dcc.DatePickerSingle() persistence not working

[jezlax]

I'm on dcc 1.5.1 ... I have a date picker single which populates a date using the following...

dcc.DatePickerSingle(className = 'no-print', id='choose-date', date = datetime.today() - timedelta(hours=7), persistence=True, persistence_type='session')

however the persistence does not take. In this example, the date picker populates a set of links (html.A()) elements for the given date. The user then selects the link of choice to populate the remainder of the charts on the app.

While the date picker works fine, when the user selects the link, it triggers an HREF callback and the date picker resets to the default date. My goal is to have the date persist until the user exits the page.

[alexcjohnson]

Thanks for the report, investigating... that said, since the link is to a different view within the same dash app you may be able to do this more easily using dcc.Link and dcc.Location https://dash.plot.ly/urls and leaving the date picker outside the part of the page that's changed.

[alexcjohnson]

@jezlax I'm guessing this DatePickerSingle component is generated either in a layout function or in a callback - ie datetime.today() - timedelta(hours=7) is changing every time it's called because it goes all the way to microseconds - it gets serialized something like date: "2019-11-14T14:45:12.741865". This is a problem for persistence because we'll only reapply the user's choice if the initial value provided with the component is the same as before the user made that choice.

If you strip out the (unused) time portion - something like (datetime.today() - timedelta(hours=7)).date() - then it will give a consistent value for 24 hours - so if the user keeps the app open for multiple days it'll reset (on reload) once a day, but the persistence should be maintained until that point.

[jezlax]

Thanks @alexcjohnson - I will dev this rework today and let you know.