“返回"在函数中只返回一个值 [英] "Return" in Function only Returning one Value

问题描述

假设我写了一个 for 循环，它将输出 1 到 x 的所有数字:

Let's say I write a for loop that will output all the numbers 1 to x:

x=4
for number in xrange(1,x+1):
    print number,
#Output:
1
2
3
4

现在，将同样的 for 循环放入一个函数中:

Now, putting that same for loop into a function:

def counter(x):
    for number in xrange(1,x+1):
        return number
print counter(4)
#Output:
1

为什么我把for循环放到一个函数里，只能得到一个值?

Why do I only obtain one value when I put the for-loop into a function?

我通过将 for 循环的所有结果附加到一个列表，然后返回该列表来避免这个问题.

I have been evading this problem by appending all the results of the for-loop to a list, and then returning the list.

为什么 for 循环会附加所有结果，而不是一个?:

Why does the for loop append all the results, and not just one?:

def counter(x):
    output=[]
    for number in xrange(1,x+1):
        output.append(number)
    return output

返回所有值的最佳方法是什么，附加到列表似乎非常低效.

What is the best method of returning all the values, appending to a list seems very inefficient.

推荐答案

return 与关键字的名称所暗示的完全一样.当您点击该语句时，它返回并且不会执行该函数的其余部分.

return does exactly like the keyword's name implies. When you hit that statement, it returns and the rest of the function is not executed.

您可能想要的是 yield 关键字.这将创建一个生成器函数(一个返回生成器的函数).生成器是可迭代的.每次执行 yield 表达式时，它们都会产生"一个元素.

What you might want instead is the yield keyword. This will create a generator function (a function that returns a generator). Generators are iterable. They "yield" one element each time the yield expression is executed.

def func():
    for x in range(10):
        yield x

generator = func()
for item in generator:
    print item

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