Development tools and practices for Pythonistas

[snorble]

I'm not a Pythonista, but I aspire to be.

My current tools:

Python, gvim, OS file system

My current practices:

When I write a Python app, I have several unorganized scripts in a
directory (usually with several named test1.py, test2.py, etc., from
random ideas I have tested), and maybe a todo.txt file. Then I hack
away, adding features in a semi-random order. Then I get busy with
other things. Maybe one week I spend 20 hours on development. The next
week, no time on development. A few weeks later when I have some time,
I'm excited to get back to making progress, only to find that I have
to spend 30-60 minutes figuring out where I left off. The code is
usually out of sync with todo.txt. I see people who release new
versions and bug fixes, so I sometimes will create a new directory and
continue working from that copy, because it seems like the thing to
do. But if I ever made something worth releasing, and got a request
like, "I have problems with the 2.0 version. Can you send me the old
1.1 version?" I'd be like, "uhhh... let me hunt through my files by
hand and get back to you in a month". I'm thinking I can do a lot
better than this.

I am aware of tools like version control systems, bug trackers, and
things like these, but I'm not really sure if I need them, or how to
use them properly. I think having some organization to all of this
would help me to make more consistent progress, and spend less time
bringing myself up to speed after some time off.

I really like the idea of having a list of features, and tackling
those features one at a time. I read about people who do this, and
each new features gets a new minor version number. It sounds very
organized and clean. But I'm not really sure of the best way to
achieve this. Mainly I think I just need some recommendations to help
create a good mental map of what needs to happen, and mapping jargon
to concepts. Like, "each feature gets its own directory". Or with a
version control tool, I don't know if a feature maps to a branch, or a
commit?

I appreciate any advice or guidance anyone has to offer.