#!/usr/bin/env python """ Python-Markdown =============== Converts Markdown to HTML. Basic usage as a module: import markdown md = Markdown() html = md.convert(your_text_string) See for more information and instructions on how to extend the functionality of the script. (You might want to read that before you try modifying this file.) Started by [Manfred Stienstra](http://www.dwerg.net/). Continued and maintained by [Yuri Takhteyev](http://www.freewisdom.org), [Waylan Limberg](http://achinghead.com/) and [Artem Yunusov](http://blog.splyer.com). Contact: * * License: [GPL 2](http://www.gnu.org/copyleft/gpl.html) or BSD """ version = "2.0-alpha" version_info = (2,0,0, "beta") import re, sys, codecs, htmlentitydefs from urlparse import urlparse, urlunparse from logging import getLogger, StreamHandler, Formatter, \ DEBUG, INFO, WARN, ERROR, CRITICAL MESSAGE_THRESHOLD = CRITICAL # Configure debug message logger (the hard way - to support python 2.3) logger = getLogger('MARKDOWN') logger.setLevel(DEBUG) # This is restricted by handlers later console_hndlr = StreamHandler() formatter = Formatter('%(name)s-%(levelname)s: "%(message)s"') console_hndlr.setFormatter(formatter) console_hndlr.setLevel(MESSAGE_THRESHOLD) logger.addHandler(console_hndlr) def message(level, text): ''' A wrapper method for logging debug messages. ''' logger.log(level, text) def isstr(s): """ Check if it's string """ return isinstance(s, unicode) or isinstance(s, str) def importETree(): """ Import best variant of ElementTree and return module object """ cetree = None try: # Python 2.5+ import xml.etree.cElementTree as cetree except ImportError: try: # Python 2.5+ import xml.etree.ElementTree as etree except ImportError: try: # normal cElementTree install import cElementTree as cetree except ImportError: try: # normal ElementTree install import elementtree.ElementTree as etree except ImportError: message(CRITICAL, "Failed to import ElementTree from any known place") sys.exit(1) if cetree: if cetree.VERSION < "1.0": message(CRITICAL, "cElementTree version is too old, 1.0 and upper required") sys.exit(1) etree = cetree else: if etree.VERSION < "1.1": message(CRITICAL, "ElementTree version is too old, 1.1 and upper required") sys.exit(1) return etree """ElementTree module in extensions use: `from markdown import etree` to access to the ElemetTree module, do not import it by yourself""" etree = importETree() def indentETree(elem, level=0): """ Indent ElementTree before serialization """ if level > 1: i = "\n" + (level-1) * " " else: i = "\n" if len(elem): if not elem.text or not elem.text.strip(): elem.text = i + " " for e in elem: indentETree(e, level+1) if not e.tail or not e.tail.strip(): e.tail = i if level and (not elem.tail or not elem.tail.strip()): elem.tail = i # --------------- CONSTANTS YOU MIGHT WANT TO MODIFY ----------------- TAB_LENGTH = 4 # expand tabs to this many spaces ENABLE_ATTRIBUTES = True # @id = xyz -> <... id="xyz"> SMART_EMPHASIS = True # this_or_that does not become thisorthat HTML_REMOVED_TEXT = "[HTML_REMOVED]" # text used instead of HTML in safe mode RTL_BIDI_RANGES = ( (u'\u0590', u'\u07FF'), # from Hebrew to Nko (includes Arabic, Syriac and Thaana) (u'\u2D30', u'\u2D7F'), # Tifinagh ) # Unicode Reference Table: # 0590-05FF - Hebrew # 0600-06FF - Arabic # 0700-074F - Syriac # 0750-077F - Arabic Supplement # 0780-07BF - Thaana # 07C0-07FF - Nko BOMS = { 'utf-8': (codecs.BOM_UTF8, ), 'utf-16': (codecs.BOM_UTF16_LE, codecs.BOM_UTF16_BE), #'utf-32': (codecs.BOM_UTF32_LE, codecs.BOM_UTF32_BE) } def removeBOM(text, encoding): """ Used by `markdownFromFile` to remove a "byte order mark" from the begining of an utf-8, utf-16 or utf-32 encoded file. """ convert = isinstance(text, unicode) for bom in BOMS[encoding]: bom = convert and bom.decode(encoding) or bom if text.startswith(bom): return text.lstrip(bom) return text # The following constant specifies the name used in the usage # statement displayed for python versions lower than 2.3. (With # python2.3 and higher the usage statement is generated by optparse # and uses the actual name of the executable called.) EXECUTABLE_NAME_FOR_USAGE = "python markdown.py" # --------------- CONSTANTS YOU _SHOULD NOT_ HAVE TO CHANGE ---------- # placeholders STX = u'\u0002' # Use STX ("Start of text") for start-of-placeholder ETX = u'\u0003' # Use ETX ("End of text") for end-of-placeholder HTML_PLACEHOLDER_PREFIX = STX+"html:" HTML_PLACEHOLDER = HTML_PLACEHOLDER_PREFIX + "%d"+ETX INLINE_PLACEHOLDER_PREFIX = STX+"inline:" INLINE_PLACEHOLDER_SUFFIX = ETX AMP_SUBSTITUTE = STX+"amp"+ETX BLOCK_LEVEL_ELEMENTS = ['p', 'div', 'blockquote', 'pre', 'table', 'dl', 'ol', 'ul', 'script', 'noscript', 'form', 'fieldset', 'iframe', 'math', 'ins', 'del', 'hr', 'hr/', 'style'] def isBlockLevel (tag): """ Used by HTMLBlockPreprocessor to check if a given tag is a block level element. """ return ( (tag in BLOCK_LEVEL_ELEMENTS) or (tag[0] == 'h' and tag[1] in "0123456789") ) def codepoint2name(code): """ Return entity definition by code, or code if there is no such entity definition """ entity = htmlentitydefs.codepoint2name.get(code) if entity: return "%s%s;" % (AMP_SUBSTITUTE, entity) else: return "%s#%d;" % (AMP_SUBSTITUTE, code) def handleAttributes(text, parent): """ Handale attributes, e.g {@id=123} """ def attributeCallback(match): parent.set(match.group(1), match.group(2)) return RE.regExp['attr'].sub(attributeCallback, text) class AtomicString(str): "A string which should not be further processed." pass """ ====================================================================== ========================== PRE-PROCESSORS ============================ ====================================================================== Preprocessors munge source text before we start doing anything too complicated. There are two types of preprocessors: TextPreprocessor and Preprocessor. """ class TextPreprocessor: """ TextPreprocessors are run before the text is broken into lines. Each TextPreprocessor implements a "run" method that takes a pointer to a text string of the document, modifies it as necessary and returns either the same pointer or a pointer to a new string. TextPreprocessors must extend markdown.TextPreprocessor. """ def run(self, text): """ Each subclass of TextPreprocessor should override the `run` method, which takes the document text as a single string and returns the (possibly modified) document as a single string. """ pass class Preprocessor: """ Preprocessors are run after the text is broken into lines. Each preprocessor implements a "run" method that takes a pointer to a list of lines of the document, modifies it as necessary and returns either the same pointer or a pointer to a new list. Preprocessors must extend markdown.Preprocessor. """ def run(self, lines): """ Each subclass of Preprocessor should override the `run` method, which takes the document as a list of strings split by newlines and returns the (possibly modified) list of lines. """ pass class HtmlBlockPreprocessor(TextPreprocessor): """ Remove html blocks from the source text and store them for later retrieval. """ def _get_left_tag(self, block): return block[1:].replace(">", " ", 1).split()[0].lower() def _get_right_tag(self, left_tag, block): return block.rstrip()[-len(left_tag)-2:-1].lower() def _equal_tags(self, left_tag, right_tag): if left_tag == 'div' or left_tag[0] in ['?', '@', '%']: # handle PHP, etc. return True if ("/" + left_tag) == right_tag: return True if (right_tag == "--" and left_tag == "--"): return True elif left_tag == right_tag[1:] \ and right_tag[0] != "<": return True else: return False def _is_oneliner(self, tag): return (tag in ['hr', 'hr/']) def run(self, text): """ Find and remove raw html from text. """ new_blocks = [] text = text.split("\n\n") items = [] left_tag = '' right_tag = '' in_tag = False # flag for block in text: if block.startswith("\n"): block = block[1:] if not in_tag: if block.startswith("<"): left_tag = self._get_left_tag(block) right_tag = self._get_right_tag(left_tag, block) if not (isBlockLevel(left_tag) \ or block[1] in ["!", "?", "@", "%"]): new_blocks.append(block) continue if self._is_oneliner(left_tag): new_blocks.append(block.strip()) continue if block[1] == "!": # is a comment block left_tag = "--" right_tag = self._get_right_tag(left_tag, block) # keep checking conditions below and maybe just append if block.rstrip().endswith(">") \ and self._equal_tags(left_tag, right_tag): new_blocks.append( self.stash.store(block.strip())) continue else: #if not block[1] == "!": # if is block level tag and is not complete items.append(block.strip()) in_tag = True continue new_blocks.append(block) else: items.append(block.strip()) right_tag = self._get_right_tag(left_tag, block) if self._equal_tags(left_tag, right_tag): # if find closing tag in_tag = False new_blocks.append( self.stash.store('\n\n'.join(items))) items = [] if items: new_blocks.append(self.stash.store('\n\n'.join(items))) new_blocks.append('\n') return "\n\n".join(new_blocks) HTML_BLOCK_PREPROCESSOR = HtmlBlockPreprocessor() class HeaderPreprocessor(Preprocessor): """ Replace underlined headers with hashed headers to avoid the need for lookahead later. """ def run (self, lines): """ Find and replace underlined headers. """ i = -1 while i+1 < len(lines): i = i+1 if not lines[i].strip(): continue if lines[i].startswith("#"): lines.insert(i+1, "\n") if (i+1 <= len(lines) and lines[i+1] and lines[i+1][0] in ['-', '=']): underline = lines[i+1].strip() if underline == "="*len(underline): lines[i] = "# " + lines[i].strip() lines[i+1] = "" elif underline == "-"*len(underline): lines[i] = "## " + lines[i].strip() lines[i+1] = "" return lines HEADER_PREPROCESSOR = HeaderPreprocessor() class LinePreprocessor(Preprocessor): """ Convert HR lines to "___" format """ blockquote_re = re.compile(r'^(> )+') def run (self, lines): """ Find and replace HR lines. """ for i in range(len(lines)): prefix = '' m = self.blockquote_re.search(lines[i]) if m: prefix = m.group(0) if self._isLine(lines[i][len(prefix):]): lines[i] = prefix + "___" return lines def _isLine(self, block): """Determine if a block should be replaced with an
""" if block.startswith(" "): return False # a code block text = "".join([x for x in block if not x.isspace()]) if len(text) <= 2: return False for pattern in ['isline1', 'isline2', 'isline3']: m = RE.regExp[pattern].match(text) if (m and m.group(1)): return True else: return False LINE_PREPROCESSOR = LinePreprocessor() class ReferencePreprocessor(Preprocessor): """ Remove reference definitions from the text and store them for later use. """ def run (self, lines): """ Remove and store reference defs. """ new_text = []; for line in lines: m = RE.regExp['reference-def'].match(line) if m: id = m.group(2).strip().lower() t = m.group(4).strip() # potential title if not t: self.references[id] = (m.group(3), t) elif (len(t) >= 2 and (t[0] == t[-1] == "\"" or t[0] == t[-1] == "\'" or (t[0] == "(" and t[-1] == ")") ) ): self.references[id] = (m.group(3), t[1:-1]) else: new_text.append(line) else: new_text.append(line) return new_text #+ "\n" REFERENCE_PREPROCESSOR = ReferencePreprocessor() """ ====================================================================== ========================== INLINE PATTERNS =========================== ====================================================================== Inline patterns such as *emphasis* are handled by means of auxiliary objects, one per pattern. Pattern objects must be instances of classes that extend markdown.Pattern. Each pattern object uses a single regular expression and needs support the following methods: pattern.getCompiledRegExp() - returns a regular expression pattern.handleMatch(m) - takes a match object and returns a ElementTree element or just plain text All of python markdown's built-in patterns subclass from Pattern, but you can add additional patterns that don't. Also note that all the regular expressions used by inline must capture the whole block. For this reason, they all start with '^(.*)' and end with '(.*)!'. In case with built-in expression Pattern takes care of adding the "^(.*)" and "(.*)!". Finally, the order in which regular expressions are applied is very important - e.g. if we first replace http://.../ links with tags and _then_ try to replace inline html, we would end up with a mess. So, we apply the expressions in the following order: * escape and backticks have to go before everything else, so that we can preempt any markdown patterns by escaping them. * then we handle auto-links (must be done before inline html) * then we handle inline HTML. At this point we will simply replace all inline HTML strings with a placeholder and add the actual HTML to a hash. * then inline images (must be done before links) * then bracketed links, first regular then reference-style * finally we apply strong and emphasis """ NOBRACKET = r'[^\]\[]*' BRK = ( r'\[(' + (NOBRACKET + r'(\[')*6 + (NOBRACKET+ r'\])*')*6 + NOBRACKET + r')\]' ) NOIMG = r'(?|((?:(?:\(.*?\))|[^\(\)]))*?)\s*((['"])(.*)\12)?\)''' # [text](url) or [text]() IMAGE_LINK_RE = r'\!' + BRK + r'\s*\((<.*?>|([^\)]*))\)' # ![alttxt](http://x.com/) or ![alttxt]() REFERENCE_RE = NOIMG + BRK+ r'\s*\[([^\]]*)\]' # [Google][3] IMAGE_REFERENCE_RE = r'\!' + BRK + '\s*\[([^\]]*)\]' # ![alt text][2] NOT_STRONG_RE = r'( \* )' # stand-alone * or _ AUTOLINK_RE = r'<((?:f|ht)tps?://[^>]*)>' # AUTOMAIL_RE = r'<([^> \!]*@[^> ]*)>' # HTML_RE = r'(\<([a-zA-Z/][^\>]*?|\!--.*?--)\>)' # <...> ENTITY_RE = r'(&[\#a-zA-Z0-9]*;)' # & LINE_BREAK_RE = r' \n' # two spaces at end of line LINE_BREAK_2_RE = r' $' # two spaces at end of text class Pattern: """Base class that inline patterns subclass. """ def __init__ (self, pattern): """ Create an instant of an inline pattern. Keyword arguments: * pattern: A regular expression that matches a pattern """ self.pattern = pattern self.compiled_re = re.compile("^(.*?)%s(.*?)$" % pattern, re.DOTALL) # Api for Markdown to pass safe_mode into instance self.safe_mode = False def getCompiledRegExp (self): """ Return a compiled regular expression. """ return self.compiled_re def handleMatch(self, m): """ Return a ElementTree element from the given match. Subclasses should override this method. Keyword arguments: * m: A re match object containing a match of the pattern. """ pass def type(self): """ Return class name, to define pattern type """ return self.__class__.__name__ BasePattern = Pattern # for backward compatibility class SimpleTextPattern (Pattern): """ Return a simple text of group(2) of a Pattern. """ def handleMatch(self, m): text = m.group(2) if text == INLINE_PLACEHOLDER_PREFIX: return None return text class SimpleTagPattern (Pattern): """ Return element of type `tag` with a text attribute of group(3) of a Pattern. """ def __init__ (self, pattern, tag): Pattern.__init__(self, pattern) self.tag = tag def handleMatch(self, m): el = etree.Element(self.tag) el.text = m.group(3) return el class SubstituteTagPattern (SimpleTagPattern): """ Return a eLement of type `tag` with no children. """ def handleMatch (self, m): return etree.Element(self.tag) class BacktickPattern (Pattern): """ Return a `` element containing the matching text. """ def __init__ (self, pattern): Pattern.__init__(self, pattern) self.tag = "code" def handleMatch(self, m): el = etree.Element(self.tag) el.text = m.group(3).strip() return el class DoubleTagPattern (SimpleTagPattern): """ Return a ElementTree element nested in tag2 nested in tag1. Useful for strong emphasis etc. """ def handleMatch(self, m): tag1, tag2 = self.tag.split(",") el1 = etree.Element(tag1) el2 = etree.SubElement(el1, tag2) el2.text = m.group(3) return el1 class HtmlPattern (Pattern): """ Store raw inline html and return a placeholder. """ def handleMatch (self, m): rawhtml = m.group(2) inline = True place_holder = self.stash.store(rawhtml) return place_holder class LinkPattern (Pattern): """ Return a link element from the given match. """ def handleMatch(self, m): el = etree.Element("a") el.text = m.group(2) title = m.group(11) href = m.group(9) if href: if href[0] == "<": href = href[1:-1] el.set("href", self.sanatize_url(href.strip())) else: el.set("href", "") if title: title = dequote(title) #.replace('"', """) el.set("title", title) return el def sanatize_url(self, url): """ Sanitize a url against xss attacks in "safe_mode". Rather than specifically blacklisting `javascript:alert("XSS")` and all its aliases (see ), we whitelist known safe url formats. Most urls contain a network location, however some are known not to (i.e.: mailto links). Script urls do not contain a location. Additionally, for `javascript:...`, the scheme would be "javascript" but some aliases will appear to `urlparse()` to have no scheme. On top of that relative links (i.e.: "foo/bar.html") have no scheme. Therefore we must check "path", "parameters", "query" and "fragment" for any literal colons. We don't check "scheme" for colons because it *should* never have any and "netloc" must allow the form: `username:password@host:port`. """ locless_schemes = ['', 'mailto', 'news'] scheme, netloc, path, params, query, fragment = url = urlparse(url) safe_url = False if netloc != '' or scheme in locless_schemes: safe_url = True for part in url[2:]: if ":" in part: safe_url = False if self.safe_mode and not safe_url: return '' else: return urlunparse(url) class ImagePattern(LinkPattern): """ Return a img element from the given match. """ def handleMatch(self, m): el = etree.Element("img") src_parts = m.group(9).split() if src_parts: src = src_parts[0] if src[0] == "<" and src[-1] == ">": src = src[1:-1] el.set('src', self.sanatize_url(src)) else: el.set('src', "") if len(src_parts) > 1: el.set('title', dequote(" ".join(src_parts[1:]))) if ENABLE_ATTRIBUTES: truealt = handleAttributes(m.group(2), el) else: truealt = m.group(2) el.set('alt', truealt) return el class ReferencePattern(LinkPattern): """ Match to a stored reference and return link element. """ def handleMatch(self, m): if m.group(9): id = m.group(9).lower() else: # if we got something like "[Google][]" # we'll use "google" as the id id = m.group(2).lower() if not self.references.has_key(id): # ignore undefined refs return None href, title = self.references[id] text = m.group(2) return self.makeTag(href, title, text) def makeTag(self, href, title, text): el = etree.Element('a') el.set('href', self.sanatize_url(href)) if title: el.set('title', title) el.text = text return el class ImageReferencePattern (ReferencePattern): """ Match to a stored reference and return img element. """ def makeTag(self, href, title, text): el = etree.Element("img") el.set("src", self.sanatize_url(href)) if title: el.set("title", title) el.set("alt", text) return el class AutolinkPattern (Pattern): """ Return a link Element given an autolink (``). """ def handleMatch(self, m): el = etree.Element("a") el.set('href', m.group(2)) el.text = AtomicString(m.group(2)) return el class AutomailPattern (Pattern): """ Return a mailto link Element given an automail link (``). """ def handleMatch(self, m): el = etree.Element('a') email = m.group(2) if email.startswith("mailto:"): email = email[len("mailto:"):] letters = [codepoint2name(ord(letter)) for letter in email] el.text = AtomicString(''.join(letters)) mailto = "mailto:" + email mailto = "".join([AMP_SUBSTITUTE + '#%d;' % ord(letter) for letter in mailto]) el.set('href', mailto) return el ESCAPE_PATTERN = SimpleTextPattern(ESCAPE_RE) NOT_STRONG_PATTERN = SimpleTextPattern(NOT_STRONG_RE) BACKTICK_PATTERN = BacktickPattern(BACKTICK_RE) STRONG_PATTERN = SimpleTagPattern(STRONG_RE, 'strong') EMPHASIS_PATTERN = SimpleTagPattern(EMPHASIS_RE, 'em') EMPHASIS_PATTERN_2 = SimpleTagPattern(EMPHASIS_2_RE, 'em') STRONG_EM_PATTERN = DoubleTagPattern(STRONG_EM_RE, 'strong,em') LINE_BREAK_PATTERN = SubstituteTagPattern(LINE_BREAK_RE, 'br ') LINE_BREAK_PATTERN_2 = SubstituteTagPattern(LINE_BREAK_2_RE, 'br ') LINK_PATTERN = LinkPattern(LINK_RE) IMAGE_LINK_PATTERN = ImagePattern(IMAGE_LINK_RE) IMAGE_REFERENCE_PATTERN = ImageReferencePattern(IMAGE_REFERENCE_RE) REFERENCE_PATTERN = ReferencePattern(REFERENCE_RE) HTML_PATTERN = HtmlPattern(HTML_RE) ENTITY_PATTERN = HtmlPattern(ENTITY_RE) AUTOLINK_PATTERN = AutolinkPattern(AUTOLINK_RE) AUTOMAIL_PATTERN = AutomailPattern(AUTOMAIL_RE) """ ====================================================================== ========================== POST-PROCESSORS =========================== ====================================================================== Markdown also allows post-processors, which are similar to preprocessors in that they need to implement a "run" method. However, they are run after core processing. There are two types of post-processors: Postprocessor and TextPostprocessor """ class Postprocessor: """ Postprocessors are run before the ElementTree serialization. Each Postprocessor implements a "run" method that takes a pointer to a ElementTree, modifies it as necessary and returns a ElementTree document. Postprocessors must extend markdown.Postprocessor. There are currently no standard post-processors, but the footnote extension uses one. """ def run(self, root): """ Subclasses of Postprocessor should implement a `run` method, which takes a root Element. Method can return another Element, and global root Element will be replaced, or just modify current and return None. """ pass class TextPostprocessor: """ TextPostprocessors are run after the ElementTree it converted back into text. Each TextPostprocessor implements a "run" method that takes a pointer to a text string, modifies it as necessary and returns a text string. TextPostprocessors must extend markdown.TextPostprocessor. """ def run(self, text): """ Subclasses of TextPostprocessor should implement a `run` method, which takes the html document as a single text string and returns a (possibly modified) string. """ pass class RawHtmlTextPostprocessor(TextPostprocessor): """ Restore raw html to the document. """ def __init__(self): pass def run(self, text): """ Iterate over html stash and restore "safe" html. """ for i in range(self.stash.html_counter): html, safe = self.stash.rawHtmlBlocks[i] if self.safeMode and not safe: if str(self.safeMode).lower() == 'escape': html = self.escape(html) elif str(self.safeMode).lower() == 'remove': html = '' else: html = HTML_REMOVED_TEXT text = text.replace("

%s\n

" % (HTML_PLACEHOLDER % i), html + "\n") text = text.replace(HTML_PLACEHOLDER % i, html) return text def escape(self, html): """ Basic html escaping """ html = html.replace('&', '&') html = html.replace('<', '<') html = html.replace('>', '>') return html.replace('"', '"') RAWHTMLTEXTPOSTPROCESSOR = RawHtmlTextPostprocessor() class AndSubstitutePostprocessor(TextPostprocessor): """ Restore valid entities """ def __init__(self): pass def run(self, text): text = text.replace(AMP_SUBSTITUTE, "&") return text AMPSUBSTITUTETEXTPOSTPROCESSOR = AndSubstitutePostprocessor() """ ====================================================================== ========================== MISC AUXILIARY CLASSES ==================== ====================================================================== """ class HtmlStash: """ This class is used for stashing HTML objects that we extract in the beginning and replace with place-holders. """ def __init__ (self): """ Create a HtmlStash. """ self.html_counter = 0 # for counting inline html segments self.rawHtmlBlocks=[] def store(self, html, safe=False): """ Saves an HTML segment for later reinsertion. Returns a placeholder string that needs to be inserted into the document. Keyword arguments: * html: an html segment * safe: label an html segment as safe for safemode Returns : a placeholder string """ self.rawHtmlBlocks.append((html, safe)) placeholder = HTML_PLACEHOLDER % self.html_counter self.html_counter += 1 return placeholder def rest(self): self.html_counter = 0 self.rawHtmlBlocks = [] class BlockGuru: """ Parse document for block level constructs (paragraphs, lists, etc.).""" def _findHead(self, lines, fn, allowBlank=0): """ Functional magic to help determine boundaries of indented blocks. Keyword arguments: * lines: an array of strings * fn: a function that returns a substring of a string if the string matches the necessary criteria * allowBlank: specifies whether it's ok to have blank lines between matching functions Returns: a list of post processes items and the unused remainder of the original list """ items = [] item = -1 i = 0 # to keep track of where we are for line in lines: if not line.strip() and not allowBlank: return items, lines[i:] if not line.strip() and allowBlank: # If we see a blank line, this _might_ be the end i += 1 # Find the next non-blank line for j in range(i, len(lines)): if lines[j].strip(): next = lines[j] break else: # There is no more text => this is the end break # Check if the next non-blank line is still a part of the list part = fn(next) if part: items.append("") continue else: break # found end of the list part = fn(line) if part: items.append(part) i += 1 continue else: return items, lines[i:] else: i += 1 return items, lines[i:] def detabbed_fn(self, line): """ An auxiliary method to be passed to _findHead """ m = RE.regExp['tabbed'].match(line) if m: return m.group(4) else: return None def detectTabbed(self, lines): """ Find indented text and remove indent before further proccesing. """ return self._findHead(lines, self.detabbed_fn, allowBlank = 1) def dequote(string): """ Removes quotes from around a string """ if ( ( string.startswith('"') and string.endswith('"')) or (string.startswith("'") and string.endswith("'")) ): return string[1:-1] else: return string class InlineStash: def __init__(self): """ Create a InlineStash. """ self.prefix = INLINE_PLACEHOLDER_PREFIX self.suffix = INLINE_PLACEHOLDER_SUFFIX self._nodes = {} self.phLength = 4 + len(self.prefix) + len(self.suffix) def _genPlaceholder(self, type): """ Generate a placeholder """ id = "%04d" % len(self._nodes) hash = "%s%s:%s%s" % (self.prefix, type, id, self.suffix) return hash, id def extractId(self, data, index): """ Extract id from data string, start from index Keyword arguments: * data: string * index: index, from which we start search Returns: placeholder id and string index, after found placeholder """ endIndex = data.find(self.suffix, index+1) if endIndex == -1: return None, index + 1 else: pair = data[index + len(self.prefix): endIndex].split(":") if len(pair) == 2: return pair[1], endIndex + len(self.suffix) else: return None, index + 1 def isin(self, id): return self._nodes.has_key(id) def get(self, id): """ Return node by id """ return self._nodes.get(id) def add(self, node, type): """ Add node to stash """ pholder, id = self._genPlaceholder(type) self._nodes[id] = node return pholder def rest(self): """ Reset instance """ self._nodes = {} """ ====================================================================== ========================== CORE MARKDOWN ============================= ====================================================================== This stuff is hard, so if you are thinking of extending the syntax, see first if you can do it via pre-processors, post-processors, inline patterns or a combination of the three. """ class CorePatterns: """ This class is scheduled for removal as part of a refactoring effort. """ patterns = { 'header': r'(#{1,6})[ \t]*(.*?)[ \t]*(#*)', # # A title 'reference-def': r'(\ ?\ ?\ ?)\[([^\]]*)\]:\s*([^ ]*)(.*)', # [Google]: http://www.google.com/ 'containsline': r'([-]*)$|^([=]*)', # -----, =====, etc. 'ol': r'[ ]{0,3}[\d]*\.\s+(.*)', # 1. text 'ul': r'[ ]{0,3}[*+-]\s+(.*)', # "* text" 'isline1': r'(\**)', # *** 'isline2': r'(\-*)', # --- 'isline3': r'(\_*)', # ___ 'tabbed': r'((\t)|( ))(.*)', # an indented line 'quoted': r'[ ]{0,2}> ?(.*)', # a quoted block ("> ...") } def __init__ (self): self.regExp = {} for key in self.patterns.keys(): self.regExp[key] = re.compile("^%s$" % self.patterns[key], re.DOTALL) self.regExp['containsline'] = re.compile(r'^([-]*)$|^([=]*)$', re.M) self.regExp['attr'] = re.compile("\{@([^\}]*)=([^\}]*)}") # {@id=123} RE = CorePatterns() class Markdown: """ Markdown formatter class for creating an html document from Markdown text. """ def __init__(self, extensions=[], extension_configs={}, safe_mode = False): """ Creates a new Markdown instance. Keyword arguments: * extensions: A list of extensions. If they are of type string, the module mdx_name.py will be loaded. If they are a subclass of markdown.Extension, they will be used as-is. * extension-configs: Configuration setting for extensions. * safe_mode: Disallow raw html. One of "remove", "replace" or "escape". """ self.source = None self.safeMode = safe_mode self.blockGuru = BlockGuru() self.registeredExtensions = [] self.docType = "" self.stripTopLevelTags = True self.textPreprocessors = [HTML_BLOCK_PREPROCESSOR] self.preprocessors = [HEADER_PREPROCESSOR, LINE_PREPROCESSOR, # A footnote preprocessor will # get inserted here REFERENCE_PREPROCESSOR] self.postprocessors = [] # a footnote postprocessor will get # inserted later self.textPostprocessors = [# a footnote postprocessor will get # inserted here RAWHTMLTEXTPOSTPROCESSOR, AMPSUBSTITUTETEXTPOSTPROCESSOR] self.prePatterns = [] self.inlinePatterns = [ BACKTICK_PATTERN, ESCAPE_PATTERN, REFERENCE_PATTERN, LINK_PATTERN, IMAGE_LINK_PATTERN, IMAGE_REFERENCE_PATTERN, AUTOLINK_PATTERN, AUTOMAIL_PATTERN, LINE_BREAK_PATTERN_2, LINE_BREAK_PATTERN, HTML_PATTERN, ENTITY_PATTERN, NOT_STRONG_PATTERN, STRONG_EM_PATTERN, STRONG_PATTERN, EMPHASIS_PATTERN, EMPHASIS_PATTERN_2 # The order of the handlers matters!!! ] self.inlineStash = InlineStash() self.references = {} self.htmlStash = HtmlStash() self.registerExtensions(extensions = extensions, configs = extension_configs) self.reset() def registerExtensions(self, extensions, configs): """ Register extensions with this instance of Markdown. Keyword aurguments: * extensions: A list of extensions, which can either be strings or objects. See the docstring on Markdown. * configs: A dictionary mapping module names to config options. """ for ext in extensions: if isinstance(ext, basestring): ext = load_extension(ext, configs.get(ext, [])) elif hasattr(ext, 'extendMarkdown'): # Looks like an Extension. # Nothing to do here. pass else: message(ERROR, "Incorrect type! Extension '%s' is " "neither a string or an Extension." %(repr(ext))) continue ext.extendMarkdown(self, globals()) def registerExtension(self, extension): """ This gets called by the extension """ self.registeredExtensions.append(extension) def reset(self): """ Resets all state variables so that we can start with a new text. """ self.inlineStash.rest() self.htmlStash.rest() self.references.clear() HTML_BLOCK_PREPROCESSOR.stash = self.htmlStash LINE_PREPROCESSOR.stash = self.htmlStash REFERENCE_PREPROCESSOR.references = self.references HTML_PATTERN.stash = self.htmlStash ENTITY_PATTERN.stash = self.htmlStash REFERENCE_PATTERN.references = self.references IMAGE_REFERENCE_PATTERN.references = self.references RAWHTMLTEXTPOSTPROCESSOR.stash = self.htmlStash RAWHTMLTEXTPOSTPROCESSOR.safeMode = self.safeMode for extension in self.registeredExtensions: extension.reset() for pattern in self.inlinePatterns: pattern.safe_mode = self.safeMode def _transform(self): """Transform the Markdown text into a XHTML body document. Returns: ElementTree object """ # Setup the document self.root = etree.Element("span") # Split into lines and run the preprocessors that will work with # self.lines self.lines = self.source.split("\n") # Run the pre-processors on the lines for prep in self.preprocessors : self.lines = prep.run(self.lines) # Create a ElementTree from the lines buffer = [] for line in self.lines: if line.startswith("#"): self._processSection(self.root, buffer) buffer = [line] else: buffer.append(line) self._processSection(self.root, buffer) return etree.ElementTree(self.root) def _processSection(self, parent_elem, lines, inList=0, looseList=0): """ Process a section of a source document, looking for high level structural elements like lists, block quotes, code segments, html blocks, etc. Some those then get stripped of their high level markup (e.g. get unindented) and the lower-level markup is processed recursively. Keyword arguments: * parent_elem: A ElementTree element to which the content will be added. * lines: a list of lines * inList: a level Returns: None """ # Loop through lines until none left. while lines: # Skipping empty line if not lines[0]: lines = lines[1:] continue # Check if this section starts with a list, a blockquote or # a code block processFn = { 'ul': self._processUList, 'ol': self._processOList, 'quoted': self._processQuote, 'tabbed': self._processCodeBlock} for regexp in ['ul', 'ol', 'quoted', 'tabbed']: m = RE.regExp[regexp].match(lines[0]) if m: processFn[regexp](parent_elem, lines, inList) return # We are NOT looking at one of the high-level structures like # lists or blockquotes. So, it's just a regular paragraph # (though perhaps nested inside a list or something else). If # we are NOT inside a list, we just need to look for a blank # line to find the end of the block. If we ARE inside a # list, however, we need to consider that a sublist does not # need to be separated by a blank line. Rather, the following # markup is legal: # # * The top level list item # # Another paragraph of the list. This is where we are now. # * Underneath we might have a sublist. # if inList: start, lines = self._linesUntil(lines, (lambda line: RE.regExp['ul'].match(line) or RE.regExp['ol'].match(line) or not line.strip())) self._processSection(parent_elem, start, inList - 1, looseList = looseList) inList = inList-1 else: # Ok, so it's just a simple block paragraph, lines = self._linesUntil(lines, lambda line: not line.strip() or line[0] == '>') if len(paragraph) and paragraph[0].startswith('#'): self._processHeader(parent_elem, paragraph) elif len(paragraph) and \ RE.regExp["isline3"].match(paragraph[0]): self._processHR(parent_elem) lines = paragraph[1:] + lines elif paragraph: self._processParagraph(parent_elem, paragraph, inList, looseList) if lines and not lines[0].strip(): lines = lines[1:] # skip the first (blank) line def _processHR(self, parentElem): hr = etree.SubElement(parentElem, "hr") def _processHeader(self, parentElem, paragraph): m = RE.regExp['header'].match(paragraph[0]) if m: level = len(m.group(1)) h = etree.SubElement(parentElem, "h%d" % level) inline = etree.SubElement(h, "inline") inline.text = m.group(2).strip() else: message(CRITICAL, "We've got a problem header!") def _processParagraph(self, parentElem, paragraph, inList, looseList): if ( parentElem.tag == 'li' and not (looseList or parentElem.getchildren())): # If this is the first paragraph inside "li", don't # put

around it - append the paragraph bits directly # onto parentElem el = parentElem else: # Otherwise make a "p" element el = etree.SubElement(parentElem, "p") dump = [] # Searching for hr for line in paragraph: if RE.regExp["isline3"].match(line): inline = etree.SubElement(el, "inline") inline.text = "\n".join(dump) etree.SubElement(el, "hr") dump.clear() else: dump.append(line) if dump: text = "\n".join(dump) inline = etree.SubElement(el, "inline") inline.text = text def _processUList(self, parentElem, lines, inList): self._processList(parentElem, lines, inList, listexpr='ul', tag = 'ul') def _processOList(self, parentElem, lines, inList): self._processList(parentElem, lines, inList, listexpr='ol', tag = 'ol') def _processList(self, parentElem, lines, inList, listexpr, tag): """ Given a list of document lines starting with a list item, finds the end of the list, breaks it up, and recursively processes each list item and the remainder of the text file. Keyword arguments: * parentElem: A ElementTree element to which the content will be added * lines: a list of lines * inList: a level Returns: None """ ul = etree.SubElement(parentElem, tag) # ul might actually be '

    ' looseList = 0 # Make a list of list items items = [] item = -1 i = 0 # a counter to keep track of where we are for line in lines: loose = 0 if not line.strip(): # If we see a blank line, this _might_ be the end of the list i += 1 loose = 1 # Find the next non-blank line for j in range(i, len(lines)): if lines[j].strip(): next = lines[j] break else: # There is no more text => end of the list break # Check if the next non-blank line is still a part of the list if ( RE.regExp[listexpr].match(next) or RE.regExp['tabbed'].match(next) ): # get rid of any white space in the line items[item].append(line.strip()) looseList = loose or looseList continue else: break # found end of the list # Now we need to detect list items (at the current level) # while also detabing child elements if necessary for expr in ['ul', 'ol', 'tabbed']: m = RE.regExp[expr].match(line) if m: if expr in ['ul', 'ol']: # We are looking at a new item #if m.group(1) : # Removed the check to allow for a blank line # at the beginning of the list item items.append([m.group(1)]) item += 1 elif expr == 'tabbed': # This line needs to be detabbed items[item].append(m.group(4)) #after the 'tab' i += 1 break else: items[item].append(line) # Just regular continuation i += 1 # added on 2006.02.25 else: i += 1 # Add the ElementTree elements for item in items: li = etree.SubElement(ul, "li") self._processSection(li, item, inList + 1, looseList = looseList) # Process the remaining part of the section self._processSection(parentElem, lines[i:], inList) def _linesUntil(self, lines, condition): """ A utility function to break a list of lines upon the first line that satisfied a condition. The condition argument should be a predicate function. """ i = -1 for line in lines: i += 1 if condition(line): break else: i += 1 return lines[:i], lines[i:] def _processQuote(self, parentElem, lines, inList): """ Given a list of document lines starting with a quote finds the end of the quote, unindents it and recursively processes the body of the quote and the remainder of the text file. Keyword arguments: * parentElem: ElementTree element to which the content will be added * lines: a list of lines * inList: a level Returns: None """ dequoted = [] i = 0 blank_line = False # allow one blank line between paragraphs for line in lines: m = RE.regExp['quoted'].match(line) if m: dequoted.append(m.group(1)) i += 1 blank_line = False elif not blank_line and line.strip() != '': dequoted.append(line) i += 1 elif not blank_line and line.strip() == '': dequoted.append(line) i += 1 blank_line = True else: break blockquote = etree.SubElement(parentElem, "blockquote") self._processSection(blockquote, dequoted, inList) self._processSection(parentElem, lines[i:], inList) def _processCodeBlock(self, parentElem, lines, inList): """ Given a list of document lines starting with a code block finds the end of the block, puts it into the ElementTree verbatim wrapped in ("
    ") and recursively processes the
            the remainder of the text file.
    
            Keyword arguments:
            
            * parentElem: ElementTree element to which the content will be added
            * lines: a list of lines
            * inList: a level
            
            Returns: None
            
            """
    
            detabbed, theRest = self.blockGuru.detectTabbed(lines)
    
            pre = etree.SubElement(parentElem, "pre")
            code = etree.SubElement(pre, "code")
            
            text = "\n".join(detabbed).rstrip()+"\n"
            code.text = text
            self._processSection(parentElem, theRest, inList)        
            
        def _handleInline(self, data, patternIndex=0):
            """
            Process string with inline patterns and replace it
            with placeholders
    
            Keyword arguments:
            
            * data: A line of Markdown text
            * patternIndex: The index of the inlinePattern to start with
            
            Returns: String with placeholders. 
            
            """
    
            if isinstance(data, AtomicString):
                return data
    
            startIndex = 0
            
            while patternIndex < len(self.inlinePatterns):
                
                data, matched, startIndex = self._applyInline(
                                                 self.inlinePatterns[patternIndex],
                                                 data, patternIndex, startIndex)
                
                if not matched:
                    patternIndex += 1
    
            return data
        
        def _applyInline(self, pattern, data, patternIndex, startIndex=0):
            """ 
            Check if the line fits the pattern, create the necessary 
            elements, add it to InlineStash
            
            Keyword arguments:
            
            * data: the text to be processed
            * pattern: the pattern to be checked
            * patternIndex: index of current pattern
            * startIndex: string index, from which we starting search
    
            Returns: String with placeholders instead of ElementTree elements.
            """
            match = pattern.getCompiledRegExp().match(data[startIndex:])
            leftData = data[:startIndex]
     
            if not match:
                return data, False, 0
    
            node = pattern.handleMatch(match)
         
            if node is None:
                return data, True, len(leftData) + match.span(len(match.groups()))[0]
            
            if not isstr(node):            
                if not node.tag in ["code", "pre"]:
                    # We need to process current node too
                    for child in [node] + node.getchildren():
                        if not isstr(node):
                            if child.text:
                                child.text = self._handleInline(child.text, 
                                                                patternIndex + 1)
                            if child.tail:
                                child.tail = self._handleInline(child.tail, 
                                                                patternIndex)
       
            pholder = self.inlineStash.add(node, pattern.type())
    
            return "%s%s%s%s" % (leftData, 
                                 match.group(1), 
                                 pholder, match.groups()[-1]), True, 0
       
        def _processElementText(self, node, subnode, isText=True):
            """
            Process placeholders in Element.text or Element.tail
            of Elements popped from InlineStash
            
            Keywords arguments:
            
            * node: parent node
            * subnode: processing node
            * isText: bool variable, True - it's text, False - it's tail
            
            Returns: None
            
            """       
            if isText:
                text = subnode.text
                subnode.text = None
            else:
                text = subnode.tail
                subnode.tail = None
            
            childResult = self._processPlaceholders(text, subnode)
            
            if not isText and node is not subnode:
                pos = node.getchildren().index(subnode)
                node.remove(subnode)
            else:
                pos = 0
                
            childResult.reverse()
            for newChild in childResult:
                node.insert(pos, newChild)
        
        def _processPlaceholders(self, data, parent):
            """
            Process string with placeholders and generate ElementTree tree.
            
            Keyword arguments:
            
            * data: string with placeholders instead of ElementTree elements.
            * parent: Element, which contains processing inline data
    
            Returns: list with ElementTree elements with applied inline patterns.
            """
            
            def linkText(text):
                if text:
                    if result:
                        if result[-1].tail:
                            result[-1].tail += text
                        else:
                            result[-1].tail = text
                    else:
                        if parent.text:
                            parent.text += text
                        else:
                            parent.text = text
                
            result = []
            prefix = self.inlineStash.prefix
            strartIndex = 0
        
            while data:
                
                index = data.find(prefix, strartIndex)
                if index != -1:
                    
                    id, phEndIndex = self.inlineStash.extractId(data, index)
                    
                    if self.inlineStash.isin(id):
       
                        node = self.inlineStash.get(id)
                 
                        if index > 0:
                            text = data[strartIndex:index]
                            linkText(text)
              
                        if not isstr(node): # it's Element
                            
                            for child in [node] + node.getchildren():
                
                                if child.tail:
                                    if child.tail.strip():
                                        self._processElementText(node, child, False)
                                
                                if child.text:
                                    if child.text.strip():
                                        self._processElementText(child, child)
                            
                        else: # it's just a string
                    
                            linkText(node)
                            strartIndex = phEndIndex
                            continue
                        
                        strartIndex = phEndIndex    
                        result.append(node)
                           
                    else: # wrong placeholder
                        end = index + len(prefix)
                        linkText(data[strartIndex:end])
                        strartIndex = end 
                else:
                    
                    text = data[strartIndex:]
                    linkText(text)
                    data = ""
    
            return result
        
        
        def applyInlinePatterns(self, markdownTree):
            """
            Iterate over ElementTree, find elements with inline tag, 
            apply inline patterns and append newly created Elements to tree 
            
            Keyword arguments:
            
            * markdownTree: ElementTree object, representing Markdown tree.
    
            Returns: ElementTree object with applied inline patterns.
            """
     
            el = markdownTree.getroot()
                    
            stack = [el]
    
            while stack:
                currElement = stack.pop()
                insertQueue = []
                for child in currElement.getchildren():
                    
                    if child.tag == "inline":
    
                        lst = self._processPlaceholders(self._handleInline(
                                                        child.text), currElement)
                        stack += lst
                        
                        pos = currElement.getchildren().index(child)
                        
                        insertQueue.append((child, pos, lst))
                        
                    else:
                        stack.append(child) 
    
                          
                for element, pos, lst in insertQueue:
                    currElement.remove(element)
                    if currElement.text:
                        currElement.text = handleAttributes(currElement.text, 
                                                            currElement)
                    for newChild in lst:
                        # Processing attributes
                        if newChild.tail:
                            newChild.tail = handleAttributes(newChild.tail, 
                                                             currElement)
                        if newChild.text:
                            newChild.text = handleAttributes(newChild.text, 
                                                             newChild)
                        currElement.insert(pos, newChild)
                        pos += 1 
                
            return markdownTree
    
            
        def markdownToTree(self, source=None):
            """
            Create ElementTree, without applying inline paterns, 
            all data, include all data, that must be procesed wit inline 
            patterns in  sections.
            
            Keyword arguments:
            
            * source: An ascii or unicode string of Markdown formated text.
    
            Returns: ElementTree object.
            """
            if source is not None: #Allow blank string
                self.source = source
                
            if not self.source:
                return u""
            
            try:
                self.source = unicode(self.source)
            except UnicodeDecodeError:
                message(CRITICAL, 'UnicodeDecodeError: Markdown only accepts unicode or ascii  input.')
                return u""
            
            # Fixup the source text
    
            self.source = self.source.replace(STX, "")
            self.source = self.source.replace(ETX, "")
    
            self.source = self.source.replace("\r\n", "\n").replace("\r", "\n")
            self.source += "\n\n"
            self.source = self.source.expandtabs(TAB_LENGTH)
    
            for pp in self.textPreprocessors:
                self.source = pp.run(self.source)
            
            markdownTree = self._transform()
            
            return markdownTree      
    
        def convert (self, source=None):
            """
            Create the document in XHTML format.
    
            Keyword arguments:
            
            * source: An ascii or unicode string of Markdown formated text.
    
            Returns: A serialized XHTML body.
    
            """
    
            tree = self.markdownToTree(source)
    
            root = self.applyInlinePatterns(tree).getroot()
    
            # Run the post-processors
            for postprocessor in self.postprocessors:
                postprocessor.stash = self.htmlStash
                newRoot = postprocessor.run(root)
                if newRoot:
                    root = newRoot
    
            indentETree(root)
    
            xml, length = codecs.utf_8_decode(etree.tostring(root, encoding="utf8"))
            
            if self.stripTopLevelTags:
                xml = xml.strip()[44:-7] + "\n"
    
            # Run the text post-processors
            for pp in self.textPostprocessors:
                xml = pp.run(xml)
    
            return xml.strip()
    
    
        def __str__(self):
            ''' Report info about instance. Markdown always returns unicode. '''
    
            if self.source is None:
                status = 'in which no source text has been assinged.'
            else:
                status = 'which contains %d chars and %d line(s) of source.'%\
                         (len(self.source), self.source.count('\n')+1)
            return 'An instance of "%s" %s'% (self.__class__, status)
    
        __unicode__ = convert # markdown should always return a unicode string
    
    
    
    
    
    # ====================================================================
    
    def markdownFromFile(input = None,
                         output = None,
                         extensions = [],
                         encoding = None,
                         message_threshold = CRITICAL,
                         safe = False):
        """
        Convenience wrapper function that takes a filename as input.
    
        Used from the command-line, although may be useful in other situations. 
        Decodes the file using the provided encoding (defaults to utf-8), passes 
        the file content to markdown, and outputs the html to either the provided
        filename or stdout in the same encoding as the source file.
    
        **Note:** This is the only place that decoding and encoding takes place
        in Python-Markdown.
    
        Keyword arguments:
    
        * input: Name of source text file.
        * output: Name of output file. Writes to stdout if `None`.
        * extensions: A list of extension names (may contain config args).  
        * encoding: Encoding of input and output files. Defaults to utf-8.
        * message_threshold: Error reporting level.
        * safe_mode: Disallow raw html. One of "remove", "replace" or "escape".
    
        Returns: An HTML document as a string.
    
        """
    
        global console_hndlr
        console_hndlr.setLevel(message_threshold)
    
        message(DEBUG, "input file: %s" % input)
    
        if not encoding:
            encoding = "utf-8"
    
        input_file = codecs.open(input, mode="r", encoding=encoding)
        text = input_file.read()
        input_file.close()
    
        text = removeBOM(text, encoding)
    
        new_text = markdown(text, extensions, safe_mode = safe)
    
        if output:
            output_file = codecs.open(output, "w", encoding=encoding)
            output_file.write(new_text)
            output_file.close()
    
        else:
            sys.stdout.write(new_text.encode(encoding))
    
    def markdown(text,
                 extensions = [],
                 safe_mode = False):
        """
        Convenience wrapper function for `Markdown` class.
    
        Useful in a typical use case. Initializes an instance of the `Markdown` 
        class, loads any extensions and runs the parser on the given text. 
    
        Keyword arguments:
    
        * text: An ascii or Unicode string of Markdown formatted text.
        * extensions: A list of extension names (may contain config args).  
        * safe_mode: Disallow raw html. One of "remove", "replace" or "escape".
    
        Returns: An HTML document as a string.
    
        """
        message(DEBUG, "in markdown.markdown(), received text:\n%s" % text)
    
        extensions = [load_extension(e) for e in extensions]
    
        md = Markdown(extensions=extensions,
                      safe_mode = safe_mode)
    
        return md.convert(text)
            
    
    class Extension:
        """ Base class for extensions to subclass. """
        def __init__(self, configs = {}):
            """ 
            Create an instance of an Extention. 
            
            Keyword arguments:
    
            * configs: A dict of configuration setting used by an Extension.
            """
            self.config = configs
    
        def getConfig(self, key):
            """ Return a setting for the given key or an empty string. """
            if self.config.has_key(key):
                return self.config[key][0]
            else:
                return ""
    
        def getConfigInfo(self):
            """ Return all config settings as a list of tuples. """
            return [(key, self.config[key][1]) for key in self.config.keys()]
    
        def setConfig(self, key, value):
            """ Set a config setting for `key` with the given `value`. """
            self.config[key][0] = value
    
        def extendMarkdown(self, md, md_globals):
            """ 
            Add the various proccesors and patterns to the Markdown Instance. 
            
            This method must be overriden by every extension.
    
            Ketword arguments:
    
            * md: The Markdown instance.
    
            * md_globals: All global variables availabel in the markdown module
            namespace.
    
            """
            pass
    
    
    def load_extension(ext_name, configs = []):
        """ 
        Load extension by name, then return the module.
        
        The extension name may contain arguments as part of the string in the 
        following format:
    
            "extname(key1=value1,key2=value2)"
        
        Print an error message and exit on failure. 
        
        """
    
        # I am making the assumption that the order of config options
        # does not matter.
        configs = dict(configs)
        pos = ext_name.find("(") 
        if pos > 0:
            ext_args = ext_name[pos+1:-1]
            ext_name = ext_name[:pos]
            pairs = [x.split("=") for x in ext_args.split(",")]
            configs.update([(x.strip(), y.strip()) for (x, y) in pairs])
    
        ext_module = 'markdown_extensions'
        module_name = '.'.join([ext_module, ext_name])
        extension_module_name = '_'.join(['mdx', ext_name])
    
        try:
                module = __import__(module_name, {}, {}, [ext_module])
        except ImportError:
            try:
                module = __import__(extension_module_name)
            except:
                message(WARN,
                    "Failed loading extension '%s' from '%s' or '%s' "
                    "- continuing without."
                    % (ext_name, module_name, extension_module_name) )
                # Return a dummy (do nothing) Extension as silent failure
                return Extension(configs={})
    
        return module.makeExtension(configs.items())    
    
    
    OPTPARSE_WARNING = """
    Python 2.3 or higher required for advanced command line options.
    For lower versions of Python use:
    
          %s INPUT_FILE > OUTPUT_FILE
        
    """ % EXECUTABLE_NAME_FOR_USAGE
    
    def parse_options():
        """
        Define and parse `optparse` options for command-line usage.
        """
    
        try:
            optparse = __import__("optparse")
        except:
            if len(sys.argv) == 2:
                return {'input': sys.argv[1],
                        'output': None,
                        'message_threshold': CRITICAL,
                        'safe': False,
                        'extensions': [],
                        'encoding': None }
    
            else:
                print OPTPARSE_WARNING
                return None
    
        parser = optparse.OptionParser(usage="%prog INPUTFILE [options]")
    
        parser.add_option("-f", "--file", dest="filename",
                          help="write output to OUTPUT_FILE",
                          metavar="OUTPUT_FILE")
        parser.add_option("-e", "--encoding", dest="encoding",
                          help="encoding for input and output files",)
        parser.add_option("-q", "--quiet", default = CRITICAL,
                          action="store_const", const=60, dest="verbose",
                          help="suppress all messages")
        parser.add_option("-v", "--verbose",
                          action="store_const", const=INFO, dest="verbose",
                          help="print info messages")
        parser.add_option("-s", "--safe", dest="safe", default=False,
                          metavar="SAFE_MODE",
                          help="safe mode ('replace', 'remove' or 'escape'  user's HTML tag)")
        
        parser.add_option("--noisy",
                          action="store_const", const=DEBUG, dest="verbose",
                          help="print debug messages")
        parser.add_option("-x", "--extension", action="append", dest="extensions",
                          help = "load extension EXTENSION", metavar="EXTENSION")
    
        (options, args) = parser.parse_args()
    
        if not len(args) == 1:
            parser.print_help()
            return None
        else:
            input_file = args[0]
    
        if not options.extensions:
            options.extensions = []
    
        return {'input': input_file,
                'output': options.filename,
                'message_threshold': options.verbose,
                'safe': options.safe,
                'extensions': options.extensions,
                'encoding': options.encoding }
    
    def main():
        """ Run Markdown from the command line. """
    
        options = parse_options()
    
        if not options:
            sys.exit(0)
        
        markdownFromFile(**options)
    
    if __name__ == '__main__':
        main()