如何制作一個 python 計算器，它可以對兩個以上的數字進行加、減、乘、除、冪和取模

Question

我是 Python 的新手，我想知道如何制作一個可以對兩個以上數字進行加、減、乘、除和其他運算符的計算器。 如果您能給我一個解釋，我將不勝感激。 我之所以質疑，是因為我認為這是一種糟糕且低效的方法，即為更多運算符和更多數字添加更多 elif 標簽

TL：DR（我猜）：我想過用 python 制作一個計算器，它有更多運算符和數字的選項（但我不知道如何制作一個更簡單的計算器：即：30 + 30 * 30. 67.874 / 20 . 69 + 69 + 69 + 69 + 69 + 69. 30 ** （我認為這是一個冪運算符） 2. 等等 如果你不明白我想要什么，我可以幫助你，你可以問我

Answer 1

這是我的普通計算器，沒有輸入兩個以上的數字和一個運算符

def add(x, y):
return x + y


def subtract(x, y):
return x - y


def multiply(x, y):
return x * y


def divide(x, y):
return x / y


num1 = float(input("Enter a number :"))
op = input("Enter your selected operator :")
num2 = float(input("Enter another number :"))

if op == "+":
print(num1, "+", num2, "=", add(num1, num2))

elif op == "-":
print(num1, "-", num2, "=", subtract(num1, num2))

elif op == "*":
print(num1, "*", num2, "=", multiply(num1, num2))

elif op == "/":
print(num1, "/", num2, "=", divide(num1, num2))

else:
print("Invalid input")

我知道這個評論/答案代碼沒有縮進，但是堆棧不會讓我用縮進發布，而且文件本身確實有縮進，所以 idk

Answer 2

result = None
operand = None
operator = None
wait_for_number = True

while True:
    if operator == '=':
        print(f"Result: {result}")
        break
    elif wait_for_number == True:
        while True:
            try:
                operand = float(input("Enter number: "))
            except ValueError:
                print("Oops! It is not a number. Try again.")
            else:
                if result == None:
                    result = operand
                else:
                    if operator == '+':
                        result = result + operand
                    elif operator == '-':
                        result = result - operand
                    elif operator == '*':
                        result = result * operand
                    elif operator == '/':
                        result = result / operand
                break
        wait_for_number = False
    else:
        while True:
            operator = input("Enter one of operators +, -, *, /, =: ")
            if operator in ('+', '-', '*', '/', '='):
                break
            else:
                print("Oops! It is not a valid operator. Try again.")
        wait_for_number = True

Answer 3

你的問題不夠清楚，但如果我做對了，這應該可行。 需要注意的重要一點：使用 eval() function 不是一個好習慣，因為如果輸入不是來自您，它可能非常危險。 以下是它的一些危險： https://nedbatchelder.com/blog/201206/eval_really_is_dangerous.html

編碼：

# the function takes an operator as a string like: “*” and multiple numbers thanks to the * (args) operator.
def calculate(operator, *numbers):
    
    result = numbers[0]

    #the for cycle goes through all numbers except the first
    for number in range(1, len(numbers)):
        #the eval() function makes it possible to python to interpret strings as a code part
        result = eval(f"{result} {operator} {str(numbers[i])}")
    print(result)

這是沒有 eval() 的代碼。

import operator

# the function takes an operator as a string like: “*” and multiple numbers thanks to the * (args) operator.
def calculate(op, *numbers):

   # binding each operator to its string counterpart
   operators = {
       "+": operator.add,
       "-": operator.sub,
       "*": operator.mul,
       "/": operator.truediv
   }

   result = numbers[0]

   #the for cycle goes through all numbers except the first
   for number in range(1, len(numbers)):
       # carrying out the operation, using the dictionary above
       result = operators[op](result, numbers[number])
   print(result)