convert.txt

#!/usr/bin/env python3

########################################################
###	           Author: Brennan W. Fieck              ###
###                                                  ###
###       Description -                              ###
###   This script defines a class (`Converter`)      ###
### which is used to convert temperature             ###
### measurements between Celsius, Farenheit, and     ###
### Kelvin.                                          ###
###                                                  ###
###             Notes -                              ###
### * The converter is not aware of "absolute zero," ###
###       and will happily report impossible         ###
###       temperatures when given one as a starting  ###
###       point.                                     ###
### * No type-checking occurs at any point; the      ###
###       converter expects to get a number for a    ###
###       temperature, and two strings as units.     ###
###                                                  ###
### !!!   Both of the above are because I was    !!! ###
### !!! asked to check for "invalid conversions" !!! ###
### !!!   and not invalid inputs. The converter  !!! ###
### !!!  will recognize invalid units, however.  !!! ###
###                                                  ###
### * I assumed that the only use of the converter   ###
###       was to immediately convert from one unit   ###
###       to another "in-place," and so I didn't     ###
###       consider the usefulness of a `Converter`   ###
###       object at any intermediary state during    ###
###       its design.                                ###
###                                                  ###
########################################################


class Converter:
	"""Converts temperatures between Kelvin, Farenheit and Celsius.
	Usage: Converter().convert(temperature, unit).to(other_unit)
	where `temperature` is a `float` and `unit` and `other_unit` are both strings (choose from 'C', 'K' and 'F')."""

	def convert(self, temp, unit):
		if unit == "C":
			self.temps = { 'C': temp, 'K': temp+273.15, 'F': (9.*temp/5.)+32. }
		elif unit == "K":
			self.temps = { 'C': temp-273.15, 'K': temp, 'F': (9.*(temp-273.15)/5.)+32. }
		elif unit == "F":
			self.temps = { 'C': 5.*(temp-32.)/9., 'K': (5.*(temp-32.)/9.)+273.15, 'F': temp }
		else:
			raise Exception("'"+unit+"' is not a valid unit of temperature! Please use 'C', 'K', or 'F'.")
		return self

	def to(self, unit):
		if not self.temps:
			raise Exception("You must convert FROM something to get TO anything else!")
		try:
			return round(self.temps[unit], 2)
		except KeyError as e:
			raise Exception("'"+unit+"' is not a valid unit of temperature! Please use 'C', 'K', or 'F'.")


#When run as the main executable script (e.g. via `python3 /path/to/convert.txt`),
#the following tests are run. Since I wasn't asked to write tests, these were pretty
#much just for me, and so I didn't feel the need to do anything more formal than print
#the outcomes and expected outcomes for some sample conversions.
if __name__ == '__main__':
	print("running tests...")

	#testing conversion from 32F to 0C and 273.15K
	CelsiusResult = Converter().convert(32, "F").to("C")
	KelvinResult = Converter().convert(32, "F").to("K")

	print("F->C: expected 0.00, got "+repr(CelsiusResult))
	print("F->K: expected 273.15, got "+repr(KelvinResult))

	#testing conversion from -100C to 173.15K and -148F
	KelvinResult = Converter().convert(-100, "C").to("K")
	FarenheitResult = Converter().convert(-100, "C").to("F")

	print("C->K: expected 173.15, got "+repr(KelvinResult))
	print("C->F: expected -148.00, got "+repr(FarenheitResult))

	#testing conversion from 270.05K to -3.1C and 26.42F
	CelsiusResult = Converter().convert(270.05, "K").to("C")
	FarenheitResult = Converter().convert(270.05, "K").to("F")

	print("K->C: expected -3.10, got "+repr(CelsiusResult))
	print("K->F: expected 26.42, got "+repr(FarenheitResult))

	#testing invalid conversions
	try:
		Result = Converter().convert(1, "notaunit").to("C")
	except Exception as e:
		print("Conversion from 1'notaunit' to C failed (as expected): "+str(e))
	else:
		print("Conversion from 1'notaunit' to C erroneously succeeded with result: "+str(Result))

	try:
		Result = Converter().convert(1, "C").to("notaunit")
	except Exception as e:
		print("Conversion from 1C to 'notaunit' failed (as expected): "+str(e))
	else:
		print("Conversion from 1C to 'notaunit' erroneously succeeded with result: "+str(Result))