Appendix

Aggregation types

Aggregation types

Aggregation type	Meaning
avg	The average value in the aggregation period.
avg_ge(val)	The number of days where the average value is greater than or equal to val. Aggregation period must be one day or longer. The argument val is a ValueTuple.
avg_le(val)	The number of days where the average value is less than or equal to val. Aggregation period must be one day or longer. The argument val is a ValueTuple.
count	The number of non-null values in the aggregation period.
diff	The difference between the last and first value in the aggregation period.
exists	Returns True if the observation type exists in the database.
first	The first non-null value in the aggregation period.
firsttime	The time of the first non-null value in the aggregation period.
gustdir	The direction of the max gust in the aggregation period.
has_data	Returns True if the observation type exists in the database and is non-null.
last	The last non-null value in the aggregation period.
lasttime	The time of the last non-null value in the aggregation period.
max	The maximum value in the aggregation period.
maxmin	The maximum daily minimum in the aggregation period. Aggregation period must be one day or longer.
maxmintime	The time of the maximum daily minimum.
maxsum	The maximum daily sum in the aggregation period. Aggregation period must be one day or longer.
maxsumtime	The time of the maximum daily sum.
maxtime	The time of the maximum value.
max_ge(val)	The number of days where the maximum value is greater than or equal to val. Aggregation period must be one day or longer. The argument val is a ValueTuple.
max_le(val)	The number of days where the maximum value is less than or equal to val. Aggregation period must be one day or longer. The argument val is a ValueTuple.
meanmax	The average daily maximum in the aggregation period. Aggregation period must be one day or longer.
meanmin	The average daily minimum in the aggregation period. Aggregation period must be one day or longer.
min	The minimum value in the aggregation period.
minmax	The minimum daily maximum in the aggregation period. Aggregation period must be one day or longer.
minmaxtime	The time of the minimum daily maximum.
minsum	The minimum daily sum in the aggregation period. Aggregation period must be one day or longer.
minsumtime	The time of the minimum daily sum.
mintime	The time of the minimum value.
min_ge(val)	The number of days where the minimum value is greater than or equal to val. Aggregation period must be one day or longer. The argument val is a ValueTuple.
min_le(val)	The number of days where the minimum value is less than or equal to val. Aggregation period must be one day or longer. The argument val is a ValueTuple.
not_null	Returns truthy if any value over the aggregation period is non-null.
rms	The root mean square value in the aggregation period.
sum	The sum of values in the aggregation period.
sum_ge(val)	The number of days where the sum of value is greater than or equal to val. Aggregation period must be one day or longer. The argument val is a ValueTuple.
sum_le(val)	The number of days where the sum of value is less than or equal to val. Aggregation period must be one day or longer. The argument val is a ValueTuple.
tderiv	The time derivative between the last and first value in the aggregation period. This is the difference in value divided by the difference in time.
vecavg	The vector average speed in the aggregation period.
vecdir	The vector averaged direction during the aggregation period.

Units

WeeWX offers three different unit systems:

The standard unit systems used within WeeWX

Name	Encoded value	Note
US	0x01	U.S. Customary
METRICWX	0x11	Metric, with rain related measurements in mm and speeds in m/s
METRIC	0x10	Metric, with rain related measurements in cm and speeds in km/hr

The table below lists all the unit groups, their members, which units are options for the group, and what the defaults are for each standard unit system.

Unit groups, members and options

Group	Members	Unit options	US	METRICWX	METRIC
group_altitude	altitude cloudbase	foot meter	foot	meter	meter
group_amp		amp	amp	amp	amp
group_boolean		boolean	boolean	boolean	boolean
group_concentration	no2 pm1_0 pm2_5 pm10_0	microgram_per_meter_cubed	microgram_per_meter_cubed	microgram_per_meter_cubed	microgram_per_meter_cubed
group_count	leafWet1 leafWet2 lightning_disturber_count lightning_noise_count lightning_strike_count	count	count	count	count
group_data		byte bit	byte	byte	byte
group_db	noise	dB	dB	dB	dB
group_delta_time	daySunshineDur rainDur sunshineDurDoc	second minute hour day	second	second	second
group_degree_day	cooldeg heatdeg growdeg	degree_F_day degree_C_day	degree_F_day	degree_C_day	degree_C_day
group_direction	gustdir vecdir windDir windGustDir	degree_compass	degree_compass	degree_compass	degree_compass
group_distance	windrun lightning_distance	mile km	mile	km	km
group_energy		kilowatt_hour mega_joule watt_hour watt_second	watt_hour	watt_hour	watt_hour
group_energy2		kilowatt_hour watt_hour watt_second	watt_second	watt_second	watt_second
group_fraction	co co2 nh3 o3 pb so2	ppm	ppm	ppm	ppm
group_frequency		hertz	hertz	hertz	hertz
group_illuminance	illuminance	lux	lux	lux	lux
group_interval	interval	minute	minute	minute	minute
group_length		inch cm	inch	cm	cm
group_moisture	soilMoist1 soilMoist2 soilMoist3 soilMoist4	centibar	centibar	centibar	centibar
group_percent	cloudcover extraHumid1 extraHumid2 inHumidity outHumidity pop rxCheckPercent snowMoisture	percent	percent	percent	percent
group_power		kilowatt watt	watt	watt	watt
group_pressure	barometer altimeter pressure	inHg mbar hPa kPa	inHg	mbar	mbar
group_pressurerate	barometerRate altimeterRate pressureRate	inHg_per_hour mbar_per_hour hPa_per_hour kPa_per_hour	inHg_per_hour	mbar_per_hour	mbar_per_hour
group_radiation	maxSolarRad radiation	watt_per_meter_squared	watt_per_meter_squared	watt_per_meter_squared	watt_per_meter_squared
group_rain	rain ET hail snowDepth snowRate	inch cm mm	inch	mm	cm
group_rainrate	rainRate hailRate	inch_per_hour cm_per_hour mm_per_hour	inch_per_hour	mm_per_hour	cm_per_hour
group_speed	wind windGust windSpeed windgustvec windvec	mile_per_hour km_per_hour knot meter_per_second beaufort	mile_per_hour	meter_per_second	km_per_hour
group_speed2	rms vecavg	mile_per_hour2 km_per_hour2 knot2 meter_per_second2	mile_per_hour2	meter_per_second2	km_per_hour2
group_temperature	appTemp dewpoint extraTemp1 extraTemp2 extraTemp3 heatindex heatingTemp humidex inTemp leafTemp1 leafTemp2 outTemp soilTemp1 soilTemp2 soilTemp3 soilTemp4 windchill THSW	degree_C degree_F degree_E degree_K	degree_F	degree_C	degree_C
group_time	dateTime	unix_epoch dublin_jd	unix_epoch	unix_epoch	unix_epoch
group_uv	UV	uv_index	uv_index	uv_index	uv_index
group_volt	consBatteryVoltage heatingVoltage referenceVoltage supplyVoltage	volt	volt	volt	volt
group_volume		cubic_foot gallon liter	gallon	liter	liter
group_NONE	NONE	NONE	NONE	NONE	NONE

Durations

Rather than give a value in seconds, many durations can be expressed using a shorthand notation. For example, in a skin configuration file skin.conf, a value for aggregate_interval can be given as either

aggregate_interval = 3600

or

aggregate_interval = 1h

The same notation can be used in trends. For example:

<p>Barometer trend over the last 2 hours: $trend(time_delta='2h').barometer</p>

Here is a summary of the notation:

Example	Meaning
10800	3 hours
3h	3 hours
1d	1 day
2w	2 weeks
1m	1 month
1y	1 year
hour	Synonym for 1h
day	Synonym for 1d
week	Synonym for 1w
month	Synonym for 1m
year	Synonym for 1y

Class ValueTuple

A value, along with the unit it is in, can be represented by a 3-way tuple called a "value tuple". They are used throughout WeeWX. All WeeWX routines can accept a simple unadorned 3-way tuple as a value tuple, but they return the type ValueTuple. It is useful because its contents can be accessed using named attributes. You can think of it as a unit-aware value, useful for converting to and from other units.

The following attributes, and their index, are present:

Index	Attribute	Meaning
0	value	The data value(s). Can be a series (e.g., [20.2, 23.2, ...]) or a scalar (e.g., 20.2)
1	unit	The unit it is in ("degree_C")
2	group	The unit group ("group_temperature")

It is valid to have a datum value of None.

It is also valid to have a unit type of None (meaning there is no information about the unit the value is in). In this case, you won't be able to convert it to another unit.

Here are some examples:

from weewx.units import ValueTuple

freezing_vt = ValueTuple(0.0, "degree_C", "group_temperature")
body_temperature_vt = ValueTuple(98.6, "degree_F", group_temperature")
station_altitude_vt = ValueTuple(120.0, "meter", "group_altitude")

Class ValueHelper

Class ValueHelper contains all the information necessary to do the proper formatting of a value, including a unit label.

Instance attribute

ValueHelper.value_t

Returns the ValueTuple instance held internally.

Instance methods

ValueHelper.str()

Formats the value as a string, including a unit label, and returns it.

ValueHelper.format(format_string=None, None_string=None, add_label=True, localize=True)

Format the value as a string, using various specified options, and return it. Unless otherwise specified, a label is included.

Its parameters:

• format_string A string to be used for formatting. It must include one, and only one, format specifier.

• None_string In the event of a value of Python None, this string will be substituted. If None, then a default string from skin.conf will be used.

• add_label If truthy, then an appropriate unit label will be attached. Otherwise, no label is attached.

• localize If truthy, then the results will be localized. For example, in some locales, a comma will be used as the decimal specifier.