Access return value of functions

[DeCabMax]

Question

Hi,
i want to read the the return variable of a function that is triggerd by ui.button.
How do i access the returned variable. z.value doesnt work because z is a button and have no value.

def function(x,y):
    return_v1 = np.sqrt(x**2 + y**2 )
    return return_v1

x =  ui.number(label='x',format='%.4f', value = 0)
y =  ui.number(label='x',format='%.4f', value = 0)

z = ui.button(on_click= lambda e:function_1(x.value,y.value))

ui.label(      )
##          A
##          |
## here i want to show the return value 

[rodja]

Straying a bit further away from your code, I would do it with bindings:

@dataclass
class Coordinate:
    x: float
    y: float

    @property
    def z(self) -> float:
        return np.sqrt((self.x or 0)**2 + (self.y or 0)**2)

c = Coordinate(0, 0)
ui.number(label='x', format='%.4f').bind_value(c, 'x')
ui.number(label='y', format='%.4f').bind_value(c, 'y')
ui.label().bind_text_from(c, 'z', backward=lambda z: f'z={z:.4f}')

[falkoschindler]

Regarding the original question: Note that when ui.label is placed on the page, the button hasn't been clicked and the function hasn't been executed yet. Therefore there is no return value at this moment.

To update the label, you can use binding like in @rodja's answer. Or you let the event handler update the label:

def function_1(x: float, y: float):
    z.text = f'{np.sqrt(x**2 + y**2):.4f}'

x = ui.number(label='x', format='%.4f', value=0)
y = ui.number(label='y', format='%.4f', value=0)
ui.button('Compute', on_click=lambda: function_1(x.value, y.value))

z = ui.label()

[rohitsathish]

How would this approach be applied for tables @falkoschindler? As I understand, you can't have an empty instantiation of a table.

[falkoschindler]

I think this is being discusses over at #2098.