Question

这可能是一个菜鸟问题，但有人可以帮助我吗？我需要确保输入严格是浮点数。无论输入什么类型，我当前的代码都会返回错误。

    pricePerCandy = float(input('Please enter the price per candy (2 decimal places): '))
    if pricePerCandy.isalpha() or pricePerCandy.isalnum():
        print("Please enter the price with 2 decimal places.")
        pricePerCandy = float(input('Please enter the price per candy (2 decimal places): '))

Answer 1

您可以编写一个简单的函数来读取输入，直到用户输入浮点值

>>> def readFloat():
...     while True:
...             try:
...                     value = float(input("Enter value "))
...                     return value
...             except ValueError:
...                     print "Please enter the price with 2 decimal places"

<强>测试

>>> readFloat()
Enter value "asdf"
Please enter the price with 2 decimal places
Enter value "qwer"
Please enter the price with 2 decimal places
Enter value 1.2
1.2

Answer 2

这个怎么样？

import re

x = input('Please enter the price per candy (2 decimal places): ')

while True:
   if not re.match(r"^-?\d+.\d{2}$", x):
       x = input('Please enter the price per candy (2 decimal places): ')
       continue
   else:
      print("OK")
      break

如果您不需要2位小数，则可以将其更改为re.match(r"^-?\d+.\d{1,}$", x)

Answer 3

一旦你确认它可以转换为浮点数，那么请关注它是否有一个小数点，并且在该点之后至少有2个数字出现，类似这样（没有正则表达式）

def read():
while True:
    try:
        value = input("Enter value ")
        value_f = float(value)
        return value
    except ValueError:
        print "Please enter a valid float"


value=str(read())
point_position= value.find('.')
length_ = len(value)

required_decimal_positions = 2

if point_position>-1: 
    if point_position <= length_-(required_decimal_positions+1): # == if only a 2 decimal positions number is valid
        print "Valid"
    else:
        print "No valid - No enough decimals"
else:
    print "No valid - No decimal point"

确保输入是浮点数

3 个答案: