A file iteration question/problem

[Arnaud Delobelle]

On Apr 7, 2:09 pm, tinn... at isbd.co.uk wrote:
> Arnaud Delobelle <arno... at googlemail.com> wrote:
> > def recfun(lines):
> >     for line in lines:
> >         # Do stuff
> >         if condition:
> >             recfun(lines)
>
> > lines = iter(open(filename))
> > recfun(lines)
>
> Does that work though?  If you iterate through the file with the "for
> line in lines:" in the first call of recfun(lines) you surely can't do
> "for line in lines:" and get any sort of sensible result in recursive
> calls of recfun(lines) can you?

Try it!  The keyword is iterator.

Here is an example of how this would work, but since you didn't
believe me I changed the context (strings not files) and I didn't make
it as simple as possible ;)

def reclist(string):
    chariter = iter(string + ' ')
    def rec():
        l = []
        word = ''
        for c in chariter:
            if c.isalnum():
                word += c
            elif word and (c.isspace() or c in '[]'):
                l.append(word)
                word = ''
            if c == ']':
                return l
            elif c == '[':
                l.append(rec())
        return l
    return rec()

>>> reclist('40 and 2 eggs but no spam')
['40', 'and', '2', 'eggs', 'but', 'no', 'spam']
>>> reclist('[[40 and 2] eggs] but [no spam]')
[[['40', 'and', '2'], 'eggs'], 'but', ['no', 'spam']]
>>>

--
Arnaud