Support reading other properties than value?

[bryceschober]

Now my problem is that I want to use it with from ipyfilechooser import FileChooser, which doesn't inherit from ValueWidget or have a value property or something:

/opt/conda/lib/python3.7/site-packages/ipython_blocking/ipython_magic.py in block(self, line)
     57             func = lambda: obj._has_been_clicked
     58         else:
---> 59             raise Exception('The positional argument to %block should be a ValueWidget, Button, or a function/method')
     60         return self.capture(func, args.timeout)
     61 

If there were some way to point at a property: %block myobject.property, and somehow introspect that it was indeed a value or property to do change detection on, then it could be a good general-purpose solution. Also, FileChooser should probably actually inherit and provide a value, but that's another matter.

Yes, I know I can write a change-detecting function, as per the workaround in #5:

# previous cell
config_selector = FileChooser(str(root_working_dir), use_dir_icons=True)
display(config_selector)

# next cell
ctx = ipython_blocking.CaptureExecution()
with ctx:
    init_val = config_selector.selected
    while True:
        if init_val != config_selector.selected:
            break
        ctx.step()

...but I was hoping for an easy-to-read magic one-liner.

[bryceschober]

@kafonek After I requested it, ipyfilechooser now inherits from ValueWidget and implements get_interact_value(), but that seems to not be enough for ipython_blocking...

[kafonek]

@bryceschober for any kind of situation where you're working with non-standard widgets or have some complex validation (like multiple widgets being filled out), the best thing to do with ipython_blocking is define a function to block on. Basically at every step (kernel.do_one_iteration()) it will run your blocking function. If the function returns True, it breaks out of the blocking context. If not, it stays in the blocking context.

For FileChooser, try this out:

### cell 1
import ipyfilechooser
fc = ipyfilechooser.FileChooser()

def block_until_selected():
    return bool(fc.selected)

fc

### cell 2
import ipython_blocking

%block block_until_selected

### cell 3
### will not run until a file is selected in cell 1
fc.selected

[bryceschober]

Yep, that ended up being simpler, thanks.