add missing math.py

lib/python/qmk/math.py

@@ -0,0 +1,33 @@
+"""Parse arbitrary math equations in a safe way.
+
+Gratefully copied from https://stackoverflow.com/a/9558001
+"""
+import ast
+import operator as op
+
+# supported operators
+operators = {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.Num): # <number>
+        return node.n
+    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)