Python 如何将用户输入解析为数字_Python_Python 3.x

Python 如何将用户输入解析为数字

python python-3.x

Python 如何将用户输入解析为数字,python,python-3.x,Python,Python 3.x,我正在用Python编写一个计算器程序，这是我的教程。这是我的密码： print ("This is a calculator program, press Enter to continue") a = input() while a == "": print("Enter 1 for option 1 which adds") print("Enter 2 for option 2 which subtracts") print("Enter 3 for optio

我正在用Python编写一个计算器程序，这是我的教程。这是我的密码：

print ("This is a calculator program, press Enter to continue")
a = input()

while a == "":
    print("Enter 1 for option 1 which adds")
    print("Enter 2 for option 2 which subtracts")
    print("Enter 3 for option 3 which multiply")
    print("Enter 4 for option 4 which divides")
    print("Enter 5 for option 5 which quits",)

    Option = input("Enter an option number:")
    int(Option)

    if Option == 1:
        Number1 = input("Enter number 1")
        Number2 = input("Enter number 2")
        int(Number1,Number2)
        print(Result = Number1 + Number2)

    if Option == 2:
        Number1 = input("Enter number 1")
        Number2 = input("Enter number 2")
        int(Number1,Number2)
        print(Result = Number1 - Number2)

    if Option == 3:
        Number1 = input("Enter number 1")
        Number2 = input("Enter number 2")
        int(Number1,Number2)
        print(Result = Number1 * Number2)

    if Option == 4:
        Number1 = input("Enter number 1")
        Number2 = input("Enter number 2")
        int(Number1,Number2)
        print(Result = Number1 / Number2)

    if Option == 5:
        break

这是非常基本的，它会打印所有选项编号，然后让我选择一个。所以我输入“1”作为字符串，将其解析为整数1。然而，它并没有直接转到选项1，而是再次循环，这很好，我将在稍后进行排序。但是，当我输入1-5时，它不会进入任何选项。我想我输入了错误的代码来解析它还是什么？

函数的结果是一个

字符串

，您需要使用

int

类型将其转换为

int

>>> foo = "3"
>>> foo
'3'
>>> int(foo)
3

您的误解可能来自python是一种动态类型化语言。但请记住，尽管变量本身是非类型化的，但变量值具有类型

>>> type(foo)
<class 'str'>
>>> type(int(foo))
<class 'int'>

>类型（foo）
>>>类型（int（foo））

您的代码应该更像这样：

print("This is a calculator program. Press Enter to continue.")

while True:
    _ = input()
    print("Enter 1 for option 1 which adds")
    print("Enter 2 for option 2 which subtracts")
    print("Enter 3 for option 3 which multiply")
    print("Enter 4 for option 4 which divides")
    print("Enter 5 for option 5 which quits")

    option = int(input("Enter an option number: "))

    if option == 5:
        break
    else:
        number1 = int(input("Enter number 1: "))
        number2 = int(input("Enter number 2: "))
        if option == 1:
            result = number1 + number2
        elif option == 2:
            result = number1 - number2
        elif option == 3:
            result = number1 * number2
        elif option == 4:
            result = number1 / number2
        print(result)

print ("This is a calculator program, press Enter to continue")
a = input()

while a == "":
    print
    print("Enter 1 for option 1 which adds")
    print("Enter 2 for option 2 which subtracts")
    print("Enter 3 for option 3 which multiply")
    print("Enter 4 for option 4 which divides")
    print("Enter 5 for option 5 which quits",)

    Option = input("Enter an option number:")

    if Option == 1:
        Number1 = int(input("Enter number 1"))
        Number2 = int(input("Enter number 2"))
        result = Number1 + Number2
        print "Result = " + str(result) # To print you have to cast to `str`

    elif Option == 2:
        ...
    elif Option == 3:
        ...
    elif Option == 4:
        ...
    else:
        break

要点：

您没有使用
```
a
```
执行任何操作。所以我去掉了它，调用了
```
input
```
，将其结果存储在
```
\uu
```
中，这是一个变量的标准名称，您不关心它的值
必须将
```
选项
```
显式转换为
```
int
```
。Python不会为您隐式转换，因此
```
'1'！=1
```
您不能就地转换为
```
int
```
——写入
```
int（number1）
```
不起任何作用。您必须编写
```
number1=int（number1）
```
或类似代码
不能在一条
```
int（number1，number2）
```
格式的语句中将多个字符串转换为
```
int
```
。实际上，您在这里所做的是调用
```
int（x，base）
```
，将
```
x
```
转换为
```
int
```
，解释为在base
```
base
```
中
我重构了你的
```
if
```
语句，使之更加简洁
在Python中，变量名通常是小写的
不能在print语句中为变量赋值

发布的代码包含多个错误，下面是更正的代码：

print ("This is a calculator program, press Enter to continue")
a = input()

while a == "":
    print("Enter 1 for option 1 which adds")
    print("Enter 2 for option 2 which subtracts")
    print("Enter 3 for option 3 which multiply")
    print("Enter 4 for option 4 which divides")
    print("Enter 5 for option 5 which quits",)

    Option = int(input("Enter an option number:"))

    if Option == 1:
        Number1 = int(input("Enter number 1"))
        Number2 = int(input("Enter number 2"))
        # int(Number1,Number2)
        Result = Number1 + Number2

    if Option == 2:
        Number1 = int(input("Enter number 1"))
        Number2 = int(input("Enter number 2"))
        # int(Number1,Number2)
        Result = Number1 - Number2

    if Option == 3:
        Number1 = int(input("Enter number 1"))
        Number2 = int(input("Enter number 2"))
        # int(Number1,Number2)
        Result = Number1 * Number2

    if Option == 4:
        Number1 = int(input("Enter number 1"))
        Number2 = int(input("Enter number 2"))
        # int(Number1,Number2)
        Result = Number1 / Number2

    print(Result)

    if Option == 5:
        break

input（）

将输入转换为字符串，因此如果需要读取

int

，则必须强制转换它

在

if

条件下，可以将

input（）

结果（字符串）强制转换为

int

：

Number1 = int(input("Enter number 1"))

然后创建一个变量，比如说

result

，并为其分配数字之和：

result = Number1 + Number2

最后打印结果

print "Result = " + str(result)

最终代码应如下所示：

print("This is a calculator program. Press Enter to continue.")

while True:
    _ = input()
    print("Enter 1 for option 1 which adds")
    print("Enter 2 for option 2 which subtracts")
    print("Enter 3 for option 3 which multiply")
    print("Enter 4 for option 4 which divides")
    print("Enter 5 for option 5 which quits")

    option = int(input("Enter an option number: "))

    if option == 5:
        break
    else:
        number1 = int(input("Enter number 1: "))
        number2 = int(input("Enter number 2: "))
        if option == 1:
            result = number1 + number2
        elif option == 2:
            result = number1 - number2
        elif option == 3:
            result = number1 * number2
        elif option == 4:
            result = number1 / number2
        print(result)

print ("This is a calculator program, press Enter to continue")
a = input()

while a == "":
    print
    print("Enter 1 for option 1 which adds")
    print("Enter 2 for option 2 which subtracts")
    print("Enter 3 for option 3 which multiply")
    print("Enter 4 for option 4 which divides")
    print("Enter 5 for option 5 which quits",)

    Option = input("Enter an option number:")

    if Option == 1:
        Number1 = int(input("Enter number 1"))
        Number2 = int(input("Enter number 2"))
        result = Number1 + Number2
        print "Result = " + str(result) # To print you have to cast to `str`

    elif Option == 2:
        ...
    elif Option == 3:
        ...
    elif Option == 4:
        ...
    else:
        break

注意事项：

您可以使用
```
if else
```
作为结构，因此如果
```
选项==1
```
，则不会检查以下条件
我也会建议你跟随。变量
```
Number1
```
应调用
```
Number1
```
，依此类推

_ = input("This is a calculator program, press Enter to continue")
print ("""Enter 1 for option 1 which adds
          Enter 2 for option 2 which subtracts
          Enter 3 for option 3 which multiplies
          Enter 4 for option 4 which divides
          Enter 5 for option 5 which quits""")
while True:
    Option = input("Enter an option number: ")

    if Option == '1':
        Number1 = int(input("Enter number 1: "))
        Number2 = int(input("Enter number 2: "))
        print("The Result is {0}".format(Number1 + Number2))

    elif Option == '2':
        Number1 = int(input("Enter number 1: "))
        Number2 = int(input("Enter number 2: "))
        print("The Result is {0}".format(Number1 - Number2))

    elif Option == '3':
        Number1 = int(input("Enter number 1: "))
        Number2 = int(input("Enter number 2: "))
        print("The Result is {0}".format(Number1 * Number2))

    elif Option == '4':
        Number1 = int(input("Enter number 1: "))
        Number2 = int(input("Enter number 2: "))
        print("The Result is {0}".format(Number1 / Number2))

    else:
        break

三引号语法适用于长多行字符串
格式化打印字符串的Python方式是方法

you\u var=int（Number1，Number2）

a=input（）

print（Result=Number1+Number2）

print（Number1+Number2）

Number1=int（input（…）

Option=1

str

int

raw\u输入，OP似乎正在使用它。Python3input
的行为类似于Python2raw_input
，并且Python3没有与Python2的input
等价的东西。嘿，你知道你在哪里说过Option=int（input（“输入选项号”）），可以像Option=input（“输入选项号”）/newline int（Option）？@user3216729，是的，但是你需要做Option=int（Option）
啊，对了，泰，我来自C#，所以我会这样做。我倾向于多写一两行，而不是亲自写一行，jsut帮我看一下。谢谢@用户3216729，如果你喜欢这个答案，你可以投票或者接受它C#是目前为止我所知道的唯一一种语言，在C#中，我会这样做：Console.Write（“输入选项号”）/newline string option=Console.ReadLine（）/newline optionnumber=int.Parse（option）。输入（）是否与Console.Write（）/Console.WriteLine（）完全相同？它不让我投票：/嘿，你知道你在哪里说Option=int（输入（“输入选项号”）），可以像这样做吗Option=input（“输入选项号”）/newline int（选项）？我忘了把它放在我的原始帖子里，那是一行代码。