Extracting PI Point Tag about piconnect

[Hugovdberg]

Note that the documentation contains a section API Reference that shows what methods and attributes the different kinds of objects have. The attributes should all have at least some description, if you're missing something please let me know!

I was going to suggest the following, but I noticed the mock API for the tests breaks the automatic detection of the right location:
If you find yourself lost in the API Reference because you don't know in which section a certain object lives, than it might help to navigate there from the tutorials. If you click on the bold class names in the tutorials they link to the exact location in the reference.

Finally, if you know/feel some attribute of an object is stored in the PI Server but it isn't currently available in PIconnect, then please let me know. If it is readily available in the PI AF SDK I can add it pretty quickly usually.

[Hugovdberg]

@jbshiau235 you can install the package from the feature branch using pip install git+https://github.com/Hugovdberg/PIconnect@feature/feature/extract_single_historic_value. Due to the coronacrisis I don't think I'll get around to merging it into the main branch and publishing a new version soon. Both PIPoint and PIAFAttribute have an attribute recorded_time and interpolated_time, that query the data for a single time. The documentation needs work, but hopefully this helps you get started!

[Hugovdberg]

That's an interesting question. Yes, PIPoint , PIAFElement and PIAFAttribute objects all have a name attribute that contains the name of the item. For PIPoint objects this contains the tag name.
So something like this should work, hope that helps:

import re
import PIconnect as PI

pattern = re.compile(r"FQI?[TS]?\d{3}")
with PI.PIServer() as server:
    points = [point 
              for point in server.search("*")
              if pattern.match(point.name)] # or pattern.match(point.tag)

[jbshiau235]

Perfect, that works for me. I was mainly struggling to find documentation regarding what kinds of attributes a PIPoint has that I can extract. Doing "point.tag" works for me as well as "point.current_value" to extract what value it has. I appreciate your help on this!

[jbshiau235]

What attributes can I pull from a PISeries data type? I looked at the API Reference, but it only tells me what parameters to put into a PISeries object. I'm looking to extract recorded values of PIPoint objects into a dictionary or list to put into a table with columns: Tag Name (string), Time Stamp (date/time), Value (either string or number). I can get the tag name from PISeries.tag, and value from PISeries[index] (after guessing around), but I can't seem to get the time stamp to come out. Is there a property I can use to pull that information?

[Hugovdberg]

The PISeries objects itself are not very informative, they are essentially a pandas.Series with very little additional info. They have an attribute PISeries.tag with the tag name, and PISeries.uom with the units of measurement, and the timestamps are used as the PISeries.index but more info is available from the PIPoint objects.

The PIPoint has the following attributes:

• current_value & last_update: latest recorded value and the corresponding time stamp
• name: the tag name
• description: the description of the PI Point
• units_of_measurement: the units of measurement of the values
• raw_attributes: the raw attributes as reported by the PI SDK

But to get a table like you suggest there you could use something like the following snippet:

with PI.PIServer() as server:
    point = server.search("*")[0]
    data = point.recorded_values("-1d", "*")
data.reset_index().rename(columns={"index": "Time Stamp"}).melt(
    id_vars="Time Stamp", var_name="Tag Name", value_name="Value"
)

[jbshiau235]

Additional question regarding data extraction. Is it possible to pull an interpolated value for a PI Tag for a given single point in time? I know the reference shows you how to pull interpolated values over a time range, but I would like to know what the value was at a specific time stamp. I tried doing:

point.interpolated_values(start_time=some_time, end_time=some_time, interval='0s')

However, this didn't work since I believe this function only takes ranges with specified intervals. Ideally something like the current_value attribute would be nice, but for some time in the past history of the data.

[Hugovdberg]

Good question, I've never had the need for that, but I can look into that tomorrow. Op di 10 mrt. 2020 19:02 schreef Jayson Shiau <[email protected]>:

…

Additional question regarding data extraction. Is it possible to pull an interpolated value for a PI Tag for a given single point in time? I know the reference shows you how to pull interpolated values over a time range, but I would like to know what the value was at a specific time stamp. I tried doing: point.interpolated_values(start_time=some_time, end_time=some_time, interval='0s') However, this didn't work since I believe this function only takes ranges with specified intervals. Ideally something like the current_value attribute would be nice, but for some time in the past history of the data. — You are receiving this because you modified the open/close state. Reply to this email directly, view it on GitHub <#506?email_source=notifications&email_token=ABU7VX2V6JQQIKJM66BBYK3RGZ6DXA5CNFSM4KREXWH2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEOMQISI#issuecomment-597230665>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABU7VX5M26J5ZBKPTWWYHELRGZ6DXANCNFSM4KREXWHQ> .

[jbshiau235]

Perfect, thank you very much. Stay healthy!