Question

I’m outputting pretty huge XML structure to file and I want user to be able to enable/disable pretty print.

I’m working with approximately 150MB of data,when I tried xml.etree.ElementTree and build tree structure from it’s element objects, it used awfully lot of memory, so I do this manually by storing raw strings and outputing by .write(). My output sequence looks like this:

ofile.write(pretty_print(u'\
\t\t<LexicalEntry id="%s">\n\
\t\t\t<feat att="languageCode" val="cz"/>\n\
\t\t\t<Lemma>\n\
\t\t\t\t<FormRepresentation>\n\
\t\t\t\t\t<feat att="writtenForm" val="%s"/>\n\
\t\t\t\t</FormRepresentation>\n\
\t\t\t</Lemma>\n\
\t\t\t<Sense>%s\n' % (str(lex_id), word['word'], '' if word['pos']=='' else '\n\t\t\t\t<feat att="partOfSpeech" val="%s"/>' % word['pos'])))

inside the .write() I call my function pretty_print which, depending on command line option, SHOULD strip all tab and newline characters

o_parser = OptionParser()
# ....
o_parser.add_option("-p", "--prettyprint", action="store_true", dest="pprint", default=False)
# ....

def pretty_print(string):
    if not options.pprint:
        return string.strip('\n\t')
    return string

I wrote ‘should’, because it does not, in this particular case it does not strip any of the characters.

BUT in this case, it works fine:

for ss in word['synsets']:
    ofile.write(pretty_print(u'\t\t\t\t<Sense synset="%s-synset"/>\n' % ss))

First thing that came on my mind was that there might be some issues with the substitution, but when i print passed string inside the pretty_print function it looks perfectly fine.

Any suggestiones what might cause that .strip() does not work?
Or if there is any better way to do this, I’ll accept any advice

Answer 1

Your issue is that str.strip() only removes from the beginning and end of a string.

You either want str.replace() to remove all instances, or to split it into lines and strip each line, if you want to remove them from the beginning and end of lines.

Also note that for your massive string, Python supports multi-line strings with triple quotes that will make it a lot easier to type out, and the old style string formatting with % has been superseded by str.format() – which you probably want to use instead in new code.