import re SAFE_EVAL_RE = re.compile(r'^[-+/*()eE0-9.]+$') def safeEval(string): if not SAFE_EVAL_RE.match(string): raise ValueError() return eval(string) def evaluate(value, variables, formulas, MAX_DEPTH=100): tryAgain = True depth = 0 while tryAgain and depth 0: tryAgain = True for x in variables: value,n = re.subn(r'\b' + x + r'\b', repr(variables[x]), value) if n > 0: tryAgain = True depth += 1 if depth >= MAX_DEPTH: raise ValueError() return safeEval(value)