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This recipe provides a couple of cross-platform utility functions, 'open' and 'mailto', for opening files and URLs in the registered default application and for sending e-mails using the user's preferred composer. The python standard library already provides the os.startfie function that allows the user to open a generic file in the associated application but it only works on Windows. The 'webbrowser' module is cross-platform but only handles a specific kind of application, the web browser, and it is useless if one wants to open e.g. a source code python file in the user's preferred text editor. The 'open' function simply opens the file or URL passed as parameter in the system registered application. The 'mailto' function starts the user's preferred e-mail composer and pre-fills the 'to', 'cc','bcc' and 'subject' headers if corresponding parameters are provided. It also handles parameters for the message body and for attachments.

Python, 338 lines
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#!/usr/bin/env python

'''Utilities for opening files or URLs in the registered default application
and for sending e-mail using the user's preferred composer.

'''

__version__ = '1.1'
__all__ = ['open', 'mailto']

import os
import sys
import webbrowser
import subprocess

from email.Utils import encode_rfc2231

_controllers = {}
_open = None


class BaseController(object):
    '''Base class for open program controllers.'''

    def __init__(self, name):
        self.name = name

    def open(self, filename):
        raise NotImplementedError


class Controller(BaseController):
    '''Controller for a generic open program.'''

    def __init__(self, *args):
        super(Controller, self).__init__(os.path.basename(args[0]))
        self.args = list(args)

    def _invoke(self, cmdline):
        if sys.platform[:3] == 'win':
            closefds = False
            startupinfo = subprocess.STARTUPINFO()
            startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
        else:
            closefds = True
            startupinfo = None

        if (os.environ.get('DISPLAY') or sys.platform[:3] == 'win' or
                                                    sys.platform == 'darwin'):
            inout = file(os.devnull, 'r+')
        else:
            # for TTY programs, we need stdin/out
            inout = None

        # if possible, put the child precess in separate process group,
        # so keyboard interrupts don't affect child precess as well as
        # Python
        setsid = getattr(os, 'setsid', None)
        if not setsid:
            setsid = getattr(os, 'setpgrp', None)

        pipe = subprocess.Popen(cmdline, stdin=inout, stdout=inout,
                                stderr=inout, close_fds=closefds,
                                preexec_fn=setsid, startupinfo=startupinfo)

        # It is assumed that this kind of tools (gnome-open, kfmclient,
        # exo-open, xdg-open and open for OSX) immediately exit after lauching
        # the specific application
        returncode = pipe.wait()
        if hasattr(self, 'fixreturncode'):
            returncode = self.fixreturncode(returncode)
        return not returncode

    def open(self, filename):
        if isinstance(filename, basestring):
            cmdline = self.args + [filename]
        else:
            # assume it is a sequence
            cmdline = self.args + filename
        try:
            return self._invoke(cmdline)
        except OSError:
            return False


# Platform support for Windows
if sys.platform[:3] == 'win':

    class Start(BaseController):
        '''Controller for the win32 start progam through os.startfile.'''

        def open(self, filename):
            try:
                os.startfile(filename)
            except WindowsError:
                # [Error 22] No application is associated with the specified
                # file for this operation: '<URL>'
                return False
            else:
                return True

    _controllers['windows-default'] = Start('start')
    _open = _controllers['windows-default'].open


# Platform support for MacOS
elif sys.platform == 'darwin':
    _controllers['open']= Controller('open')
    _open = _controllers['open'].open


# Platform support for Unix
else:

    import commands

    # @WARNING: use the private API of the webbrowser module
    from webbrowser import _iscommand

    class KfmClient(Controller):
        '''Controller for the KDE kfmclient program.'''

        def __init__(self, kfmclient='kfmclient'):
            super(KfmClient, self).__init__(kfmclient, 'exec')
            self.kde_version = self.detect_kde_version()

        def detect_kde_version(self):
            kde_version = None
            try:
                info = commands.getoutput('kde-config --version')

                for line in info.splitlines():
                    if line.startswith('KDE'):
                        kde_version = line.split(':')[-1].strip()
                        break
            except (OSError, RuntimeError):
                pass

            return kde_version

        def fixreturncode(self, returncode):
            if returncode is not None and self.kde_version > '3.5.4':
                return returncode
            else:
                return os.EX_OK

    def detect_desktop_environment():
        '''Checks for known desktop environments

        Return the desktop environments name, lowercase (kde, gnome, xfce)
        or "generic"

        '''

        desktop_environment = 'generic'

        if os.environ.get('KDE_FULL_SESSION') == 'true':
            desktop_environment = 'kde'
        elif os.environ.get('GNOME_DESKTOP_SESSION_ID'):
            desktop_environment = 'gnome'
        else:
            try:
                info = commands.getoutput('xprop -root _DT_SAVE_MODE')
                if ' = "xfce4"' in info:
                    desktop_environment = 'xfce'
            except (OSError, RuntimeError):
                pass

        return desktop_environment


    def register_X_controllers():
        if _iscommand('kfmclient'):
            _controllers['kde-open'] = KfmClient()

        for command in ('gnome-open', 'exo-open', 'xdg-open'):
            if _iscommand(command):
                _controllers[command] = Controller(command)

    def get():
        controllers_map = {
            'gnome': 'gnome-open',
            'kde': 'kde-open',
            'xfce': 'exo-open',
        }

        desktop_environment = detect_desktop_environment()

        try:
            controller_name = controllers_map[desktop_environment]
            return _controllers[controller_name].open

        except KeyError:
            if _controllers.has_key('xdg-open'):
                return _controllers['xdg-open'].open
            else:
                return webbrowser.open


    if os.environ.get("DISPLAY"):
        register_X_controllers()
    _open = get()


def open(filename):
    '''Open a file or an URL in the registered default application.'''

    return _open(filename)


def _fix_addersses(**kwargs):
    for headername in ('address', 'to', 'cc', 'bcc'):
        try:
            headervalue = kwargs[headername]
            if not headervalue:
                del kwargs[headername]
                continue
            elif not isinstance(headervalue, basestring):
                # assume it is a sequence
                headervalue = ','.join(headervalue)

        except KeyError:
            pass
        except TypeError:
            raise TypeError('string or sequence expected for "%s", '
                            '%s found' % (headername,
                                          type(headervalue).__name__))
        else:
            translation_map = {'%': '%25', '&': '%26', '?': '%3F'}
            for char, replacement in translation_map.items():
                headervalue = headervalue.replace(char, replacement)
            kwargs[headername] = headervalue

    return kwargs


def mailto_format(**kwargs):
    # @TODO: implement utf8 option

    kwargs = _fix_addersses(**kwargs)
    parts = []
    for headername in ('to', 'cc', 'bcc', 'subject', 'body', 'attach'):
        if kwargs.has_key(headername):
            headervalue = kwargs[headername]
            if not headervalue:
                continue
            if headername in ('address', 'to', 'cc', 'bcc'):
                parts.append('%s=%s' % (headername, headervalue))
            else:
                headervalue = encode_rfc2231(headervalue) # @TODO: check
                parts.append('%s=%s' % (headername, headervalue))

    mailto_string = 'mailto:%s' % kwargs.get('address', '')
    if parts:
        mailto_string = '%s?%s' % (mailto_string, '&'.join(parts))

    return mailto_string


def mailto(address, to=None, cc=None, bcc=None, subject=None, body=None,
           attach=None):
    '''Send an e-mail using the user's preferred composer.

    Open the user's preferred e-mail composer in order to send a mail to
    address(es) that must follow the syntax of RFC822. Multiple addresses
    may be provided (for address, cc and bcc parameters) as separate
    arguments.

    All parameters provided are used to prefill corresponding fields in
    the user's e-mail composer. The user will have the opportunity to
    change any of this information before actually sending the e-mail.

    address - specify the destination recipient
    cc      - specify a recipient to be copied on the e-mail
    bcc     - specify a recipient to be blindly copied on the e-mail
    subject - specify a subject for the e-mail
    body    - specify a body for the e-mail. Since the user will be able
              to make changes before actually sending the e-mail, this
              can be used to provide the user with a template for the
              e-mail text may contain linebreaks
    attach  - specify an attachment for the e-mail. file must point to
              an existing file

    '''

    mailto_string = mailto_format(**locals())
    return open(mailto_string)


if __name__ == '__main__':
    from optparse import OptionParser

    version = '%%prog %s' % __version__
    usage = (
        '\n\n%prog FILENAME [FILENAME(s)] -- for opening files'
        '\n\n%prog -m [OPTIONS] ADDRESS [ADDRESS(es)] -- for sending e-mails'
    )

    parser = OptionParser(usage=usage, version=version, description=__doc__)
    parser.add_option('-m', '--mailto', dest='mailto_mode', default=False,
                      action='store_true', help='set mailto mode. '
                      'If not set any other option is ignored')
    parser.add_option('--cc', dest='cc', help='specify a recipient to be '
                      'copied on the e-mail')
    parser.add_option('--bcc', dest='bcc', help='specify a recipient to be '
                      'blindly copied on the e-mail')
    parser.add_option('--subject', dest='subject',
                      help='specify a subject for the e-mail')
    parser.add_option('--body', dest='body', help='specify a body for the '
                      'e-mail. Since the user will be able to make changes '
                      'before actually sending the e-mail, this can be used '
                      'to provide the user with a template for the e-mail '
                      'text may contain linebreaks')
    parser.add_option('--attach', dest='attach', help='specify an attachment '
                      'for the e-mail. file must point to an existing file')

    (options, args) = parser.parse_args()

    if not args:
        parser.print_usage()
        parser.exit(1)

    if options.mailto_mode:
        if not mailto(args, None, options.cc, options.bcc, options.subject,
                      options.body, options.attach):
            sys.exit('Unable to open the e-mail client')
    else:
        for name in ('cc', 'bcc', 'subject', 'body', 'attach'):
            if getattr(options, name):
                parser.error('The "cc", "bcc", "subject", "body" and "attach" '
                             'options are only accepten in mailto mode')
        success = False
        for arg in args:
            if not open(arg):
                print 'Unable to open "%s"' % arg
            else:
                success = True
        sys.exit(success)

The proposed implementation of the 'open' function relies on platform specific system tools that actually act the task: 'start' for win32, 'open' for OSX and gnome-open, kfmclient and exo-open respectively for the GNOME, KDE and XFCE desktop environment. As a fallback solution xdg-open (if available) and webbrowser.open are used. The 'open' function handles the platform specific matters and provides a simple and standard interface. The function that detects the desktop environment is a re-implementation in python of the 'detectDE' function from the xdg-tools (http://portland.freedesktop.org) while in general the xopen module setup follows the webbrowser module's one. The 'mailto' function formats a mailto-uri (as defined in RFC2368) and pass it to the 'open' function that actually opens the user's preferred e-mail client.

3 comments

Andrzej Kluge 13 years, 2 months ago  # | flag

Very useful.

Under windows I have had to make though this little change in the line 102, in order to import module without errors:

 _controllers['windows-default'] = Start('windows-default')

Under GNOME works perfect, thanks!

Antonio Valentino (author) 13 years, 2 months ago  # | flag

Thanks Andrzei. Fix uploaded.

m2j 10 years, 12 months ago  # | flag

This will give the right return code for KDE4 (line 130):

info = commands.getoutput('kfmclient --version')