令人困惑的python - 无法将字符串转换为浮点数 [英] Confusing python - Cannot convert string to float

问题描述

我收到了一个值错误，即使我尝试玩弄代码，它也不起作用！

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

我怎样才能做到正确?- 我使用的是 Python 3.3.2！

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

这是代码:

如您所见，该程序会询问您可以步行多少英里，并根据您输入的内容给出响应.

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.

这是文本格式的代码:

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")

推荐答案

问题正是 Traceback 日志所说的:Could not convert string to float

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

• 如果您有一个只有数字的字符串，python 足够聪明，可以执行您正在尝试的操作并将字符串转换为浮点数.
• 如果您有一个包含非数字字符的字符串，转换将失败并出现您遇到的错误.

大多数人解决这个问题的方法是使用 try/except(参见 此处)，或使用 isdigit() 函数(参见 这里).

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

尝试/排除

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!")

注意，如果字符串中有小数点，后者仍然会返回false

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

好的，我有一段时间不能回复你，所以我会发布答案以防万一.

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

代码非常简单:

• 它将继续尝试将输入转换为浮点数，如果失败则循环回到开头.
• 当它最终成功时，它会跳出循环并转到您放低的代码.

这篇关于令人困惑的python - 无法将字符串转换为浮点数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！