如何允许用户在计算器中的运算中不输入任何数字

Question

这是我在 Python 中的第三个项目。我正在研究一个计算器，我有所有的操作等，工作得很好。但是，我想让用户不必在两个操作（即欧拉数和 Pi）上输入第二个数字，并且计算器仍然可以工作。例如，如果我现在想将一个数乘以 pi，我需要输入“1”作为第二个数。我想消除这种需要。非常感谢您提供的任何帮助。

import math


def welcome():
    print('''
Welcome to Calculator
''')


# Define our function
welcome()


def calculate():
    operation = input('''
Please type in the math operation you would like to complete:
+ for addition
- for subtraction
* for multiplication
/ for division
** for power
% for modulo
pi to multiply by Pi 
e to multiply by Euler's Number 
''')

    number_1 = float(input('Please enter the first number: '))
    number_2 = float(input('Please enter the second number: '))
    if operation == 'e':
        print('{} * e = '.format(number_1, math.e))
        print(number_1 * math.e)
    elif operation == 'pi':
        print('{} * Pi = '.format(number_1, math.pi))
        print(number_1 * math.pi)
    elif operation == '+':
        print('{} + {} = '.format(number_1, number_2))
        print(number_1 + number_2)
    elif operation == '-':
        print('{} - {} = '.format(number_1, number_2))
        print(number_1 - number_2)
    elif operation == '*':
        print('{} * {} = '.format(number_1, number_2))
        print(number_1 * number_2)
    elif operation == '/':
        print('{} / {} = '.format(number_1, number_2))
        print(number_1 / number_2)
    elif operation == '**':
        print('{} ** {} ='.format(number_1, number_2))
        print(number_1 ** number_2)
    elif operation == '%':
        print('{} % {} ='.format(number_1, number_2))
        print(number_1 % number_2)
    else:
        print('You have not typed a invalid operator, please run the program again.')

    # Add again() function to calculate() function
    again()


def again():
    calc_again = input('''
Do you want to calculate again?
Please type Y for YES or N for NO.
''')

    if calc_again.upper() == 'Y':
        calculate()
    elif calc_again.upper() == 'N':
        print("Thank you for using the calculator. I'll be here whenever you need me.")
    else:
        again()


# Call calculate() outside of the function
calculate()

Answer 1

在上面加一个if条件就可以了

number_2 = float(input('Please enter the second number: '))

像这样

if(operation != 'e' || operation != 'pi'):
   number_2 = float(input('Please enter the second number: '))

Answer 2

着眼于您需要更改的特定片段，这是一种方法：

...
    number_1 = float(input('Please enter a number: '))
    if operation == 'e' or operation == 'pi':
        if operation == 'e':
            print('{} * e = '.format(number_1, math.e))
            print(number_1 * math.e)
        elif operation == 'pi':
            print('{} * Pi = '.format(number_1, math.pi))
            print(number_1 * math.pi)
    else:
        number_2 = float(input('Please enter a second number: '))
        if operation == '+':
            print('{} + {} = '.format(number_1, number_2))
            print(number_1 + number_2)
        elif operation == '-':
            print('{} - {} = '.format(number_1, number_2))
            print(number_1 - number_2)
...

Answer 3

在对 e 和 pi 进行条件检查后，将第二个数字的输入移动到所有循环中，即可解决此问题，而无需对代码进行太多更改。

举个例子：

    number_1 = float(input('Please enter the first number: '))
    if operation == 'e':
        print('{} * e = '.format(number_1, math.e))
        print(number_1 * math.e)
    elif operation == 'pi':
        print('{} * Pi = '.format(number_1, math.pi))
        print(number_1 * math.pi)
    elif operation == '+':
        number_2 = float(input('Please enter the second number: '))
        print('{} + {} = '.format(number_1, number_2))
        print(number_1 + number_2)

这不符合最佳做法，但它应该按照您的意愿完成。如果您想要比这更好的方法，我可以编辑此答案以包括改进及其更好的原因。

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