混淆python - 无法将字符串转换为float [英] Confusing python - Cannot convert string to float

问题描述

我有一个值错误，即使我尝试玩代码，它不起作用。

我如何得到正确的？ - 我使用的是Python 3.3.2！

这里是代码：

如您所见，程序会询问您可以走几英里，并根据您输入的内容给出回应。 p>

这是文本格式的代码：

  print（欢迎来到
 miles = input（你可以走几英里？）
如果float（英里）< = 0：
 print（你以为你是谁？!!现在就走1000英里！）
 elif float（miles）> = 10：
 print（你很健康！保持起来！ 
 elif float（miles）> 0和里程< 
 print（Good，Try doing 10 miles）
 else：
 print（请输入一个数字！）
 miles = float（input你可以走几英里？））
如果里程< = 0：
 print（你认为你是谁？现在去走1000英里！）
 elif miles> = 10：
 print（你很健康！保持起来！）
 elif miles> 0和里程< 10：
打印（好，尝试做10英里）
  

解决方案

这个问题正是Traceback日志所说的：无法将字符串转换为float

• 如果您只有一个字符串，只有数字，python足够聪明地做你想要的，并将字符串转换为一个浮动。


• 如果你有一个字符串使用非数字字符，转换将失败，并提供您所遇到的错误。

大多数人会接近的方式问题是使用 try / except （请参阅这里），或使用 isdigit（）函数（请参阅 here ）。

尝试/除外

  try：
 miles = float（input（你可以走几英里？））
 ex cept：
 print（请输入一个数字！）
  

Isdigit （）

  miles = input（你可以走几英里？）
 if不是miles.isdigit（）：
 print（请输入一个数字！）
  

请注意，如果字符串中有小数点，则后者仍将返回false

编辑

好吧，我将无法再回到你一段时间，所以我会发布答案，以防万一。

  while真的：
 try：
 miles = float（input（你可以走几英里？））
 break 
除了：
 print（请输入一个数字！）
 
＃所有的ifs和东西
  

代码很简单：

• 它将继续尝试将输入转换为浮点数，如果失败，循环回到开始。 li>
  
• 最终成功后，会破坏f循环并转到你放下的代码。

I got a value error and even if I try playing around with the code, it doesn't work!

How can I get it right? - I am using Python 3.3.2!

Here is the code:

As you can see, the program asks for how many miles you can walk and gives you a response depending on what you type in.

This is the code in text format:

print("Welcome to Healthometer, powered by Python...")
miles = input("How many miles can you walk?: ")
if float(miles) <= 0:
    print("Who do you think you are?!! Go and walk 1000 miles now!")
elif float(miles) >= 10:
    print("You are very healthy! Keep it up!")
elif float(miles) > 0 and miles < 10:
    print("Good. Try doing 10 miles")
else:
    print("Please type in a number!")
    miles = float(input("How many miles can you walk?: "))
    if miles <= 0:
        print("Who do you think you are?!! Go and walk 1000 miles now!")
    elif miles >= 10:
        print("You are very healthy! Keep it up!")
    elif miles > 0 and miles < 10:
        print("Good. Try doing 10 miles")

解决方案

The problem is exactly what the Traceback log says: Could not convert string to float

• If you have a string with only numbers, python's smart enough to do what you're trying and converts the string to a float.
• If you have a string with non-numerical characters, the conversion will fail and give you the error that you were having.

The way most people would approach this problem is with a try/except (see here), or using the isdigit() function (see here).

Try/Except

try:
    miles = float(input("How many miles can you walk?: "))
except:
    print("Please type in a number!")

Isdigit()

miles = input("How many miles can you walk?: ")
if not miles.isdigit():
    print("Please type a number!")

Note that the latter will still return false if there are decimal points in the string

EDIT

Okay, I won't be able to get back to you for a while, so I'll post the answer just in case.

while True:
    try:
        miles = float(input("How many miles can you walk?: "))
        break
    except:
        print("Please type in a number!")

#All of the ifs and stuff

The code's really simple:

• It will keep trying to convert the input to a float, looping back to the beginning if it fails.
• When eventually it succeeds, it'll break from the loop and go to the code you put lower down.

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