Station fields

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Any $station report tag can be listed as a field (6.3), written with the $ removed. The values are evaluated against the exact object behind the report tag (weewx.station.Station), so they render as the report would render them.

Examples:

station.uptime.raw                WeeWX uptime in seconds
station.uptime.long_form()        e.g., 25 days, 21 hours, 15 minutes
station.os_uptime.raw             server uptime in seconds
station.os_uptime.long_form()
station.version                   the WeeWX version, e.g., 5.4.0
station.python_version
station.hardware                  e.g., Vantage
station.location                  [Station] location from weewx.conf
station.altitude                  e.g., 700 feet
station.altitude.meter.raw        unit conversions work as in report tags
station.latitude                  ["37", "24.00", "N"] — the same (degrees,
                                  minutes, hemisphere) parts the report tag
                                  exposes, as a json array

Those are examples, not the whole set. $station is WeeWX’s own Station object, so anything it exposes can be a field. In current WeeWX that is uptime, os_uptime, version, python_version, altitude, latitude, longitude, rain_year_str, and — reached through the station info it carries — hardware, location, station_url, webpath, week_start, rain_year_start, altitude_vt, latitude_f and longitude_f. If a $station tag works in a Cheetah template, it works here.

One of them carries a month name: rain_year_str, the abbreviated month the rain year starts in. Which language that is written in comes from the report’s locale, not from its lang file — a German report shows Okt — and, as everywhere else, lang has to be a locale name the machine knows before any of that happens. See Month names and decimal points. (Before 7.4 it took whatever locale weewxd itself started under, whichever report asked for it.)

The point: a restart-correct live uptime

The point of station fields is uptime and os_uptime: they are recomputed on every loop packet, so a live uptime readout is correct within a packet or two of a weewxd or server restart.

The report-cycle alternative — shipping $station.uptime.raw in a template and extrapolating in javascript — is wrong after every restart: it shows the pre-restart uptime still climbing until the next report cycle runs.

Every other $station attribute is constant for the life of the weewxd process; loopdata computes those once and repeats the value in every write, so a page that is not itself a WeeWX report can still show them.

Notes

Station fields are current-only: no period prefix, no aggregate.
round(n) and the format specs/calls work as on observation and almanac fields: .raw on uptime/os_uptime/altitude (ValueHelpers), identity on plain values (station.week_start.raw); .formatted, format(...), nolabel(...), string(...), long_form(...) on the ValueHelpers only.
Unit conversions chain as in report tags: station.altitude.meter.raw.
A $station attribute whose value is a tuple of scalars (e.g. station.latitude’s degrees/minutes/hemisphere) is emitted as a json array.
The json key is the field entry verbatim, so element ids can match keys as usual.