python - CM 到 INCH 转换程序 Python

Question

你好，我正在尝试制作一个转换程序，但我无法让它工作，我将转换多种不同的东西，但我从 CM 开始到 INCH。我收到错误 TypeError: unsupported operand type(s) for/: 'str' and 'float'。这是一些代码:

   print('Press the number of the one you want to convert: ')
   number = input()
   inch = float(2.54)
   if number == '1':
       print('How many inch? ')
       print('There are %s'.format(number / inch))

Here is the whole code:

print('Welcome to the converting program')
print('What of these do you want to convert?')
print(  "\nHow many centimeters in inches? 1"
    "\nHow many milliliters in a pint? 2"
    "\nHow many acres in a square-mile? 3"
    "\nHow many pounds in a metric ton? 4"
    "\nHow many calories in a BTU? 5")

print('Press the number of the one you want to convert: ')

number = float(input()) 

inch = float(2.54)
if number == '1':
    print('How many inch? ')
    print('There are {0}'.format(number / inch))

elif number == '2':
    print('millimeters')

elif number == '3':
    print('acres')

elif number == '4':
    print('pounds')

elif number == '5':
    print('calories') 

Answer 1

%s 是格式化字符串的表示法，%f 应该用于 float 。但是，在较新版本的 Python 中，您应该使用 {0}

print('There are {0}'.format(number / inch))

阅读PEP 3101了解更多相关信息。

此外，正如 Sebastian Hietsch 在他的回答中提到的，您的输入变量是一个字符串，需要首先转换为浮点型。在格式化表达式之前执行此操作。

number = float(input())
inch = float(2.54)

您可能想要添加一些错误处理:

try:
    number = float(input())
except TypeError as e:
    print('input must be a float')
inch = float(2.54)

当然，您需要删除 if 语句中“1”的引号。