xonsh: Is there a way to call a function as a command that takes optional arguments?

Question

I have a function in Xonsh that I'm trying to use like a command (ie: without parens). The function should optionally take arguments, however whenever I call the function without arguments, I just get the function address. How do you call a function with optional parameters?

Here's the example:

def _up(args, stdin=None):
    # go up any number of directories
    if not args or len(args) < 1:
        args[0] = 1
    balloons = ('../' * int(args[0]))
    # echo @(balloons)
    cd @(balloons)
aliases['up'] = _up

When I call up with no parameters, I get <function __main__.up>. When I call it like this, it works: up 2.

I could do a function like this that works, but then I can't call it without using parentheses (ie: as a command) which is what I'd prefer:

def up(dirs=1):
    # go up any number of directories
    balloons = ('../' * dirs)
    # echo @(balloons)
    cd @(balloons)

Calling up() and up(2) both work this way, but is more cumbersome than just calling up or up 2. What's the right way to accomplish what I'm trying to do in Xonsh?

Answer 1

I'm not certain why you're getting the function repr when you aren't passing in an argument, but a tweaked version of your function works:

def _up(args):  # don't need stdin
    # go up any number of directories
    if not args or len(args) < 1:
        args = [1]  # if args is None you can't index to it
    balloons = ('../' * int(args[0]))
    # echo @(balloons)
    cd @(balloons)
aliases['up'] = _up

on current-ish main of xonsh @ c2f862df this works to go up one level with just an up or you can specify many levels with up 3, etc.