Help with Tempature Conversion Program

[deanhystad]

I like temperature conversion and I thought it would be fun to write a program in Python. I started with your program, but I didn't like that I had to enter temps in degrees Farenheight and I didn't like having to run the program over each time I wanted to enter a different temperature. I changed the program so the user can enter a temp using any of the units and use a more natural input like this:

Output:
Enter Temperature followed by units: 32 F
0.0 C
150.0 D
32.0 F
273.15 K
0.0 N
491.67 Ra
0.0 Re
7.5 Ro

This was surprisingly easy in Python. For conversion I put all of my equations in a dictionary so I could look them up by unit. I chose Celsius as my standard unit and I have a dictionary of equations to convert from various units to Celsius, and another to convert from Celsius to various units. After that all I had to do was loop, split the input into parts, convert to Celsius, and convert from Celsius to all the other units.

to_celsius = {
    'C'  : lambda C : C,
    'D'  : lambda D : 100 - D * 2 / 3,
    'F'  : lambda F : (F-32)/1.8,
    'K'  : lambda K : K - 273.15,
    'N'  : lambda N : N / 0.33,
    'RA' : lambda RA: (RA - 491.67) / 1.8,
    'RE' : lambda RE: RE * 1.25,
    'RO' : lambda RO: (RO - 7.5) * 40 / 21 }

from_celsius = {
    'C'  : lambda C: C,
    'D'  : lambda C: (100 - C) * 3 / 2,
    'F'  : lambda C: C * 1.8 + 32,
    'K'  : lambda C: C + 273.15,
    'N'  : lambda C: C * 0.33,
    'RA' : lambda C: C * 1.8 + 491.67,
    'RE' : lambda C: C / 1.25,
    'RO' : lambda C: C * 21 / 40 + 7.5 }

units = {'C':'Celsius', 'D':'Delisle', 'F':'Farenhieght', 'K':'Kelvin',
         'N':'Newton', 'Ra': 'Rankine', 'Re':'Reamur', 'Ro':'Romer' }

unit_str = ','.join([f'{sym}:{name}' for sym, name in units.items()])

print("Tempture Conversion\n___________________")

print('Enter temeprature followed by units.  For units use these codes:')
print(unit_str)

while True:
    inp = input('Enter Temperature followed by units: ').split()
    if len(inp) == 0:  ## Nothing entered.  Quit
        break;
    if len(inp) == 1:  ## No units?  Use Celsius as default
        inp.append('C')
    try:
        ## Convert to Celsius
        celsius = to_celsius[inp[1].upper()](float(inp[0]))

        ## Convert Celsius to all units
        for unit in units:
            print(from_celsius[unit.upper()](celsius), unit)

    ## Catch error and offer helpful suggestion
    except ValueError:
        print('Separate temperature and units by space')
    except KeyError:
        print('Use these temperature units\n', unit_str)

It would be pretty easy to convert something like this to one of those programs where you have two boxes for values and two drop-down lists for selecting units.