如何在python中从字符串中提取数学方程

Question

我有一个数学方程和字符串的问题。如果用户给出一个字符串格式的数学方程，我该如何从字符串中得到它并计算值？

Input: 
x = 1
y = 2
formula = "x+y"
Output:
formula = x+y
formula = 3

Answer 1

>>> x, y = 1, 2
>>> formula = "x+y"
>>> print('formula = ' + formula)
formula = x+y
>>> print('formula = ' + str(eval(formula)))
formula = 3