在Python 3.4中按Enter退出While循环

Question

我是Python新手，在过去的几个月里一直在自学。我正在使用的这本书教Python 2.7，而我正试图在3.4中学习Python。现在我已经习惯了同时使用这两种方法，但是对于我的生命，我无法用enter键来确定如何退出while循环。代码显示如下：

total = 0
count = 0
data = eval(input("Enter a number or press enter to quit: "))

while data != "":
    count += 1
    number = data
    total += number
    average = total / count
    data = eval(input("Enter a number or press enter to quit: "))
print("The sum is", total, ". ", "The average is", average)

我一直有这个错误：

Traceback (most recent call last):
  File "/Users/Tay/Documents/Count & Average.py", line 10, in <module>
    data = eval(input("Enter a number or press enter to quit: "))
  File "<string>", line 0

    ^
SyntaxError: unexpected EOF while parsing

我可以在2.7中使用此代码的修改版本，但我想知道如何在3.4中执行此操作。我到处找遍了，似乎找不到答案。

Answer 1

将用户的输入保持为字符串，直到检查其内容：

total = 0
count = 0

while 1:
    data = input("Enter a number or press enter to quit: ")
    try:
        data = float(data)
    except ValueError:
        break
    count += 1
    total += data

average = total / count
print("The sum is " + total ". The average is " + average + ".")

Answer 2

请尝试此正确版本的代码。你的逻辑是正确的，但你有几个错误。您不需要eval，在将数字添加到总数时，您必须将其转换为integer，最后，您必须在打印之前定义函数外部的平均值。

total = 0
count = 0
average = 0
data = input("Enter a number or press enter to quit: ")

while data:
    count += 1
    number = data
    total += int(number)
    average = total / count
    data = input("Enter a number or press enter to quit: ")

print("The sum is {0}. The average is {1}.".format(total, average))

示例：

Enter a number or press enter to quit: 5
Enter a number or press enter to quit: 4
Enter a number or press enter to quit: 3
Enter a number or press enter to quit: 2
Enter a number or press enter to quit: 
The sum is 14. The average is 3.5.

Enter a number or press enter to quit: 
The sum is 0. The average is 0.

Answer 3

我分离了一个eval函数，它是数字，我让它保持浮点数，看起来有点干净。

def isNumber(value):
    try:
        float(value)
        return True
    except ValueError:
        "error"
        return False

total = 0
count = 0
data = input("Enter a number or press enter to quit: ")

while data and isNumber(data):
    count += 1
    number = float(data)
    total += number

average = total / count  #This sentences is more clean here (for me)
data = input("Enter a number or press enter to quit: ")
print("The sum is", total, ". ", "The average is", average)