python ipywidges: how to pass an extra variable to a handler

user_7168098 0
Viewed 52

I would like to observe an ipywidget text input

out4 = wd.Output()
wd_input_text4 = wd.Text(value="",
                         placeholder='placeholder',
                         description='Number:',
                         )
def method4(sender):
    with out4:
        out4.clear_output()
        print(wd_input_text4.value)

wd_input_text4.observe(method4, names=['value'], type='change')

display(wd.VBox([wd_input_text4,out4]))

What I would like is to pass to the handler an extra variable, just call it A. pseudocode would be (it does not work):

def method4(sender, A):
        with out4:
            out4.clear_output()
            print(wd_input_text4.value, A)
    
    wd_input_text4.observe(method4, names=['value'], type='change', A)

Is that even possible? How can I do it?

ipywidgets python
2 Answers
class Method4:
    def __init__(self,ctx):
        self.ctx = ctx
    def method4(self, sender):
        with out4:
            out4.clear_output()
            print(wd_input_text4.value, self.ctx)

wd_input_text4.observe(Method4(A).method4, names=['value'], type='change')
user_18833160

Using functools.partial would avoid a class to hold the extra state.

import ipywidgets as widgets
import functools

a = widgets.IntText()

def observe_val(to_add, widg):
    val = widg['new']
    print(val + to_add)
    
a.observe(functools.partial(observe_val, 4), names=['value'])
display(a)
user_87312720
Related