How do I use timedelta with an input_datetime? I want to use this to get notified when certain things need to happen.
# when the filter was last changed
{% set changed = states('input_datetime.fridge_1_filter_changedate') %}
# when to get notified (elapsed days since changed date)
{% set change_days = states('input_number.fridge_1_filter_days') | int %}
{{ changed + timedelta(days=change_days) }}
Template editor show following in the output…
TypeError: can only concatenate str (not "datetime.timedelta") to str
I understand that ‘changed’ is a string.
Can I change it to a datetime so I can add some amount of time on to it? If not, what is the best approach to accomplish my goal?
Alternately, you can leverage the fact an input_datetime has a timestamp attribute. We can add change_days to it (in seconds) then convert the result to local time.
Valiant effort my friend! Thanks for your contribution. Would there be clever way to turn the datetime helpers into datetime object? Maybe a config option like the has_date: ?
No, because the State value of all entities is a string. Unless that convention changes, you can’t have datetime helpers with a State type that differs from all other entities.
However, an entity’s attributes can be other types. An enhancement would be to allow datetime helpers to have an attribute containing a proper datetime object. Assuming this new attribute was called dto, your template would look like this:
It’s wishful thinking. There’s little chance of the development team agreeing to make an input_datetime’s state type different from all other entities. The structure of the State Object is common to all entities.
A more plausible request would be to allow a state value to have different types (not only string) just like attributes can. In other words, the enhancement is for all entities, not just input_datetime. However, this would represent a monumental change. Most everything in Home Assistant that uses an entity’s state value expects the type to be string.
If you feel strongly about it, post your idea as an Issue in the GitHub Architecture repo. Discussing it here isn’t likely to reach the people who can implement it. If you do post it, it will have to be a reasoned proposal and not simply “it would be welcomed by users”. Good luck!
Coming back to this after an exchange on Discord. How would you folks feel about helpers providing an attribute whose value is equal to the state, but retaining the native type? boolean for input_boolean, float (probably) for input_number, datetime for input_datetime, etc. That way, we don’t have to worry about how states are represented, and provide simpler options for using typed values.
From the code, it’s all based on a private datetime object:
@property
def state(self):
"""Return the state of the component."""
if self._current_datetime is None:
return None
if self.has_date and self.has_time:
return self._current_datetime.strftime(FMT_DATETIME)
if self.has_date:
return self._current_datetime.strftime(FMT_DATE)
return self._current_datetime.strftime(FMT_TIME)
And it looks like it does start with today at 00:00:
If a timedelta is based on today, does that mean it cannot handle 24 hours or more? Because if it is supposed to handle more than 24 hours (which I hope) a timedelta will suddenly change value at midnight. The whole point of having a timedelta type is because people should realize a timestamp is not a duration of time. If you want to (mis)use a timestamp it, the offset should be a constant.
