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am trying to write a regular expression to insert a space in specific location. Am reading html file and trying to insert a space between #WORD<tag so it would be #WORD <

where WORD is a variable, could be anything, as long as its a real word (string)

<p style="text-align: left;" data-redator="true"> #deeds</p><p style="text-align: left;" data-redator="true"></p><p style="text-align: left;" data-redator="true">this is it #$%$%$ dkfj dlkjf dklfj </p>

in the example above, i want to insert a space in #deeds</p> so it would be #deeds </p>

I tried to use string replace and re.sub but i don't know how to replace while maintaining a variable in between..

any advice?

update

I tried the provided in one of the answers and it works well, but problem is that it won't work on unicode characters. I tried to do the following adjustment, it picks up english words but not unicode characters like arabic

re.sub(ur'(#\w+)(<)', ur'\1 \2', c, flags=re.UNICODE)

below is an example of the html

<p style="text-align: left;" data-redator="true"> #$^$%^</p><p style="text-align: left;" data-redator="true"></p><p style="text-align: left;" data-redator="true"> #sdkjf #الكويت</p><p style="text-align: left;" data-redator="true"></p><p style="text-align: left;" data-redator="true"></p>

any suggestions? I used the re.UNICODE flag and tried to use ur before the regular expressions to parse the unicode.. but no luck

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    Show us what you tried, don't just describe it. We can't tell what's wrong with your code if we have to guess what your code is. Commented Jan 19, 2014 at 22:02
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    Meanwhile, trying to parse HTML with regular expressions is usually a bad idea, because HTML is not a regular language. For quick & dirty hacks it can sometimes be useful, but imagine running your code on this page. How would it know the real #deeds from the one inside your example without having the context and structure of the page? Commented Jan 19, 2014 at 22:11

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Since you didn't show us your pattern, I'll make one up, and show you how to make it work, and hopefully that will show you how to make your real pattern work.

So:

r = re.compile(r'#[a-z]+<')

That's a silly pattern, but it will match #deeds<, so it serves as an example. So, how do you insert a space in the right place?

What you need to do is capture it as separate groups:

r = re.compile(r'(#[a-z]+)(<)')

And now, you can use references to those groups:

r.sub(r'\1 \2', s)

(In this case, since your group 2 is a static string, you could simplify it slightly—don't put < in a group, and just use r'\1 <'. But I think it's more readable this way, and certainly more flexible/robust if you later extend what you're doing, and the performance cost is tiny.)

The docs on Regular Expression Syntax show how to create a capturing group, with an optional name, and how to reference it in re.sub; scroll down to the chart 'Context of reference to group "quote"' for details. Also see re.sub.

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There's two proper solutions to what I think your higher-level problem is:

  • Either you're entirely generating the HTML page yourself, in which case you should simply use a templating engine such as Mako (http://www.makotemplates.org/), which will save you tons of trouble further down the line.
  • Or you're trying to alter an HTML page someone else wrote, in which case you want to use a proper HTML parser (such as lxml.html -- http://lxml.de/lxmlhtml.html) because parsing HTML with regular expressions only ever leads to pain and suffering.
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