使用eval进行表达式评估有多安全？

I am building a website where I have a need that user should be able to evaluate some expression based from the value in DB tables, instead of using tools like pyparsing etc, I am thinking of using python itself, and have come up with a solution which is sufficient for my purpose. I am basically using eval to evaluate the expression and passing globals dict with empty I am building a website where I have a need tha