which today is Python 2.3.

Close to txt2tags-2.7 release, check if it's the only new command used. If so, 
search for substitutes.

New module used since r491 : textwrap, new in Python 2.3.

New module 'email' since r530, new in Python 2.2.

Since r550 using key in dic instead dic.has_key(key).

dic.has_key() is deprecated since Python 2.6.
key in dic was introduced in Python 2.3.

r556 to simplify csv import.

Ok, let's raise the bar and set Python 2.3 as the minimum required version for 
the next txt2tags 2.7.

r676 makes Python 2.3 OK again, but what about Issue 61 ?

The CJK support with the unicodedata.east_asian_width() function requires 
Python 2.4.

r803 needs Python 2.4 too.

r827 needs Python 2.5.

r1124 needs Python 2.5 too (sqlite3 module, as r827).