a problem with writing a generator

[Lie Ryan]

On 01/15/10 01:49, Steven D'Aprano wrote:
> On Thu, 14 Jan 2010 15:11:29 +0100, Paweł Banyś wrote:
> 
>> Hello,
>>
>> Please forgive me if I repeat the subject anyhow. I am trying to write a
>> simple program in Python which scans a config file in search for
>> "include" lines. If those lines are found, the files included there are
>> followed and scanned and if any further "include" lines are found, the
>> whole procedure repeats itself. The program ends when the whole tree
>> structure of those "includes" is generated.
>>
>> I seem to have some blackout in my mind because I cannot understand how
>> to use a generator functionality to complete the task. 
> 
> Do you have to use a generator? Just write the code in whatever way feels 
> most comfortable to you. Generators aren't compulsory.
> 
> Anyway, here's an untested recursive generator solution that ignores 
> everything but include lines, and yields the names of the files indented 
> according to the depth of the structure.
> 
> def includes(filename, depth=0):
>     yield "%s%s" % ("  "*depth, filename)
>     f = open(filename, 'r')
>     for line in f:
>         if line.startswith('include '):
>             inc, fname = line.split(None, 1)
>             for line in includes(fname, depth=depth-1):
>                 yield line
>     f.close()

that would always produce an empty file, no?

# another completely untested code; bugs may still be around
def includes(filename, depth=0):
    yield "%s%s" % ("  "*depth, filename)
    f = open(filename, 'r')
    for line in f:
        if line.startswith('include '):
            inc, fname = line.split(None, 1)
            for line in includes(fname, depth=depth+1):
                yield line
        else:
            yield line
    f.close()