Python计算器错误输出

Question

所以我使用 python 2.7.8 制作了一个计算器，一切正常，除非有一件事。我想收到错误消息“错误：最小输入：数字操作员号码！”例如，当我尝试计算“2 +”时。但我无法让它工作。如果有人能指出我犯了什么错误，那就太好了。 这是无法正常工作的地方：

except len(self.input) < 3:
        print "ERROR: Minimum Input: Number Operator Number!"

这里是整个代码：

import sys

class Calculator(object):

    def __init__(self, input):
        self.input = input

    def divide(self, number1, number2):
        return number1 / number2

    def add(self, number1, number2):
        return number1 + number2

    def sub(self, number1, number2):
        return number1 - number2

    def mult(self, number1, number2):
        return number1 * number2

    def modulo(self, number1, number2):
        return number1 % number2

    def exponentiate(self, number1, number2):
        return number1 ** number2

    def print_error(self, error):
        print error
        sys.exit(-1)

    def print_result(self, result):
        print result
        sys.exit(0)

    def process_input(self):
        try:
            result = float(self.input[1])
            current_operator = ""
            for element in self.input[2:]:
                if element in ["/", "+", "-", "*", "%", "**"]:
                    current_operator = element
                else:
                    number2 = float(element)
                    if current_operator == "/":
                        result = self.divide(result, number2)
                    elif current_operator == "+":
                        result = self.add(result, number2)
                    elif current_operator == "-":
                        result = self.sub(result, number2)
                    elif current_operator == "*":
                        result = self.mult(result, number2)
                    elif current_operator == "%":
                        result = self.modulo(result, number2)
                    elif current_operator == "**":
                        result = self.exponentiate(result, number2)
                    else:
                        self.print_error(error)

            self.print_result(result)
        except ZeroDivisionError:
            print "ERROR: Caught division by zero!"
        except ValueError:
            print "ERROR: Input number could not be parsed!"
        except OverflowError:
            print "ERROR: Result too large! Overflow encountered."
        except len(self.input) < 3:
            print "ERROR: Minimum Input: Number Operator Number!"

calc = Calculator(sys.argv)
calc.process_input()

感谢您的回答！

Answer 1

如您所见，代码将无法运行。相反，您需要将此部分更改为

if

语句或手动

raise

异常：

旧版本 - 不起作用。

try:
    # ...code...
except len(self.input) < 3:
    print "ERROR: Minimum Input: Number Operator Number!"

新版本 - 选项 A.

if len(self.input) < 3:
    print "ERROR: Minimum Input: Number Operator Number!"
else:
    # ...code...

新版本 - 选项 B.

try:
    if len(self.input) < 3:
        raise RuntimeError("Not enough arguments.")
    # ...code...
except RuntimeError:
    print "ERROR: Minimum Input: Number Operator Number!"

我用

RuntimeError

作为例子，你可能想用更合适的代替。

Answer 2

try:
    assert len(self.input) >= 3
    # ...Your code...
except AssertionError:
    print "ERROR: Minimum Input: Number Operator Number!"

问题是“except”后面必须跟一个异常，而“len(self.input) >= 3”也不例外！ （AssertionError 是个例外）

Answer 3

user_info = input("Enter the following info- Name Age Favorite Sport: ") user_info_split = user_info.split() 打印“你好，” + user_info_split[0] + “！” + “我也喜欢” + user_info_split[2] + “！”