keyboard stuff
auri.ee
1"""Parse arbitrary math equations in a safe way.
2
3Gratefully copied from https://stackoverflow.com/a/9558001
4"""
5import ast
6import operator as op
7
8# supported operators
9operators = {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}
10
11
12def compute(expr):
13 """Parse a mathematical expression and return the answer.
14
15 >>> compute('2^6')
16 4
17 >>> compute('2**6')
18 64
19 >>> compute('1 + 2*3**(4^5) / (6 + -7)')
20 -5.0
21 """
22 return _eval(ast.parse(expr, mode='eval').body)
23
24
25def _eval(node):
26 if isinstance(node, ast.Constant): # <number>
27 return node.value
28 elif isinstance(node, ast.BinOp): # <left> <operator> <right>
29 return operators[type(node.op)](_eval(node.left), _eval(node.right))
30 elif isinstance(node, ast.UnaryOp): # <operator> <operand> e.g., -1
31 return operators[type(node.op)](_eval(node.operand))
32 else:
33 raise TypeError(node)