<p>Is there a Vim shortcut for jumping to the argument list of the current function?  I often find myself needing to mess with the argument list of a function, and it's kind of annoying to have to do ?def or ?function or 10k or what-have-you until I finally get to it, then /( or t( or 5e to get to the right position in the argument list, and so on.  It would be great if I could just hit ,a for example and instantly get put into insert mode at the end/beginning of the argument list.</p>

<p>Possible approaches:</p>

<ul>
<li>Folding</li>
<li>Tag support (ctags)</li>
</ul>

<p>Also, I'm using Python, so solutions based on curly braces unfortunately won't work.</p>

<p>If no such shortcut exists, I'll just write one and post it here as an answer.  :-)</p>

map ,a ma[{F(a
Hit ,a to go to the argument list, then `a to return to where you were when you invoked ,a. Caveat: [{ jumps back to the last unmatched { character, so if you're inside a loop or other control structure, it will take you to the beginning of that, instead.
I don't know of a way to get to the beginning of the function in a fool-proof way. If you're consistent about your tabbing, you may be able to do something like this:
map ,a ma?function :nohlf(a
where, if you don't use a single tab before you define your functions, you'd change  to appropriate value.