From: Tutor <tutor-bounces+sjeik_appie=hotmail....@python.org> on behalf of
Peter Otten <__pete...@web.de>
Sent: Monday, August 27, 2018 6:43 PM
To: tutor@python.org
Subject: Re: [Tutor] need help generating table of contents
Albert-Jan Roskam wrote:
>
> From: Tutor <tutor-bounces+sjeik_appie=hotmail....@python.org> on behalf
> of Peter Otten <__pete...@web.de> Sent: Friday, August 24, 2018 3:55 PM
> To: tutor@python.org
> <snip>
>> The following reshuffle of your code seems to work:
>>
>> print('\r\n** Table of contents\r\n')
>> pattern = '/Title \((.+?)\).+?/Page ([0-9]+)(?:\s+/Count ([0-9]+))?'
>>
>> def process(triples, limit=None, indent=0):
>> for index, (title, page, count) in enumerate(triples, 1):
>> title = indent * 4 * ' ' + title
>> print(title.ljust(79, ".") + page.zfill(2))
>> if count:
>> process(triples, limit=int(count), indent=indent+1)
>> if limit is not None and limit == index:
>> break
>>
>> process(iter(re.findall(pattern, toc, re.DOTALL)))
>
> Hi Peter, Cameron,
>
> Thanks for your replies! The code above indeeed works as intended, but: I
> don't really understand *why*. I would assign a name to the following line
> "if limit is not None and limit == index", what would be the most
> descriptive name? I often use "is_*" names for boolean variables. Would
> "is_deepest_nesting_level" be a good name?
> No, it's not necessarily the deepest level. Every subsection eventually ends
> at this point; so you might call it reached_end_of_current_section
>
> Or just 'limit' ;)
LOL. Ok, now I get it :-)
> The None is only there for the outermost level where no /Count is provided.
> In this case the loop is exhausted.
>
> If you find it is easier to understand you can calculate the outer count aka
> limit as the number of matches - sum of counts:
>
<snip useful info>
>> Also, I don't understand why iter() is required here, and why finditer()
> >is not an alternative.
>finditer() would actually work -- I didn't use it because I wanted to make
> as few changes as possible to your code. What does not work is a list like
>the result of findall(). This is because the inner for loops (i. e. the ones
>in the nested calls of process) are supposed to continue the iteration
>instead of restarting it. A simple example to illustrate the difference:
Ah, the triples cannot be unpacked inside the "for" line of the loop. This
works:
def process(triples, limit=None, indent=0):
for index, triple in enumerate(triples, 1):
title, page, count = triple.groups() # unpack it here
title = indent * 4 * ' ' + title
print(title.ljust(79, ".") + page.zfill(2))
if count:
process(triples, limit=int(count), indent=indent+1)
if limit is not None and limit == index:
break
process(re.finditer(pattern, toc, re.DOTALL))
If I don't do this, I get this error:
File "Q:/toc/toc.py", line 64, in <module>
process(re.finditer(pattern, toc, re.DOTALL))
File "Q:/Ctoc/toc.py", line 56, in process
for index, (title, page, count) in enumerate(triples, 1):
TypeError: '_sre.SRE_Match' object is not iterable
Process finished with exit code 1
Thanks again Peter! Very insightful!
Albert-Jan
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