dcalc.py

#! /usr/bin/env python3

import decimal
import re
import math
import readline


RED = "\033[0;31m"
LIGHT_GREEN = "\033[1;32m"
LIGHT_CYAN = "\033[1;36m"
YELLOW = "\033[1;33m"
END = "\033[0m"
DARK_GRAY = "\033[1;30m"


while True:
    a = input(LIGHT_GREEN + "expr ? " + END)

    if a.strip() == "":
        continue

    try:
        b = a.replace(",", ".")
        b = b.replace("−", "-")
        b = b.replace("×", "*")
        b = b.replace("^", "**")

        v = re.sub(r'(\d+\.?\d*)', r'D("\1")', b)
        w = eval(v, {'D': decimal.Decimal,
                     'sqrt': math.sqrt,
                     'pi': decimal.Decimal(math.pi),
                     'sin': math.sin,
                     'cos': math.cos,
                     'tan': math.tan})
        print("  ⟹  {}{}{} = {}{}{}     {}{}{}".format(YELLOW, a, END, LIGHT_CYAN, w, END, DARK_GRAY, v, END))
    except SyntaxError as e:
        print("  ⟹  {}{}{} : {}".format(RED, a, END, e))
    except NameError as e:
        print("  ⟹  {}{}{} : {}".format(RED, a, END, e))
    except TypeError as e:
        w = eval(b, {'sqrt': math.sqrt,
                     'pi': math.pi,
                     'sin': math.sin,
                     'cos': math.cos,
                     'tan': math.tan})
        print("  ⟹  {}{}{} = {}{}{}     {}{}{}".format(YELLOW, a, END, LIGHT_CYAN, w, END, DARK_GRAY, b, END))
    except Exception as e:
        print("  ⟹  {}{}{} : {}".format(RED, a, END, e))