On Sep 24, 11:23 pm, "Gabriel Genellina" <[EMAIL PROTECTED]> wrote: > En Mon, 24 Sep 2007 23:51:57 -0300, Robert Dailey <[EMAIL PROTECTED]> > escribi?: > > > What I meant was that it's not an option because I'm trying to learn > > regular > > expressions. RE is just as built in as anything else. > > Ok, let's analyze what you want. You have for instance this text: > "<action></action>" > which should become > "<action/>" > > You have to match: > (opening angle bracket)(any word)(closing angle bracket)(opening angle > bracket)(slash)(same word as before)(closing angle bracket) > > This translates rather directly into this regular expression: > > r"<(\w+)></\1>" > > where \w+ means "one or more alphanumeric characters or _", and being > surrounded in () creates a group (group number one), which is > back-referenced as \1 to express "same word as before" > The matched text should be replaced by (opening <)(the word > found)(slash)(closing >), that is: r"<\1/>" > Using the sub function in module re: > > py> import re > py> source = """ > ... <root></root> > ... <root/> > ... <root><frame type="image"><action></action></frame></root> > ... <root><frame type="image"><action/></frame></root> > ... """ > py> print re.sub(r"<(\w+)></\1>", r"<\1/>", source) > > <root/> > <root/> > <root><frame type="image"><action/></frame></root> > <root><frame type="image"><action/></frame></root> > > Now, a more complex example, involving tags with attributes: > <frame type="image"></frame> --> <frame type="image" /> > > You have to match: > (opening angle bracket)(any word)(any sequence of words,spaces,other > symbols,but NOT a closing angle bracket)(closing angle bracket)(opening > angle bracket)(slash)(same word as before)(closing angle bracket) > > r"<(\w+)([^>]*)></\1>" > > [^>] means "anything but a >", the * means "may occur many times, maybe > zero", and it's enclosed in () to create group 2. > > py> source = """ > ... <root></root> > ... <root><frame type="image"></frame></root> > ... """ > py> print re.sub(r"<(\w+)([^>]*)></\1>", r"<\1\2 />", source) > > <root /> > <root><frame type="image" /></root> > > Next step would be to allow whitespace wherever it is legal to appear - > left as an exercise to the reader. Hint: use \s* > > -- > Gabriel Genellina
And let's hope the OP doesn't have to parse anything truly nasty like: <esolang:language name="Python" interpreter_prompt=">>>"></ esolang:language> -- Paul -- http://mail.python.org/mailman/listinfo/python-list
