aapy

Python code to retrieve data from the EPICS Archiver Appliance.

Usage

Note on timezones

When you pass a datetime to aapy it doesn't know by default what timezone that datetime is supposed to be in. It will assume that it is the local timezone, but will print a warning. If you pass it a timezone-aware datetime no warning will be printed. You can use utc_datetime() as a shortcut:

>>> from aa.utils import utc_datetime
>>> utc_datetime(2019, 10, 7, 17) # 5pm UTC on 7th October 2019

Fetching data

To retrieve data, create the appropriate fetcher

>>> from aa.js import JsonFetcher
>>> jf = JsonFetcher('archappl.diamond.ac.uk', 80)

You can request a single event, returning an ArchiveEvent object:

>>> from datetime import datetime
>>> event = jf.get_event_at('SR-DI-DCCT-01:SIGNAL', datetime.now())
WARNING:root:Assuming timezone for 2019-10-07 16:42:13.301672 is Europe/London
Archive event for PV SR-DI-DCCT-01:SIGNAL: timestamp 2019-10-07
15:42:04.876639 UTC value [301.33007915] severity 0
>>> event.value
array([300.77982715])
>>> event.utc_datetime
datetime.datetime(2019, 10, 7, 16, 2, 54, 928836, tzinfo=<UTC>)

You can also request a range of events, returning an ArchiveData object:

>>> data = jf.get_values('SR-DI-DCCT-01:SIGNAL', utc_datetime(2018, 1, 7), utc_datetime(2018, 1, 8))
>>> data.values
array([[2.51189843e-03],
   [1.56371643e-03],
   [5.54392030e-04],
   ...,
   [2.77373366e+02],
   [2.77329542e+02],
   [2.77287664e+02]])
>>> data.utc_datetimes
array([datetime.datetime(2018, 1, 6, 23, 59, 59, 3897, tzinfo=<UTC>),
   datetime.datetime(2018, 1, 7, 0, 0, 2, 3975, tzinfo=<UTC>),
   datetime.datetime(2018, 1, 7, 0, 0, 5, 4066, tzinfo=<UTC>), ...,
   datetime.datetime(2018, 1, 7, 23, 59, 53, 3885, tzinfo=<UTC>),
   datetime.datetime(2018, 1, 7, 23, 59, 56, 3825, tzinfo=<UTC>),
   datetime.datetime(2018, 1, 7, 23, 59, 59, 3726, tzinfo=<UTC>)],
  dtype=object)
>>> len(data)
28764

Development

aapy uses Pipenv to manage its dependencies.

To install development requirements:

pipenv install --dev

To run the tests and static checks:

pipenv run tests