python-testing-101/calculator.py at master · python-frederick/python-testing-101 · GitHub

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import numbers

class CalculatorError(Exception):

"""For calculator errors"""

class Calculator:

"""A terrible calculator."""

def add(self, a, b):

"""Add two numbers."""

self._check_operand(a)

self._check_operand(b)

return a + b

def subtract(self, a, b):

"""Subtract two numbers."""

return a - b

def multiply(self, a, b):

"""Multiply two numbers."""

return a * b

def divide(self, a, b):

"""Divide two numbers."""

try:

return a / b

except ZeroDivisionError as ex:

raise CalculatorError("You can't divide by zero.") from ex

def _check_operand(self, operand):

"""Check that the operand is a number."""

if not isinstance(operand, numbers.Number):

raise CalculatorError(f'"{operand}" is not a number.')

if __name__ == "__main__":

print("Let's calculate!")

print("Press Ctrl+C to quit.")

calculator = Calculator()

operations = {

"1": calculator.add,

"2": calculator.subtract,

"3": calculator.multiply,

"4": calculator.divide,

}

while True:

print("Pick a calculation:")

for choice, operation in sorted(operations.items()):

print(f"{choice}: {operation.__name__}")

operation = input("What operation? ")

if operation not in operations:

print("Sorry, that's not a valid choice.")

continue

a = float(input("Select first operand: "))

b = float(input("Select second operand: "))

try:

print("The result is: {}\n".format(operations[operation](a, b)))

except CalculatorError as error:

print(error)

python-testing-101/calculator.py at master · python-frederick/python-testing-101 · GitHub

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