import re, math

class calculator(object):
	def __init__(self):
		self.error    = None
		self.intRegex = re.compile(r'\b[\d\.]+\b')

	def _return(self, value, error=None):
		if error:
			self.error = error
		return value

	def _safeEval(self, expr, symbols={}):
		return eval(expr, dict(__builtins__=None), symbols)

	def _toFloat(self, match):
		group = match.group()
		if group.find('.') == -1:
			return group + '.0'
		return group

	def calc(self, expr, advanced=False):
		self.error = None
		expr       = expr.replace('^','**')
		expr       = self.intRegex.sub(self._toFloat, expr)
	   	try:
			if advanced:
				return self._return(self._safeEval(expr, vars(math)))
			else:
				return self._return(self._safeEval(expr))
		except Exception, e:
			return self._return(None, error=e)

	def fancyCalc(self, expr, advanced=False):
		result = self.calc(expr, advanced=advanced)
		if not result:
			return "Error [{1}]: `{0}`".format(self.error, self.error.__class__.__name__)
		else:
			return result

calc = calculator()
for equation in ["2+2","test"]:
	print "Result for equation `{0}` is: {1}".format(equation, calc.fancyCalc(equation))