如何修复“ ValueError：无法将字符串转换为浮点数”？

debugcn 发表于 Dev

anon_misid

我正在编写一个python代码，用户可以输入尽可能多的数字，直到他们单击Enter而不输入数字。它会进行计算以找到最大值，最小值，平均值和总计。

但是我一直遇到这个错误。

numberList = []

while True:
  enterNumber = input("Please enter a number (RETURN/ENTER when done): ")
  if enterNumber == " ":
    break
  convertFloat = float(enterNumber)
  numberList.append(convertFloat)

theMax = numberList[0]
theMin = numberList[0]
theTotal = 0.0

for value in numberList:
  if value > theMax:
    theMax = value

  if value < theMin:
    themin = value

  theTotal = theTotal + value

average = theTotal / len(numberList)

print("The numbers entered were: ")
for numbers in numberList:
    print(" ", numbers)
print("Max value was: " + str(theMax))
print("Min value was: " + str(theMin))
print("The total is: " + str(theTotal))
print("Average value was: ") + str(avg)

编辑：我修复了它，感谢评论中的人。但是，有一个新错误

Traceback (most recent call last):
  File "main.py", line 31, in <module>
    print("Average value was: ") + str(average)
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

分离器

正如在其他答案中指出的那样，您将输入的字符串与空格而不是空字符串进行比较。但是即使纠正了错误，用户也可以输入错误的格式化数字。这些案例被命名为“异常”，您应该使用try/except构造来处理它。还有一些max，min和sum功能。顺便说一句，您可以使用str.join方法将列表连接到字符串中。

我会建议这样的代码：

numberList = []

while True:
    enterNumber = input("Please enter a number (RETURN/ENTER when done): ")
    print(enterNumber)
    if not enterNumber:
        break
    try:
        convertFloat = float(enterNumber)
        numberList.append(convertFloat)
    except ValueError:
        print("Your entered a wrong formatted number, try one more time.")

theMax = max(numberList)
theMin = min(numberList)
theTotal = sum(numberList)
average = theTotal / len(numberList)

print("The numbers entered were: ")
print(" ".join(map(str, numberList)))
print("Max value was: " + str(theMax))
print("Min value was: " + str(theMin))
print("The total is: " + str(theTotal))
print("Average value was: " + str(average))

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