RPN Calculator

rpn.py

# TylerJWhit
# RPN Calculator
# 2019.02.21
# Example:
#    python3 rpn.py 3 47 22 + -

import sys

import argparse


def get_argument_parser():
    
    parser = argparse.ArgumentParser('This program is an RPN Calculator')

    parser.add_argument('calc' , nargs = '*', type = str)

    return parser


def parse_arguments():

    parser = get_argument_parser()

    parsed = parser.parse_args(sys.argv[1:])

    return parsed


def process(action, first, second):
    
    print(first, action, second) # Helps user to know the calculation logic

    operands =  {

        '+' : lambda: first + second,

        '-' : lambda: first - second,

        '*' : lambda: first * second,
        
        '/' : lambda: first / second
    }

    run =  operands.get(action, lambda: "Not a valid operand")
    
    return run()



def main():
    
    args = parse_arguments()

    numbers = []
    
    result = None

    for i in args.calc:

        if i.isnumeric():

            numbers.append(int(i))

        else:

            result = process(i, numbers.pop(), numbers.pop())

            # Helps to not carry values to just append. Also how RPN logic works.
            numbers.append(result)

    print(result)


if __name__ == '__main__':