Tiny calculator as a Search Action for XFCE whisker menu search box

whisker-calculator.py

#!/usr/bin/env python3

"""
A tiny calculator for the XFCE whisker menu search box
"Install" by right-clicking the XFCE top-left ("whisker") menu
  and saying Properties. Then, in "Search Actions", add a new
  Search Action with Name: calculator, Pattern: ^[0-9+/* -]+$
  Command: python path/to/this/file/whisker-calculator.py
  and tick "Regular expression".
You should now be able to type "2 + 3+4" into the search box
  and get the answer in a notification.
"""

import sys, json, time
import ast
import operator
import gi
gi.require_version('Notify', '0.7')
from gi.repository import GObject
from gi.repository import Notify

def calc(expr: str):
    return compute(ast.parse(expr, mode="eval").body)


# calculator from https://github.com/theRealProHacker/MathEvaluator
op_map = {
    # binary
    ast.Add: operator.__add__,
    ast.Sub: operator.__sub__,
    ast.Div: operator.__truediv__,
    ast.Mult: operator.__mul__,
    # unary
    ast.UAdd: operator.__pos__,
    ast.USub: operator.__neg__,
}

allowed_types = {int, float}


def compute(expr):
    match expr:
        case ast.Constant(value=value):
            if type(value) not in allowed_types:
                raise SyntaxError(
                    f"Not a number {value!r}"
                )
            return value
        case ast.UnaryOp(op=op, operand=value):
            try:
                return op_map[type(op)](compute(value))  # type: ignore
            except KeyError:
                raise SyntaxError(f"Unknown operation {ast.unparse(expr)}")
        case ast.BinOp(op=op, left=left, right=right):
            try:
                return op_map[type(op)](compute(left), compute(right))  # type: ignore
            except KeyError:
                raise SyntaxError(f"Unknown operation {ast.unparse(expr)}")
        case x:
            raise SyntaxError(f"Invalid Node {ast.dump(x)}")

class NotifyClass(GObject.Object):
    def __init__(self):

        super(NotifyClass, self).__init__()
        # lets initialise with the application name
        Notify.init("whisker-calculator")

    def send_notification(self, title, text, file_path_to_icon=""):

        n = Notify.Notification.new(title, text, file_path_to_icon)
        n.set_timeout(5000)
        n.show()

equation = " ".join(sys.argv[1:])
my = NotifyClass()
my.send_notification(f"Result of {equation}", f"{calc(equation)}",
    "/usr/share/icons/Humanity/apps/48/gnome-calculator.svg")