Translate github flavored markdown regex from ruby to python

Question

I'm trying to get an implementation of github flavored markdown working in python, with no luck... I don't have much in the way of regex skills.

Here's the ruby code from github:

# in very clear cases, let newlines become <br /> tags
text.gsub!(/(\A|^$\n)(^\w[^\n]*\n)(^\w[^\n]*$)+/m) do |x|
  x.gsub(/^(.+)$/, "\\1  ")
end

And here's what I've come up with so far in python 2.5:

def newline_callback(matchobj):
    return re.sub(r'^(.+)$','\1 ',matchobj.group(0))     
text = re.sub(r'(\A|^$\n)(^\w[^\n]*\n)(^\w[^\n]*$)+', newline_callback, text)

There just doesn't seem to be any effect at all :-/

If anyone has a fully working implementation of github flavored markdown in python, other than this one (doesn't seem to work for newlines), I'd love to hear about it. I'm really most concerned about the newlines.

These are the tests for the regex, from github's ruby code:

>>> gfm_pre_filter('apple\\npear\\norange\\n\\nruby\\npython\\nerlang')
'apple  \\npear  \\norange\\n\\nruby  \\npython  \\nerlang'
>>> gfm_pre_filter('test \\n\\n\\n something')
'test \\n\\n\\n something'
>>> gfm_pre_filter('# foo\\n# bar')
'# foo\\n# bar'
>>> gfm_pre_filter('* foo\\n* bar')
'* foo\\n* bar'

Please post an example of something that should work. What's expected and what you're really getting. — S.Lott
– S.Lott, Commented Jan 28, 2011 at 10:48

Tonttu · Accepted Answer · 2011-01-28 21:58:26Z

1

That Ruby version has multiline modifier in the regex, so you need to do the same in python:

def newline_callback(matchobj):
    return re.sub(re.compile(r'^(.+)$', re.M),r'\1  ',matchobj.group(0))     

text = re.sub(re.compile(r'(\A|^$\n)(^\w[^\n]*\n)(^\w[^\n]*$)+', re.M), newline_callback, text)

So that code will (like the Ruby version) add two spaces after before newline, except if we have two newlines (paragraph).

Are those test string you gave correct? That file you linked has this, and it works with that fixed code:

"apple\npear\norange\n\nruby\npython\nerlang"
->
"apple  \npear  \norange\n\nruby  \npython  \nerlang"

answered Jan 28, 2011 at 21:58

Tonttu

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2 Comments

Sudhir Jonathan Over a year ago

Thanks a ton... Could you point out to to me where the multiline modifier is in the Ruby regex? It's not /m, is it?

Tonttu Over a year ago

Yes it's that /m. /foo/m is a short of Regexp.new("foo", Regexp::MULTILINE), see "Regular Expression Options": ruby-doc.org/docs/ruby-doc-bundle/ProgrammingRuby/book/…

S.Lott · Accepted Answer · 2011-01-28 10:47:38Z

0

return re.sub(r'^(.+)$',r'\1 ',matchobj.group(0))
                       ^^^--------------------------- you forgot this.

answered Jan 28, 2011 at 10:47

S.Lott

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1 Comment

Sudhir Jonathan Over a year ago

Yes, but that didn't really solve the problem... I've added tests that need to pass when the regex is applied.

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