dot directive for reStructuredText, with this you can write ..dot:: things

dot.py

"""
dot directive (require graphviz)
"""

from docutils import nodes
from docutils.parsers.rst import directives, Directive

import subprocess as sp

nthUnnamed = 0
class Dot(Directive):
    required_arguments = 0
    optional_arguments = 1
    has_content = True
    final_argument_whitespace = True

    '''dot image generator'''
    def run(self):
        self.assert_has_content()
        global nthUnnamed
        try:
            filename = self.arguments[0]
        except:
            filename = ('dot%d.png' % nthUnnamed)
            nthUnnamed += 1
        content = '\n'.join(self.content)
        filetype = filename[filename.rfind('.')+1:]
        args = ['dot', '-o'+filename, '-T'+filetype]
        dot = sp.Popen(args, 0, None, sp.PIPE)
        dot.stdin.write( content )
        dot.stdin.close()
        ret = dot.wait()
        if ret:
            return [nodes.error('some error occured')]
        else:
            return [nodes.raw('', '<img src="%s" alt="%s"/>'%(filename, filename), format='html')]

Slight modification to use inline images thus avoiding files created on disk.

"""
dot directive (require graphviz)
"""

import base64
from docutils import nodes
from docutils.parsers.rst import directives, Directive

import subprocess as sp

nthUnnamed = 0
class Dot(Directive):
    required_arguments = 0
    optional_arguments = 1
    has_content = True
    final_argument_whitespace = True

    '''dot image generator'''
    def run(self):
        self.assert_has_content()
        global nthUnnamed
        try:
            filename = self.arguments[0]
        except:
            filename = ('dot%d.png' % nthUnnamed)
            nthUnnamed += 1
        content = '\n'.join(self.content)

        return self.render(content, filename)

    def render(self, content, filename):
        filetype = filename[filename.rfind('.')+1:]
        args = ['dot', '-T'+filetype]
        try:
                dot = sp.Popen(args, stdin=sp.PIPE, stderr=sp.PIPE,stdout=sp.PIPE)
                dot.stdin.write( content )
                dot.stdin.close()

                output = ''
                while True:
                    b = dot.stdout.read()
                    if b :
                        output = output + str(b)
                    else :
                        break

                err = ''
                while True:
                    b= dot.stderr.readline()
                    if not b :
                        break
                    err = err + b

                ret = dot.wait()

                encoded = base64.b64encode(output)

                html = '<img src="data:image/%s;base64,%s" >' % (filetype, encoded)

        except Exception as e:
                err = str(e ) + ' : ' +  str(args)

        if html:
                return [nodes.raw('', html, format='html')]
        else:
                return [nodes.raw('', '<p>Error : ' + err + '</p><pre>' + content + '</pre>', format='html')]

Nice work. Any idea how I can make this run for pdf files?

For python3 (so you can use with OmniMarkup for example):

"""
dot directive (require graphviz)
"""

import base64
from docutils import nodes
from docutils.parsers.rst import directives, Directive

import subprocess as sp

nthUnnamed = 0
class Dot(Directive):
    required_arguments = 0
    optional_arguments = 1
    has_content = True
    final_argument_whitespace = True

    '''dot image generator'''
    def run(self):
        self.assert_has_content()
        global nthUnnamed
        try:
            filename = self.arguments[0]
        except:
            filename = ('dot%d.png' % nthUnnamed)
            nthUnnamed += 1
        content = '\n'.join(self.content)

        return self.render(content, filename)

    def render(self, content, filename):
        filetype = filename[filename.rfind('.')+1:]
        args = ['dot', '-T'+filetype]
        html = None

        dot = sp.Popen(args, stdin=sp.PIPE, stderr=sp.PIPE,stdout=sp.PIPE)
        output = dot.communicate( content.encode('utf-8'))

        encoded = base64.b64encode(output[0]).decode('utf-8')

        html = '<img src="data:image/%s;base64,%s" >' % (filetype, encoded)

        if html:
                return [nodes.raw('', html, format='html')]
        else:
                return [nodes.raw('', '<p>Error : ' + err + '</p><pre>' + content + '</pre>', format='html')]