使用生成器表达式有什么问题? [英] What's wrong with my use of generator expression?

问题描述

我有以下代码，其中我尝试将范围的字符串表示形式转换为数字列表.例如，如果输入为'0-0,3-5,7-10'，则预期输出为[0,3,4,5,7,8,9,10].但是，我在以下位置出现了错误:

I have the following code, in which I try to convert a string representation of ranges to a list of numbers. For example, if the input is '0-0,3-5,7-10' the expected output is [0,3,4,5,7,8,9,10]. However, I got an error at:

for l,h in r.split('-') 

表示没有足够的值可解压.我的理由是，r的格式应为'x-y'，因此，如果将其除以'-'，则应该返回两个值.怎么了?

which it says not enough values to unpack. My reasoning is that, r should have the form 'x-y', so if I split it by '-', I should get two values back. What's wrong with that?

def parse_ranges(ranges):
    """Return a list of numbers corresponding to number ranges in a string"""
    g = (
        (l,h)
        for r in ranges.split(',')
        for l,h in r.split('-')
        )
    return (x
            for range_tuple in g
            for l,h in range_tuple
            for x in range(int(l), int(h)+1)
            )

parse_ranges('0-5,8-10,11-13')

推荐答案

您的循环太多了.由于您试图将两个数字保持在一起，因此不需要第二个嵌套循环.第二个是将结果展平:

You've got a loop too many. Since you're trying to keep the two numbers together you don't need a second nested loop. The second one is flattening the results:

>>> [x for r in s.split(',') for x in r.split('-')]
['0', '0', '3', '5', '7', '10']

使用一个使数字保持配对:

Use one to keep the numbers paired:

>>> [r.split('-') for r in s.split(',')]
[['0', '0'], ['3', '5'], ['7', '10']]

然后，通过第二个理解，可以通过将l和h拆包就位来组合前两个for循环.

Then with the second comprehension you can combine the first two for loops by unpacking l and h in place.

return (x
        for l,h in g
        for x in range(int(l), int(h)+1)
        )

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