Simple Calculator with Functionality to Use Previous Answer

PyCalculator.py

'''
This class is designed to be used for mathematical
calculations only.

This program has the functionality to remember the
previous answer which you needed to calculate.
This code was orginally proposed in this issue,
link below - 

https://github.com/AceLewis/my_first_calculator.py/issues/24

This program is deviated from Calculator.py. The link
for that is below - 

https://gist.github.com/rudrathegreat/de0f463c7304af152cccd34ce0cd5a61

NumPy is a Python module programmed in Python, C 
and FORTAN designed to do fast calculations in
Python. This is because Python is a very slow
program and when using the default operations
in Python, it often doen't give you the coreect
answer and it takes a long time to do so.

The math module is really good for many operations
found in a scientific calculator. It includes log,
sqrt, powers, etc.

More functionality coming soon!
'''

import math 
import numpy as np

class Calculator(object):

    def __init__(self):
        self.answer = 0

    def add(self, num1, num2):
        try:
            if str(num1) == 'Ans':
                answer = np.int(self.answer) + num2
            else:
                answer = np.int(num1) + np.int(num2)
            self.answer = answer
            return answer
        except Exception as e:
            print('Error Calculating: {}'.format{e})
            
    def subtract(self, num1, num2):
        try:
            if str(num1) == 'Ans':
                answer = np.int(self.answer) - num2
            else:
                answer = np.int(num1) - np.int(num2)
            self.answer = answer
            return answer
        except Exception as e:
            print('Error Calculating: {}'.format{e})

    def multiply(self, num1, num2):
        try:
            if str(num1) == 'Ans':
                answer = np.int(self.answer) * num2
            else:
                answer = np.int(num1) + np.int(num2)
            self.answer = answer
            return answer
        except Exception as e:
            print('Error Calculating: {}'.format{e})

    def divide(self, num1, num2):
        try:
            if str(num1) == 'Ans':
                answer = np.int(self.answer) / num2
            else:
                answer = np.int(num1) / np.int(num2)
            self.answer = answer
            return answer
        except Exception as e:
            print('Error Calculating: {}'.format{e})