[IPython-dev] ipython embedded in twisted, no threads

Stefan Rank list-ener@strank.i...
Mon Apr 16 17:23:16 CDT 2007


Hi Jörgen,

on 16.04.2007 20:16 Jörgen Stenarson said the following:
> Hi Stefan,
> 
> I'm not sure exactly what you are after (I don't use twisted myself).

I am not an expert either, I am afraid.

> But in pyreadline it is now fairly straightforward to add a new console 
> class (there are currently two: the standard win32 and one for 
> .NET/IronPython) which should implement the lowlevel keyboard and screen 
> output routines. If this is what is needed I would be happy to accept 
> patches and answer questions to help make it happen. We would probably 
> also have to work out a more sofisticated method of choosing low-level 
> console backend than what is used now.

I think what is needed for readline support in twisted is not a new 
backend but an additional frontend/API.
The 'problem' (read advantage ;-) with twisted is that it needs a 
callback interface that does not block, as it wants to do the polling 
for input events itself.

GNU readline has a callback interface that should be usable for that:
http://cnswww.cns.cwru.edu/php/chet/readline/readline.html#SEC41
(for triggering single character reading)
Would this be possible with pyreadline?

cheers,
stefan

> Stefan Rank skrev:
>> Hi,
>> [apologies if this arrives twice, posting via gmane didn't work - yet.]
>>
>> attached is an ugly first attempt at embedding IPython in a twisted
>> application without using threads.
>>
>> twisted.internet.stdio and a LineReceiver implementation are responsible
>> for getting input events.
>> I had to subclass the IPython shell and rearrange code to
>> create a non-blocking callback interface (splitting on the main,
>> blocking, raw_input call).
>>
>> It's far from perfect: readline functionality is missing (no commandline
>> navigation, history navigation, completion), and sometimes continuation
>> lines eat the input counter (In[2] ... In[4]).
>>
>> Would IPython developers be interested in patches that allow a less ugly
>> version of such a callback-friendly subclass? ;-)
>> The basic idea: refactor the main loop (InteractiveShell.interact) to::
>>
>>    setup()
>>    while ...:
>>        promptforline()
>>        raw_input
>>        handleline()
>>    teardown()
>>
>> (I think it might also be interesting for the frontend to the IPython
>> parallel computing effort, which uses twisted.)
>>
>> cheers,
>> stefan
>>
>>
>> ------------------------------------------------------------------------
>>
>> '''Testing a way to embed IPython in a twisted app without using threads.
>> (seems to work on Py25/WinXP, twisted2.5 patched with #2157, IPython0.8.0)
>>
>> twisted.internet.stdio is responsible for getting user input.
>> An implementation of the LineReceiver protocol passes received lines
>> to a custom subclass of the IPython shell (main raw_input call removed).
>>
>> No readline behaviour is available.
>> (But IPython still sets up readline and uses it for colour printing.)
>>
>> TODO:
>>     integrate readline functionality: two possibilities
>>
>>     1) Change pyreadline so that it can be called back by t.i.stdio for
>>        all things except waiting for input (i.e. completion, key bindings, ...)
>>        This would mean no further changes to IPython, which would still
>>        be using pyreadline directly.
>>        (or use a GNU readline callback interface: a t.i.stdio-alike would be
>>        polling/selecting for input, but then call readline to actually consume it.)
>>     2) Build a readline compatible interface for t.i.stdio
>>        (only the parts for setting up completeres, key bindings, ...)
>>        and make the IPython subclass use that instead of pyreadline
>>
>> As there is a lot of pasted IPython code including comments, I added
>> ##### multi-hash comments and
>> docstrings explaining the rearrangements.
>>
>> :author: strank
>> '''
>>
>> __docformat__ = "restructuredtext en"
>>
>> import sys
>> import __builtin__
>>
>> from twisted.internet import reactor, stdio
>> from twisted.protocols import basic
>> from IPython.Shell import IPShellEmbed
>> from IPython.iplib import InteractiveShell, ultraTB
>> from IPython.ipmaker import make_IPython
>>
>>
>> def main():
>>     ###### this is what we want:
>>     reactor.callWhenRunning(startTwistedStdioShell)
>>     ###### because this blocks the reactor while IPython is active:
>>     #reactor.callWhenRunning(startIPShell)
>>     reactor.run()
>>
>>
>> def startIPShell(args=None):
>>     '''The non-twisted-friendly way of embedding IPython.'''
>>     if args is None:
>>         args = []
>>     some_recognisable_local = 'WAGAWAGA' # gets exposed in Shell
>>     ipshell = IPShellEmbed(args,
>>                            banner='Standard IPython called from twisted (blocking)',
>>                            exit_msg='Leaving Interpreter, back to program.')
>>     ipshell('***Called from top level. '
>>             'Hit Ctrl-D to exit interpreter and continue program.')
>>     reactor.stop()
>>
>>
>> def startTwistedStdioShell(args=None, local_ns=None):
>>     '''On Windows, this only works with a patched twisted,
>>     because twisted.internet.stdio in twisted2.5 is unix only,
>>     see ticket #2157.
>>     '''
>>     if args is None:
>>         args = []
>>     ipshell = TwistedIPShellEmbed([],
>>                                   banner='IPython embedded in a Twisted application',
>>                                   exit_msg='Leaving Interpreter, back to program.')
>>     sp = ShellProtocol(ipshell, '***Called from top level. ', local_ns=local_ns)
>>     #sp.setRawMode()
>>     stdio.StandardIO(sp)
>>
>>
>> class TwistedIPShellEmbed(IPShellEmbed):
>>     '''Same as superclass, BUT:
>>     __init__ is duplicated, with a single difference:
>>         The actual IP shell_class is set to our own subclass.
>>     __call__ is split into two methods for setup / teardown.
>>     '''
>>
>>     def __init__(self,argv=None,banner='',exit_msg=None,rc_override=None,
>>                  user_ns=None):
>>         """Note that argv here is a string, NOT a list."""
>>         self.set_banner(banner)
>>         self.set_exit_msg(exit_msg)
>>         self.set_dummy_mode(0)
>>         # sys.displayhook is a global, we need to save the user's original
>>         # Don't rely on __displayhook__, as the user may have changed that.
>>         self.sys_displayhook_ori = sys.displayhook
>>         # save readline completer status
>>         try:
>>             #print 'Save completer',sys.ipcompleter  # dbg
>>             self.sys_ipcompleter_ori = sys.ipcompleter
>>         except:
>>             pass # not nested with IPython
>>         self.IP = make_IPython(argv,rc_override=rc_override,
>>                                embedded=True,
>>                                user_ns=user_ns,
>>                                ###### HERE IS THE DIFFERENCE  -- StefanRank
>>                                shell_class=TwistedInteractiveShell)
>>         # copy our own displayhook also
>>         self.sys_displayhook_embed = sys.displayhook
>>         # and leave the system's display hook clean
>>         sys.displayhook = self.sys_displayhook_ori
>>         # don't use the ipython crash handler so that user exceptions aren't
>>         # trapped
>>         sys.excepthook = ultraTB.FormattedTB(color_scheme = self.IP.rc.colors,
>>                                              mode = self.IP.rc.xmode,
>>                                              call_pdb = self.IP.rc.pdb)
>>         self.restore_system_completer()
>>
>>     def __call__(self,header='',local_ns=None,global_ns=None,dummy=None):
>>         # Set global subsystems (display,completions) to our values
>>         sys.displayhook = self.sys_displayhook_embed
>>         if self.IP.has_readline:
>>             self.IP.set_completer()
>>         if self.banner and header:
>>             format = '%s\n%s\n'
>>         else:
>>             format = '%s%s\n'
>>         banner =  format % (self.banner,header)
>>         # Call the embedding code with a stack depth of 1 so it can skip over
>>         # our call and get the original caller's namespaces.
>>         ###### STOP HERE, THIS embed_mainloop DOESN'T BLOCK, RETURN THE SHELL --StefanRank
>>         return self.IP.embed_mainloop(banner,local_ns,global_ns,stack_depth=1)
>>
>>     def teardown(self):
>>         ###### call the code that would have been called at the end of IP.embed_mainloop:
>>         self.IP.teardown()
>>         ###### This is the code formerly known as: the end of __call__:
>>         if self.exit_msg:
>>             print self.exit_msg
>>         # Restore global systems (display, completion)
>>         sys.displayhook = self.sys_displayhook_ori
>>         self.restore_system_completer()
>>
>>
>> class TwistedInteractiveShell(InteractiveShell):
>>     '''Subclassing to remove raw_input call and provide a callback interface.
>>     Copy-pasted and split up code of embed_mainloop, interact, raw_input.
>>     '''
>>
>>     def embed_mainloop(self,header='',local_ns=None,global_ns=None,stack_depth=0):
>>         # Get locals and globals from caller
>>         if local_ns is None or global_ns is None:
>>             call_frame = sys._getframe(stack_depth).f_back
>>             if local_ns is None:
>>                 local_ns = call_frame.f_locals
>>             if global_ns is None:
>>                 global_ns = call_frame.f_globals
>>         self.user_global_ns = global_ns
>>         local_varnames = local_ns.keys()
>>         self.user_ns.update(local_ns)
>>         if local_ns is None and global_ns is None:
>>             self.user_global_ns.update(__main__.__dict__)
>>         self.set_completer_frame()
>>         self.add_builtins()
>>         self.interact(header)
>>         return self ###### needed for later calls, interact is now non-blocking
>>
>>     def teardown(self):
>>         '''This is the code formerly known as: the end of interact and embed_mainloop.'''
>>         ##### from interact:
>>         # We are off again...
>>         __builtin__.__dict__['__IPYTHON__active'] -= 1
>>         ##### from embed_mainloop:
>>         # now, purge out the user namespace from anything we might have added
>>         # from the caller's local namespace
>>         ###### local_varnames not accessible any more,
>>         ###### should probably be saved... (TODO)
>>         ###delvar = self.user_ns.pop
>>         ###for var in local_varnames:
>>         ###    delvar(var,None)
>>         # and clean builtins we may have overridden
>>         self.clean_builtins()
>>
>>     def interact(self, banner=None):
>>         ###### HERE IT GETS HAIRY: code copied from self.interact(header)
>>         if self.exit_now:
>>             # batch run -> do not interact
>>             return ###### This does not make any sense now, since we are non-blocking
>>         cprt = 'Type "copyright", "credits" or "license" for more information.'
>>         if banner is None:
>>             self.write("Python %s on %s\n%s\n(%s)\n" %
>>                        (sys.version, sys.platform, cprt,
>>                         self.__class__.__name__))
>>         else:
>>             self.write(banner)
>>         more = 0
>>         # Mark activity in the builtins
>>         __builtin__.__dict__['__IPYTHON__active'] += 1
>>         self.promptForLine(more)
>>         return self
>>
>>     def promptForLine(self, more):
>>         '''New method. To be called before waiting for the next line.'''
>>         prompt = ''
>>         ###### THIS NEEDED TO BE UNTANGLED: originally a while loop in self.interact
>>         # exit_now is set by a call to %Exit or %Quit
>>         if not self.exit_now:
>>             if more:
>>                 prompt = self.hooks.generate_prompt(True)
>>                 if self.autoindent:
>>                     self.readline_startup_hook(self.pre_readline)
>>             else:
>>                 prompt = self.hooks.generate_prompt(False)
>>             ####### code from self.raw_input:
>>             self.set_completer()
>>             ####### write the prompt here, writing it in the LineReceiver
>>             ####### with sendLine messes up the colouring
>>             self.write(prompt)
>>         ####### raw_input BEGONE!!!
>>         ####### unfortunately all the exception handling in self.interact is also gone.
>>         ####### return and wait for a call to useLine
>>
>>     def useLine(self, line, continue_prompt=False):
>>         '''New method. To be called with a new received line.'''
>>         ####### code from self.raw_input:
>>         if line.strip():
>>             if continue_prompt:
>>                 self.input_hist_raw[-1] += '%s\n' % line
>>                 if self.has_readline: # and some config option is set?
>>                     try:
>>                         histlen = self.readline.get_current_history_length()
>>                         newhist = self.input_hist_raw[-1].rstrip()
>>                         self.readline.remove_history_item(histlen-1)
>>                         self.readline.replace_history_item(histlen-2,newhist)
>>                     except AttributeError:
>>                         pass # re{move,place}_history_item are new in 2.4.
>>             else:
>>                 self.input_hist_raw.append('%s\n' % line)
>>         try:
>>             lineout = self.prefilter(line,continue_prompt)
>>         except:
>>             # blanket except, in case a user-defined prefilter crashes, so it
>>             # can't take all of ipython with it.
>>             self.showtraceback()
>>             lineout = ''
>>         ###### CODE FROM INTERACT AGAIN:
>>         more = self.push(lineout)
>>         if (self.SyntaxTB.last_syntax_error and
>>             self.rc.autoedit_syntax):
>>             self.edit_syntax_error()
>>         self.promptForLine(more)
>>         ###### indicate if we want to quit
>>         return not self.exit_now
>>
>>
>> class ShellProtocol(basic.LineReceiver):
>>     delimiter = '\n' # does not work with '\r\n' on Windows...
>>                      # this might be an issue with the #2157 patches?
>>
>>     def __init__(self, ipshell, banner, **kwargs):
>>         self.ipshell = ipshell
>>         self.banner = banner
>>         self.kwargs = kwargs
>>
>>     def connectionMade(self):
>>         #self.sendLine("Yay, type something!")
>>         # locals here are available in the shell:
>>         # (but in practice the locals of the ShellProtocol() call site
>>         # would be more interesting.)
>>         another_strange_local = 'hubabuba'
>>         from twisted.internet import reactor
>>         self.sheller = self.ipshell(self.banner
>>                 + '\n  quit.....quits via LineReceiver,'
>>                 + '\n  exit()...quits via IPython,'
>>                 + '\n  pause....test pausing the LineReceiver',
>>                 **self.kwargs)
>>
>>     def lineReceived(self, line):
>>         if line == 'quit':
>>             self.sendLine('OK quitting')
>>             self.transport.loseConnection()
>>             return
>>         if line == 'pause':
>>             self.sendLine('OK pausing for 2 seconds')
>>             self.pauseProducing()
>>             self.clearLineBuffer()
>>             # still receives keys typed during the pause,
>>             # no matter how many clearLineBuffer()s, I use.
>>             # might be a feature of Windows cmd... ?
>>             def restart():
>>                 self.clearLineBuffer()
>>                 self.resumeProducing()
>>                 self.clearLineBuffer()
>>             reactor.callLater(2, restart)
>>             return
>>         #self.sendLine("Echo: " + line)
>>         if not self.sheller.useLine(line): # processes line, prints output and next prompt
>>             self.sendLine("IPython wants to quit")
>>             self.transport.loseConnection()
>>         #self.transport.write("Yay, type more!")
>>
>>     #def rawDataReceived(self, data):
>>     #    self.sendLine('RawEcho: ' + str(data))
>>     #    self.transport.write("Yay, type more!")
>>
>>     def connectionLost(self, reason):
>>         try:
>>             self.ipshell.teardown()
>>         except IOError:
>>             pass # is raised by IPython code when you type quit
>>         # stop the reactor, only because this is meant to be run in Stdio.
>>         reactor.stop()
>>
>>
>> if __name__ == '__main__':
>>     main()
>>
>>
>> ------------------------------------------------------------------------
>>
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