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982 B · 33 lines
Python
at master
12345678910111213141516171819202122232425262728293031323334"""Parse arbitrary math equations in a safe way.
Gratefully copied from https://stackoverflow.com/a/9558001"""import astimport operator as op
# supported operatorsoperators = {ast.Add: op.add, ast.Sub: op.sub, ast.Mult: op.mul, ast.Div: op.truediv, ast.Pow: op.pow, ast.BitXor: op.xor, ast.USub: op.neg}
def compute(expr): """Parse a mathematical expression and return the answer.
>>> compute('2^6') 4 >>> compute('2**6') 64 >>> compute('1 + 2*3**(4^5) / (6 + -7)') -5.0 """ return _eval(ast.parse(expr, mode='eval').body)
def _eval(node): if isinstance(node, ast.Constant): # <number> return node.value elif isinstance(node, ast.BinOp): # <left> <operator> <right> return operators[type(node.op)](_eval(node.left), _eval(node.right)) elif isinstance(node, ast.UnaryOp): # <operator> <operand> e.g., -1 return operators[type(node.op)](_eval(node.operand)) else: raise TypeError(node)