Using infinite values with DateTimeTZRange

Hi,

Apologies if this isn’t the right place to ask questions like this but I am having difficulty storing ‘infinite’ dates using the DateTimeTZRange object.

I have a Postgres database with a ‘tstzrange’ column (named validity) and I’d like to store a value in this similar to ‘[“2010-01-01 10:00:00 +01”, infinity]’.

I’m using SQL Alchemy’s ORM to store data from Python with a model containing:

```
from sqlalchemy.dialects.postgresql import TSTZRANGE
...

class Principle(Base):
__tablename__ = 'principles'

id = Column(Integer, primary_key=True)
validity = Column(TSTZRANGE())
```

And then code to generate a timestamp range, using ‘datetime.max()’ to represent infinity as mentioned here [1]:

```
from psycopg2.extras import DateTimeTZRange
...

from_now = timezone("utc").localize(datetime.now())
until_forever = timezone("utc").localize(datetime.max)

validity = DateTimeTZRange(from_now, until_forever)
```

I then added the code from [2] to translate the use of datetime.max into 'infinity' for use in Postgres, however when I
tried to save this model I got this error instead:

'argument 1 must be datetime.date, not DateTimeTZRange'

I naively tried changing this line:

```
psycopg2.extensions.register_adapter(datetime.date, InfDateAdapter)
```

to:

```
psycopg2.extensions.register_adapter(DateTimeTZRange, InfDateAdapter)
```

But that gave me the same error. I'm afraid I don't know Python or this library well enough to adapt the snippet from
[2] into a form that will work with timestamp ranges - assuming that's what I need to do?

Does anyone here from any advice for how to make this work? I did try googling, but I kept getting directed back to [2].

Thanks,
Felix.

[1] http://initd.org/psycopg/docs/extras.html#range-data-types
[2] http://initd.org/psycopg/docs/usage.html#infinite-dates-handling

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