Re: NEWB: reverse traversal of xml file

manstey wrote:
Hi,

I have an xml file of about 140Mb like this:

<book>
<record>
...
<wordpartWTS>1</wordpartWTS>
</record>
<record>
...
<wordpartWTS>2</wordpartWTS>
</record>
<record>
...
<wordpartWTS>1</wordpartWTS>
</record>
</book>

I want to traverse it from bottom to top and add another field to each
record <totalWordPart>1</totalWordPart>
which would give the highest value of wordpartWTS for each record for
each word

so if wordparts for the first ten records were 1 2 1 1 1 2 3 4 1 2
I want totalWordPart to be 2 2 1 1 4 4 4 4 2 2

I figure the easiest way to do this is to go thru the file backwards.

Any ideas how to do this with an xml data file?

You need to iterate from the beginning and use itertools.groupby:

from itertools import groupby

def enumerate_words(parts):
word_num = 0
prev = 0
for part in parts:
if prev >= part:
word_num += 1
prev = part
yield word_num, part


def get_word_num(item):
return item[0]

parts = 1,2,1,1,1,2,3,4,1,2
for word_num, word in groupby(enumerate_words(parts), get_word_num):
parts_list = list(word)
max_part = parts_list[-1][1]
for word_num, part_num in parts_list:
print max_part, part_num

prints:

2 1
2 2
1 1
1 1
4 1
4 2
4 3
4 4
2 1
2 2

.

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