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From: Peter Otten <__peter__@web.de>
Newsgroups: comp.lang.python
Subject: Re: delete from pattern to pattern if it contains match
Date: Fri, 22 Apr 2016 11:24:06 +0200
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harirammanohar@gmail.com wrote:

> On Thursday, April 21, 2016 at 7:03:00 PM UTC+5:30, Jussi Piitulainen
> wrote:
>> harirammanohar@gmail.com writes:
>> 
>> > On Monday, April 18, 2016 at 12:38:03 PM UTC+5:30,
>> > hariram...@gmail.com wrote:
>> >> HI All,
>> >> 
>> >> can you help me out in doing below.
>> >> 
>> >> file:
>> >> <start>
>> >>  guava
>> >> fruit
>> >> <end>
>> >> <start>
>> >>  mango
>> >> fruit
>> >> <end>
>> >> <start>
>> >>  orange
>> >> fruit
>> >> <end>
>> >> 
>> >> need to delete from start to end if it contains mango in a file...
>> >> 
>> >> output should be:
>> >> 
>> >> <start>
>> >>  guava
>> >> fruit
>> >> <end>
>> >> <start>
>> >>  orange
>> >> fruit
>> >> <end>
>> >> 
>> >> Thank you
>> >
>> > any one can guide me ? why xml tree parsing is not working if i have
>> > root.tag and root.attrib as mentioned in earlier post...
>> 
>> Assuming the real consists of lines between a start marker and end
>> marker, a winning plan is to collect a group of lines, deal with it, and
>> move on.
>> 
>> The following code implements something close to the plan. You need to
>> adapt it a bit to have your own source of lines and to restore the end
>> marker in the output and to account for your real use case and for
>> differences in taste and judgment. - The plan is as described above, but
>> there are many ways to implement it.
>> 
>> from io import StringIO
>> 
>> text = '''\
>> <start>
>>   guava
>> fruit
>> <end>
>> <start>
>>   mango
>> fruit
>> <end>
>> <start>
>>   orange
>> fruit
>> <end>
>> '''
>> 
>> def records(source):
>>     current = []
>>     for line in source:
>>         if line.startswith('<end>'):
>>             yield current
>>             current = []
>>         else:
>>             current.append(line)
>> 
>> def hasmango(record):
>>     return any('mango' in it for it in record)
>> 
>> for record in records(StringIO(text)):
>>     hasmango(record) or print(*record)
> 
> Hi,
> 
> not working....this is the output i am getting...
> 
> \

This means that the line

>> text = '''\

has trailing whitespace in your copy of the script.

>  <start>
>    guava
>  fruit
> 
> <start>
>    orange
>  fruit

Jussi forgot to add the "<end>..." line to the group. To fix this change the 
generator to

def records(source):
    current = []
    for line in source:
        current.append(line)
        if line.startswith('<end>'):
            yield current
            current = []


>>     hasmango(record) or print(*record)

The

print(*record)

inserts spaces between record entries (i. e. at the beginning of all lines 
except the first) and adds a trailing newline. You can avoid this by 
specifying the delimiters explicitly:

if not hasmango(record):
    print(*record, sep="", end="")

Even with these changes code still looks somewhat brittle...