Python-在按下等号之前禁止打印

Question

我有一个基本的计算器脚本，正在尝试让用户按下一个运算符（+，-，*，/或0），然后忽略是否按回车键，而是等到他们按下等号-然后打印结果。我已经安装了键盘模块，并认为我可以只使用“和keyboard.is_pressed”来提示，但这是行不通的。

# You must install keyboard to run this program in order to capture the equal sign key press as a trigger for Enter.
import sys, keyboard

# Create calculate function with cal class.
def calculate():
    class cal():
        def __init__(self,a,b):
            self.a=a
            self.b=b
# Define operations.
        def add(self):
            return self.a+self.b
        def mul(self):
            return self.a*self.b
        def div(self):
            return self.a/self.b
        def sub(self):
            return self.a-self.b
# Prompt for first number.        
    a=int(input("Enter first number: "))
# If first number is zero prompt for rentry.
    while a == 0:
        a=int(input("Enter a first number that is not zero: "))
# If first number isn't 0 then prompt for second number.        
    if a != 0:
        b=int(input("Enter second number: "))
# If second number is zero prompt for rentry.
    while b == 0:
        b=int(input("Enter a second number that is not zero: "))
# If both numbers are != 0 ask for operation.
    obj=cal(a,b)
    operatorChoice = '+'
    if operatorChoice!=0:
        print("Choose operation then press Enter \n + | Add \n - | Subtract \n * | Multiply \n / | Divide \n 0 | Exit")
        operatorChoice = input("Enter operation: ")
# Perform operation based on user selection.
        if operatorChoice == '+' and keyboard.is_pressed('='):
            print("----------\n",a," + ",b," = ",obj.add(),"\n----------")
        elif operatorChoice == '-' and keyboard.is_pressed('='):
            print("----------\n",a," - ",b," = ",obj.sub(),"\n----------")
        elif operatorChoice == '*' and keyboard.is_pressed('='):
            print("----------\n",a," * ",b," = ",obj.mul(),"\n----------")
        elif operatorChoice == '/' and keyboard.is_pressed('='):
            print("----------\n",a," / ",b," = ",round(obj.div(),2),"\n----------")
        elif operatorChoice == '0':
            print("----------\nExit program.\n----------")
# If not one of the provided operations, display error.
        else:
            print("Invalid operation selection.")        
# Add again() function to calculate() function
def again():
    calc_again = input("Do you want to calculate again? Please type Y for YES or N for NO.\n")
    if calc_again.upper() == 'Y':
        calculate()
        again()
    elif calc_again.upper() == 'N':
        print('Okay, bye Felicia!')
    else:
        again()
calculate()
again()