What is positional argument self?

[deanhystad]

Nice! Adding a units enumeration makes this a lot more flexible. To add a new unit all I need to do is add it to the enumeration and provide equations for converting to and from Celsius.

import enum

class Temperature:
    """I am a temperature.  You can specify my units.  I do unit conversion"""
    class Unit(enum.Enum):
        CELSIUS = "C"
        FAHRENHEIT = "F"
        KELVIN = "K"

    # Convert from unit to Celsius
    convert_from = {
        Unit.CELSIUS: lambda x: x,
        Unit.KELVIN: lambda x: x - 273.15,
        Unit.FAHRENHEIT: lambda x: (x - 32) * 5 / 9
    }

    # convert from Celsius to unit
    convert_to = {
        Unit.CELSIUS: lambda x: x,
        Unit.KELVIN: lambda x: x + 273.15,
        Unit.FAHRENHEIT: lambda x: (x * 9) / 5 + 32
    }

    def __init__(self, value=None, unit=Unit.CELSIUS):
        self.units = unit
        self.set(0 if value is None else value)

    def set(self, value, unit=None):
        """Set temperature value.  Can specify unit for value."""
        if unit is None:
            unit = self.units
        self.degreesC = self.convert_from[unit](value)
        return self.degreesC

    def set_units(self, units):
        """Change the default temperature units"""
        self.units = units

    def get(self, unit=None):
        """Get temperature value.  Can specify unit for value."""
        if unit is None:
            unit = self.units
        return self.convert_to[unit](self.degreesC)

    def __str__(self):
        """Get str for printing."""
        return f"{self.get()} °{self.units.value}"

temp = Temperature(273.15, Temperature.Unit.KELVIN)
print("Converting", temp)
for unit in Temperature.Unit:
    temp.set_units(unit)
    print(f"to {unit.name} {temp}")

Output:
Converting 273.15 °K
to CELSIUS 0.0 °C
to FAHRENHEIT 32.0 °F
to KELVIN 273.15 °K