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Python Markdown
A Python implementation of John Gruber's Markdown.
Started by Manfred Stienstra (
Maintained for a few years by Yuri Takhteyev (
Currently maintained by Waylan Limberg (,
Dmitry Shachnev ( and Isaac Muse (
Copyright 2007-2018 The Python Markdown Project (v. 1.7 and later)
Copyright 2004, 2005, 2006 Yuri Takhteyev (v. 0.2-1.6b)
Copyright 2004 Manfred Stienstra (the original version)
License: BSD (see for details).
import re
import xml.etree.ElementTree as etree
from . import util
from . import inlinepatterns
def build_treeprocessors(md, **kwargs):
""" Build the default treeprocessors for Markdown. """
treeprocessors = util.Registry()
treeprocessors.register(InlineProcessor(md), 'inline', 20)
treeprocessors.register(PrettifyTreeprocessor(md), 'prettify', 10)
treeprocessors.register(UnescapeTreeprocessor(md), 'unescape', 0)
return treeprocessors
def isString(s):
""" Check if it's string """
if not isinstance(s, util.AtomicString):
return isinstance(s, str)
return False
class Treeprocessor(util.Processor):
Treeprocessors are run on the ElementTree object before serialization.
Each Treeprocessor implements a "run" method that takes a pointer to an
ElementTree, modifies it as necessary and returns an ElementTree
Treeprocessors must extend markdown.Treeprocessor.
def run(self, root):
Subclasses of Treeprocessor should implement a `run` method, which
takes a root ElementTree. This method can return another ElementTree
object, and the existing root ElementTree will be replaced, or it can
modify the current tree and return None.
pass # pragma: no cover
class InlineProcessor(Treeprocessor):
A Treeprocessor that traverses a tree, applying inline patterns.
def __init__(self, md):
self.__placeholder_prefix = util.INLINE_PLACEHOLDER_PREFIX
self.__placeholder_suffix = util.ETX
self.__placeholder_length = 4 + len(self.__placeholder_prefix) \
+ len(self.__placeholder_suffix)
self.__placeholder_re = util.INLINE_PLACEHOLDER_RE = md
self.inlinePatterns = md.inlinePatterns
self.ancestors = []
def __makePlaceholder(self, type):
""" Generate a placeholder """
id = "%04d" % len(self.stashed_nodes)
hash = util.INLINE_PLACEHOLDER % id
return hash, id
def __findPlaceholder(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 the found placeholder.
m =, index)
if m:
return, m.end()
return None, index + 1
def __stashNode(self, node, type):
""" Add node to stash """
placeholder, id = self.__makePlaceholder(type)
self.stashed_nodes[id] = node
return placeholder
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 not isinstance(data, util.AtomicString):
startIndex = 0
count = len(self.inlinePatterns)
while patternIndex < count:
data, matched, startIndex = self.__applyPattern(
self.inlinePatterns[patternIndex], data, patternIndex, startIndex
if not matched:
patternIndex += 1
return data
def __processElementText(self, node, subnode, isText=True):
Process placeholders in Element.text or Element.tail
of Elements popped from self.stashed_nodes.
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
text = subnode.tail
subnode.tail = None
childResult = self.__processPlaceholders(text, subnode, isText)
if not isText and node is not subnode:
pos = list(node).index(subnode) + 1
pos = 0
for newChild in childResult:
node.insert(pos, newChild[0])
def __processPlaceholders(self, data, parent, isText=True):
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][0].tail:
result[-1][0].tail += text
result[-1][0].tail = text
elif not isText:
if parent.tail:
parent.tail += text
parent.tail = text
if parent.text:
parent.text += text
parent.text = text
result = []
strartIndex = 0
while data:
index = data.find(self.__placeholder_prefix, strartIndex)
if index != -1:
id, phEndIndex = self.__findPlaceholder(data, index)
if id in self.stashed_nodes:
node = self.stashed_nodes.get(id)
if index > 0:
text = data[strartIndex:index]
if not isString(node): # it's Element
for child in [node] + list(node):
if child.tail:
if child.tail.strip():
node, child, False
if child.text:
if child.text.strip():
self.__processElementText(child, child)
else: # it's just a string
strartIndex = phEndIndex
strartIndex = phEndIndex
result.append((node, self.ancestors[:]))
else: # wrong placeholder
end = index + len(self.__placeholder_prefix)
strartIndex = end
text = data[strartIndex:]
if isinstance(data, util.AtomicString):
# We don't want to loose the AtomicString
text = util.AtomicString(text)
data = ""
return result
def __applyPattern(self, pattern, data, patternIndex, startIndex=0):
Check if the line fits the pattern, create the necessary
elements, add it to stashed_nodes.
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 start searching
Returns: String with placeholders instead of ElementTree elements.
new_style = isinstance(pattern, inlinepatterns.InlineProcessor)
for exclude in pattern.ANCESTOR_EXCLUDES:
if exclude.lower() in self.ancestors:
return data, False, 0
if new_style:
match = None
# Since handleMatch may reject our first match,
# we iterate over the buffer looking for matches
# until we can't find any more.
for match in pattern.getCompiledRegExp().finditer(data, startIndex):
node, start, end = pattern.handleMatch(match, data)
if start is None or end is None:
startIndex += match.end(0)
match = None
else: # pragma: no cover
match = pattern.getCompiledRegExp().match(data[startIndex:])
leftData = data[:startIndex]
if not match:
return data, False, 0
if not new_style: # pragma: no cover
node = pattern.handleMatch(match)
start = match.start(0)
end = match.end(0)
if node is None:
return data, True, end
if not isString(node):
if not isinstance(node.text, util.AtomicString):
# We need to process current node too
for child in [node] + list(node):
if not isString(node):
if child.text:
child.text = self.__handleInline(
child.text, patternIndex + 1
if child.tail:
child.tail = self.__handleInline(
child.tail, patternIndex
placeholder = self.__stashNode(node, pattern.type())
if new_style:
return "{}{}{}".format(data[:start],
placeholder, data[end:]), True, 0
else: # pragma: no cover
return "{}{}{}{}".format(leftData,,
placeholder, match.groups()[-1]), True, 0
def __build_ancestors(self, parent, parents):
"""Build the ancestor list."""
ancestors = []
while parent is not None:
if parent is not None:
parent = self.parent_map.get(parent)
def run(self, tree, ancestors=None):
"""Apply inline patterns to a parsed Markdown tree.
Iterate over ElementTree, find elements with inline tag, apply inline
patterns and append newly created Elements to tree. If you don't
want to process your data with inline patterns, instead of normal
string, use subclass AtomicString:
node.text = markdown.AtomicString("This will not be processed.")
* tree: ElementTree object, representing Markdown tree.
* ancestors: List of parent tag names that precede the tree node (if needed).
Returns: ElementTree object with applied inline patterns.
self.stashed_nodes = {}
# Ensure a valid parent list, but copy passed in lists
# to ensure we don't have the user accidentally change it on us.
tree_parents = [] if ancestors is None else ancestors[:]
self.parent_map = {c: p for p in tree.iter() for c in p}
stack = [(tree, tree_parents)]
while stack:
currElement, parents = stack.pop()
self.ancestors = parents
self.__build_ancestors(currElement, self.ancestors)
insertQueue = []
for child in currElement:
if child.text and not isinstance(
child.text, util.AtomicString
text = child.text
child.text = None
lst = self.__processPlaceholders(
self.__handleInline(text), child
for item in lst:
self.parent_map[item[0]] = child
stack += lst
insertQueue.append((child, lst))
if child.tail:
tail = self.__handleInline(child.tail)
dumby = etree.Element('d')
child.tail = None
tailResult = self.__processPlaceholders(tail, dumby, False)
if dumby.tail:
child.tail = dumby.tail
pos = list(currElement).index(child) + 1
for newChild in tailResult:
self.parent_map[newChild[0]] = currElement
currElement.insert(pos, newChild[0])
if len(child):
self.parent_map[child] = currElement
stack.append((child, self.ancestors[:]))
for element, lst in insertQueue:
for i, obj in enumerate(lst):
newChild = obj[0]
element.insert(i, newChild)
return tree
class PrettifyTreeprocessor(Treeprocessor):
""" Add linebreaks to the html document. """
def _prettifyETree(self, elem):
""" Recursively add linebreaks to ElementTree children. """
i = "\n"
if and elem.tag not in ['code', 'pre']:
if (not elem.text or not elem.text.strip()) \
and len(elem) and[0].tag):
elem.text = i
for e in elem:
if not elem.tail or not elem.tail.strip():
elem.tail = i
def run(self, root):
""" Add linebreaks to ElementTree root object. """
# Do <br />'s separately as they are often in the middle of
# inline content and missed by _prettifyETree.
brs = root.iter('br')
for br in brs:
if not br.tail or not br.tail.strip():
br.tail = '\n'
br.tail = '\n%s' % br.tail
# Clean up extra empty lines at end of code blocks.
pres = root.iter('pre')
for pre in pres:
if len(pre) and pre[0].tag == 'code':
code = pre[0]
# Only prettify code containing text only
if not len(code) and code.text is not None:
code.text = util.AtomicString(code.text.rstrip() + '\n')
class UnescapeTreeprocessor(Treeprocessor):
""" Restore escaped chars """
RE = re.compile(r'{}(\d+){}'.format(util.STX, util.ETX))
def _unescape(self, m):
return chr(int(
def unescape(self, text):
return self.RE.sub(self._unescape, text)
def run(self, root):
""" Loop over all elements and unescape all text. """
for elem in root.iter():
# Unescape text content
if elem.text and not elem.tag == 'code':
elem.text = self.unescape(elem.text)
# Unescape tail content
if elem.tail:
elem.tail = self.unescape(elem.tail)
# Unescape attribute values
for key, value in elem.items():
elem.set(key, self.unescape(value))