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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 codecs
import sys
import logging
import importlib
from . import util
from .preprocessors import build_preprocessors
from .blockprocessors import build_block_parser
from .treeprocessors import build_treeprocessors
from .inlinepatterns import build_inlinepatterns
from .postprocessors import build_postprocessors
from .extensions import Extension
from .serializers import to_html_string, to_xhtml_string
__all__ = ['Markdown', 'markdown', 'markdownFromFile']
logger = logging.getLogger('MARKDOWN')
class Markdown:
"""Convert Markdown to HTML."""
doc_tag = "div" # Element used to wrap document - later removed
output_formats = {
'html': to_html_string,
'xhtml': to_xhtml_string,
def __init__(self, **kwargs):
Creates a new Markdown instance.
Keyword arguments:
* extensions: A list of extensions.
If an item is an instance of a subclass of `markdown.extension.Extension`, the instance will be used
as-is. If an item is of type string, first an entry point will be loaded. If that fails, the string is
assumed to use Python dot notation (``) to load a markdown.Extension subclass. If
no class is specified, then a `makeExtension` function is called within the specified module.
* extension_configs: Configuration settings for extensions.
* output_format: Format of output. Supported formats are:
* "xhtml": Outputs XHTML style tags. Default.
* "html": Outputs HTML style tags.
* tab_length: Length of tabs in the source. Default: 4
self.tab_length = kwargs.get('tab_length', 4)
self.ESCAPED_CHARS = ['\\', '`', '*', '_', '{', '}', '[', ']',
'(', ')', '>', '#', '+', '-', '.', '!']
self.block_level_elements = [
# Elements which are invalid to wrap in a `<p>` tag.
# See
'address', 'article', 'aside', 'blockquote', 'details', 'div', 'dl',
'fieldset', 'figcaption', 'figure', 'footer', 'form', 'h1', 'h2', 'h3',
'h4', 'h5', 'h6', 'header', 'hgroup', 'hr', 'main', 'menu', 'nav', 'ol',
'p', 'pre', 'section', 'table', 'ul',
# Other elements which Markdown should not be mucking up the contents of.
'canvas', 'colgroup', 'dd', 'body', 'dt', 'group', 'iframe', 'li', 'legend',
'math', 'map', 'noscript', 'output', 'object', 'option', 'progress', 'script',
'style', 'summary', 'tbody', 'td', 'textarea', 'tfoot', 'th', 'thead', 'tr', 'video'
self.registeredExtensions = []
self.docType = ""
self.stripTopLevelTags = True
self.references = {}
self.htmlStash = util.HtmlStash()
self.registerExtensions(extensions=kwargs.get('extensions', []),
configs=kwargs.get('extension_configs', {}))
self.set_output_format(kwargs.get('output_format', 'xhtml'))
def build_parser(self):
""" Build the parser from the various parts. """
self.preprocessors = build_preprocessors(self)
self.parser = build_block_parser(self)
self.inlinePatterns = build_inlinepatterns(self)
self.treeprocessors = build_treeprocessors(self)
self.postprocessors = build_postprocessors(self)
return self
def registerExtensions(self, extensions, configs):
Register extensions with this instance of Markdown.
Keyword arguments:
* extensions: A list of extensions, which can either
be strings or objects.
* configs: A dictionary mapping extension names to config options.
for ext in extensions:
if isinstance(ext, str):
ext = self.build_extension(ext, configs.get(ext, {}))
if isinstance(ext, Extension):
'Successfully loaded extension "%s.%s".'
% (ext.__class__.__module__, ext.__class__.__name__)
elif ext is not None:
raise TypeError(
'Extension "{}.{}" must be of type: "{}.{}"'.format(
ext.__class__.__module__, ext.__class__.__name__,
Extension.__module__, Extension.__name__
return self
def build_extension(self, ext_name, configs):
Build extension from a string name, then return an instance.
First attempt to load an entry point. The string name must be registered as an entry point in the
`markdown.extensions` group which points to a subclass of the `markdown.extensions.Extension` class.
If multiple distributions have registered the same name, the first one found is returned.
If no entry point is found, assume dot notation (``). Load the specified class and
return an instance. If no class is specified, import the module and call a `makeExtension` function and return
the Extension instance returned by that function.
configs = dict(configs)
entry_points = [ep for ep in util.get_installed_extensions() if == ext_name]
if entry_points:
ext = entry_points[0].load()
return ext(**configs)
# Get class name (if provided): ``
ext_name, class_name = ext_name.split(':', 1) if ':' in ext_name else (ext_name, '')
module = importlib.import_module(ext_name)
'Successfully imported extension module "%s".' % ext_name
except ImportError as e:
message = 'Failed loading extension "%s".' % ext_name
e.args = (message,) + e.args[1:]
if class_name:
# Load given class name from module.
return getattr(module, class_name)(**configs)
# Expect makeExtension() function to return a class.
return module.makeExtension(**configs)
except AttributeError as e:
message = e.args[0]
message = "Failed to initiate extension " \
"'%s': %s" % (ext_name, message)
e.args = (message,) + e.args[1:]
def registerExtension(self, extension):
""" This gets called by the extension """
return self
def reset(self):
Resets all state variables so that we can start with a new text.
for extension in self.registeredExtensions:
if hasattr(extension, 'reset'):
return self
def set_output_format(self, format):
""" Set the output format for the class instance. """
self.output_format = format.lower().rstrip('145') # ignore num
self.serializer = self.output_formats[self.output_format]
except KeyError as e:
valid_formats = list(self.output_formats.keys())
message = 'Invalid Output Format: "%s". Use one of %s.' \
% (self.output_format,
'"' + '", "'.join(valid_formats) + '"')
e.args = (message,) + e.args[1:]
return self
def is_block_level(self, tag):
"""Check if the tag is a block level HTML tag."""
if isinstance(tag, str):
return tag.lower().rstrip('/') in self.block_level_elements
# Some ElementTree tags are not strings, so return False.
return False
def convert(self, source):
Convert markdown to serialized XHTML or HTML.
Keyword arguments:
* source: Source text as a Unicode string.
Markdown processing takes place in five steps:
1. A bunch of "preprocessors" munge the input text.
2. BlockParser() parses the high-level structural elements of the
pre-processed text into an ElementTree.
3. A bunch of "treeprocessors" are run against the ElementTree. One
such treeprocessor runs InlinePatterns against the ElementTree,
detecting inline markup.
4. Some post-processors are run against the text after the ElementTree
has been serialized into text.
5. The output is written to a string.
# Fixup the source text
if not source.strip():
return '' # a blank unicode string
source = str(source)
except UnicodeDecodeError as e: # pragma: no cover
# Customise error message while maintaining original trackback
e.reason += '. -- Note: Markdown only accepts unicode input!'
# Split into lines and run the line preprocessors.
self.lines = source.split("\n")
for prep in self.preprocessors:
self.lines =
# Parse the high-level elements.
root = self.parser.parseDocument(self.lines).getroot()
# Run the tree-processors
for treeprocessor in self.treeprocessors:
newRoot =
if newRoot is not None:
root = newRoot
# Serialize _properly_. Strip top-level tags.
output = self.serializer(root)
if self.stripTopLevelTags:
start = output.index(
'<%s>' % self.doc_tag) + len(self.doc_tag) + 2
end = output.rindex('</%s>' % self.doc_tag)
output = output[start:end].strip()
except ValueError as e: # pragma: no cover
if output.strip().endswith('<%s />' % self.doc_tag):
# We have an empty document
output = ''
# We have a serious problem
raise ValueError('Markdown failed to strip top-level '
'tags. Document=%r' % output.strip()) from e
# Run the text post-processors
for pp in self.postprocessors:
output =
return output.strip()
def convertFile(self, input=None, output=None, encoding=None):
"""Converts a markdown file and returns the HTML as a unicode string.
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 stream or the file with provided name, using the same
encoding as the source file. The 'xmlcharrefreplace' error handler is
used when encoding the output.
**Note:** This is the only place that decoding and encoding of unicode
takes place in Python-Markdown. (All other code is unicode-in /
Keyword arguments:
* input: File object or path. Reads from stdin if `None`.
* output: File object or path. Writes to stdout if `None`.
* encoding: Encoding of input and output files. Defaults to utf-8.
encoding = encoding or "utf-8"
# Read the source
if input:
if isinstance(input, str):
input_file =, mode="r", encoding=encoding)
input_file = codecs.getreader(encoding)(input)
text =
text =
if not isinstance(text, str): # pragma: no cover
text = text.decode(encoding)
text = text.lstrip('\ufeff') # remove the byte-order mark
# Convert
html = self.convert(text)
# Write to file or stdout
if output:
if isinstance(output, str):
output_file =, "w",
writer = codecs.getwriter(encoding)
output_file = writer(output, errors="xmlcharrefreplace")
# Don't close here. User may want to write more.
# Encode manually and write bytes to stdout.
html = html.encode(encoding, "xmlcharrefreplace")
# Write bytes directly to buffer (Python 3).
except AttributeError: # pragma: no cover
# Probably Python 2, which works with bytes by default.
return self
Those are the two functions we really mean to export: markdown() and
def markdown(text, **kwargs):
"""Convert a markdown string to HTML and return HTML as a unicode string.
This is a shortcut function for `Markdown` class to cover the most
basic use case. It initializes an instance of Markdown, loads the
necessary extensions and runs the parser on the given text.
Keyword arguments:
* text: Markdown formatted text as Unicode or ASCII string.
* Any arguments accepted by the Markdown class.
Returns: An HTML document as a string.
md = Markdown(**kwargs)
return md.convert(text)
def markdownFromFile(**kwargs):
"""Read markdown code from a file and write it to a file or a stream.
This is a shortcut function which initializes an instance of Markdown,
and calls the convertFile method rather than convert.
Keyword arguments:
* input: a file name or readable object.
* output: a file name or writable object.
* encoding: Encoding of input and output.
* Any arguments accepted by the Markdown class.
md = Markdown(**kwargs)
md.convertFile(kwargs.get('input', None),
kwargs.get('output', None),
kwargs.get('encoding', None))