# Unit converter plugin

A plugin for converting measured values from one unit to another unit (a unit converter).

The plugin looks up the symbols (given in the query term) in a list of converters, each converter is one item in the list (compare `ADDITIONAL_UNITS`). If the symbols are ambiguous, the matching units of measurement are evaluated. The weighting in the evaluation results from the sorting of the `list of unit converters`.

Enable in `settings.yml`:

    enabled_plugins:
      ..
      - 'Unit converter plugin'

searx.plugins.unit_converter.symbol_to_si()

  Generates a list of tuples, each tuple is a measure unit and the fields in the tuple are:

  0. Symbol of the measure unit (e.g. ‘mi’ for measure unit ‘miles’ Q253276)

  1. SI name of the measure unit (e.g. Q11573 for SI unit ‘metre’)

  2. Factor to get SI value from measure unit (e.g. 1mi is equal to SI 1m multiplied by 1609.344)

  3. Factor to get measure value from from SI value (e.g. SI 100m is equal to 100mi divided by 1609.344)

  The returned list is sorted, the first items are created from `WIKIDATA_UNITS`, the second group of items is build from `ADDITIONAL_UNITS` and items created from `ALIAS_SYMBOLS`.

  If you search this list for a symbol, then a match with a symbol from Wikidata has the highest weighting (first hit in the list), followed by the symbols from the `ADDITIONAL_UNITS` and the lowest weighting is given to the symbols resulting from the aliases `ALIAS_SYMBOLS`.

searx.plugins.unit_converter.ADDITIONAL_UNITS = [{'from_si': <function <lambda>>, 'si_name': 'Q11579', 'symbol': '°C', 'to_si': <function <lambda>>}, {'from_si': <function <lambda>>, 'si_name': 'Q11579', 'symbol': '°F', 'to_si': <function <lambda>>}]

  Additional items to convert from a measure unit to a SI unit (vice versa).

      {
          "si_name": "Q11579",                 # Wikidata item ID of the SI unit (Kelvin)
          "symbol": "°C",                      # symbol of the measure unit
          "to_si": lambda val: val + 273.15,   # convert measure value (val) to SI unit
          "from_si": lambda val: val - 273.15, # convert SI value (val) measure unit
      },
      {
          "si_name": "Q11573",
          "symbol": "mi",
          "to_si": 1609.344,                   # convert measure value (val) to SI unit
          "from_si": 1 / 1609.344              # convert SI value (val) measure unit
      },

  The values of `to_si` and `from_si` can be of `float` (a multiplier) or a callable (val in / converted value returned).

searx.plugins.unit_converter.ALIAS_SYMBOLS = {'mi': ('L',), '°C': ('C',), '°F': ('F',)}

  Alias symbols for known unit of measure symbols / by example:

      '°C': ('C', ...),  # list of alias symbols for °C (Q69362731)
      '°F': ('F', ...),  # list of alias symbols for °F (Q99490479)
      'mi': ('L',),      # list of alias symbols for mi (Q253276)