linking jupyter widget text box to a function plotting a graph - function

Question

I am trying to construct a user interface in Jupyter notebook that is able to link one function with a text widget and button widget.
My function creates a plot for the stock price of a given stock from a start date to end date. The functions is as follow
import pandas_datareader as pdr
from datetime import datetime
def company(ticker):
strt=datetime(2020,1,1)
end=datetime.now()
dat=pdr.get_data_yahoo(ticker, strt, end)
return dat['Close'].plot(grid=True)
The following command plots apple stock price.
company('AAPL')
Now i create a text and button widget as follow
import ipywidgets as ipw
box=ipw.Text(
value='Stock handle',
placeholder='Type something',
description='String:',
disabled=False)
btn=ipw.ToggleButton(
value=False,
description='Plot',
disabled=False,
button_style='', # 'success', 'info', 'warning', 'danger' or ''
tooltip='Description',
icon='check' # (FontAwesome names without the `fa-` prefix))
I tried to link the function company with box as follow:
box.on_submit(company)
When I write AAPL in box it gives me error "TypeError: object of type 'Text' has no len()
"
My goal is to create an interface where i write the name of the stock('AAPL') in the box and click the btn at which point the plot of the stock price will appear.
Any help is appreciated. Thank you.

Answer 1

When you attach a function with on_submit, the entire widget gets passed as the argument to the function (not just the text value). So within your company function, ticker is actually your instance of the Text widget. Hence the error, as you cannot call len on a widget.
To get the text value of the widget, use ticker.value, which you should be able to call len on just fine.
def print_it(ticker):
# print(len(ticker)) # raises TypeError, you're calling len on the Text widget
print(len(ticker.value)) # will work, as you're accessing the `value` of the widget which is a string
t = ipywidgets.Text(continuous_update=False)
t.on_submit(print_it)
t
NB. the on_submit method is deprecated as of ipywidgets 7.0, much better to create your box using use box.observe(), and when you create your box include continuous_update=False as a kwarg. With this method, a dictionary of info gets passed to your function, so you need to parse out the new value and print it.
def print_it(ticker):
print(ticker['new']) # will work, as you're accessing the string value of the widget
t = ipywidgets.Text(continuous_update=False)
t.observe(print_it, names='value')
t