units.py

#!/bin/python3

import re

base = '(\d+\.?\d*)\s*'

units = {
    'kg': {
        'pattern': ['kg', 'kilogram'],
        'convert': 2.20462262185,
        'result': 'lb'
    },
    'g': {
        'pattern': ['g', 'gram'],
        'convert': 0.00220462262,
        'result': 'lb'
    },
    'km': {
        'pattern': ['km', 'kilometer'],
        'convert': 0.621371,
        'result': 'mi'
    },
    'm': {
        'pattern': ['m(?!i)', 'meter'],
        'convert': 3.28083989501,
        'result': 'ft'
    },
    'ft': {
        'pattern': ['ft', 'feet'],
        'convert': 0.3048,
        'result': 'm'
    },
    'yd': {
        'pattern': ['yd', 'yard'],
        'convert': 0.9144,
        'result': 'm'
    },
    'lb': {
        'pattern': ['lb', 'pound'],
        'convert': 0.45359237,
        'result': 'kg'
    },
    'mi': {
        'pattern': ['mile', 'mi'],
        'convert': 1.60934449789,
        'result': 'km'
    },
    'acres': {
        'pattern': ['acre'],
        'convert': 4046.8564224,
        'result': 'km^2'
    },
    'C': {
        'pattern': ['C', 'Celsius'],
        'convert': lambda c: 1.8*c+32,
        'result': '°F'
    },
    'F': {
        'pattern': ['F(?!t)', 'Fahrenheit'],
        'convert': lambda f: (f-32)/1.8,
        'result': '°C'
    }
}

def convert(text):
    messages = []
    for name, unit in units.items():
        pattern = base + '(%s)s?' % '|'.join(unit['pattern'])
        for match in re.finditer(pattern, text, re.I):
            start = match.start()
            value = float(match.groups()[0])
            if callable(unit['convert']):
                res = unit['convert'](value)
            else:
                res = value * unit['convert']
            res = '%.2f' % round(res, 2)
            messages.append((start, '%s %s = %s %s' % (value, name, res, unit['result'])))
    
    messages = sorted(messages, key=lambda m: m[0])
    return '\n'.join([i[1] for i in messages])

print(convert('1kg 1g 1km 1m 1ft 1yd 1lb 1mi 1f 1C 1acre'))