在Python 3.4中按回车退出While循环

Question

我是 Python 的新手，过去几个月一直在自学。我正在使用的书教 Python 2.7，而我正在尝试学习 Python 3.4。我现在已经习惯了同时使用这两种方法，但是对于我的一生，我无法弄清楚如何使用回车键退出这个 while 循环。代码如下所示：

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)

我不断收到此错误：

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

我可以获得此代码的修改版本以在 2.7 中运行，但我想知道如何在 3.4 中执行此操作。我到处搜索，似乎找不到答案。

Answer 1

试试这个更正后的代码版本。你的逻辑是正确的，但你有一些错误。您不需要 eval，在将其添加到总数时必须将数字转换为 integer，最后您必须在打印出来之前在函数外部定义平均值。

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))

例子:

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 2

将用户的输入保存为字符串，直到您检查其内容：

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 3

我分离了一个 eval 函数 isNumber 我让它保持浮动小数，它看起来更干净一些。

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)

在Python 3.4中按回车退出While循环

Press Enter to exit While Loop in Python 3.4

python

exit-code

while-loop

python-3.x