"""Utilities for launching kernels """ # Copyright (c) IPython Development Team. # Distributed under the terms of the Modified BSD License. import os import sys from subprocess import Popen, PIPE from IPython.utils.encoding import getdefaultencoding from IPython.utils.py3compat import cast_bytes_py2 def swallow_argv(argv, aliases=None, flags=None): """strip frontend-specific aliases and flags from an argument list For use primarily in frontend apps that want to pass a subset of command-line arguments through to a subprocess, where frontend-specific flags and aliases should be removed from the list. Parameters ---------- argv : list(str) The starting argv, to be filtered aliases : container of aliases (dict, list, set, etc.) The frontend-specific aliases to be removed flags : container of flags (dict, list, set, etc.) The frontend-specific flags to be removed Returns ------- argv : list(str) The argv list, excluding flags and aliases that have been stripped """ if aliases is None: aliases = set() if flags is None: flags = set() stripped = list(argv) # copy swallow_next = False was_flag = False for a in argv: if a == '--': break if swallow_next: swallow_next = False # last arg was an alias, remove the next one # *unless* the last alias has a no-arg flag version, in which # case, don't swallow the next arg if it's also a flag: if not (was_flag and a.startswith('-')): stripped.remove(a) continue if a.startswith('-'): split = a.lstrip('-').split('=') name = split[0] # we use startswith because argparse accepts any arg to be specified # by any leading section, as long as it is unique, # so `--no-br` means `--no-browser` in the notebook, etc. if any(alias.startswith(name) for alias in aliases): stripped.remove(a) if len(split) == 1: # alias passed with arg via space swallow_next = True # could have been a flag that matches an alias, e.g. `existing` # in which case, we might not swallow the next arg was_flag = name in flags elif len(split) == 1 and any(flag.startswith(name) for flag in flags): # strip flag, but don't swallow next, as flags don't take args stripped.remove(a) # return shortened list return stripped def make_ipkernel_cmd(mod='ipython_kernel', executable=None, extra_arguments=[], **kw): """Build Popen command list for launching an IPython kernel. Parameters ---------- mod : str, optional (default 'ipython_kernel') A string of an IPython module whose __main__ starts an IPython kernel executable : str, optional (default sys.executable) The Python executable to use for the kernel process. extra_arguments : list, optional A list of extra arguments to pass when executing the launch code. Returns ------- A Popen command list """ if executable is None: executable = sys.executable arguments = [ executable, '-m', mod, '-f', '{connection_file}' ] arguments.extend(extra_arguments) return arguments def launch_kernel(cmd, stdin=None, stdout=None, stderr=None, env=None, independent=False, cwd=None, **kw ): """ Launches a localhost kernel, binding to the specified ports. Parameters ---------- cmd : Popen list, A string of Python code that imports and executes a kernel entry point. stdin, stdout, stderr : optional (default None) Standards streams, as defined in subprocess.Popen. independent : bool, optional (default False) If set, the kernel process is guaranteed to survive if this process dies. If not set, an effort is made to ensure that the kernel is killed when this process dies. Note that in this case it is still good practice to kill kernels manually before exiting. cwd : path, optional The working dir of the kernel process (default: cwd of this process). Returns ------- Popen instance for the kernel subprocess """ # Popen will fail (sometimes with a deadlock) if stdin, stdout, and stderr # are invalid. Unfortunately, there is in general no way to detect whether # they are valid. The following two blocks redirect them to (temporary) # pipes in certain important cases. # If this process has been backgrounded, our stdin is invalid. Since there # is no compelling reason for the kernel to inherit our stdin anyway, we'll # place this one safe and always redirect. redirect_in = True _stdin = PIPE if stdin is None else stdin # If this process in running on pythonw, we know that stdin, stdout, and # stderr are all invalid. redirect_out = sys.executable.endswith('pythonw.exe') if redirect_out: blackhole = open(os.devnull, 'w') _stdout = blackhole if stdout is None else stdout _stderr = blackhole if stderr is None else stderr else: _stdout, _stderr = stdout, stderr env = env if (env is not None) else os.environ.copy() encoding = getdefaultencoding(prefer_stream=False) kwargs = dict( stdin=_stdin, stdout=_stdout, stderr=_stderr, cwd=cwd, env=env, ) # Spawn a kernel. if sys.platform == 'win32': # Popen on Python 2 on Windows cannot handle unicode args or cwd cmd = [ cast_bytes_py2(c, encoding) for c in cmd ] if cwd: cwd = cast_bytes_py2(cwd, sys.getfilesystemencoding() or 'ascii') kwargs['cwd'] = cwd from .win_interrupt import create_interrupt_event # Create a Win32 event for interrupting the kernel # and store it in an environment variable. interrupt_event = create_interrupt_event() env["JPY_INTERRUPT_EVENT"] = str(interrupt_event) # deprecated old env name: env["IPY_INTERRUPT_EVENT"] = env["JPY_INTERRUPT_EVENT"] try: from _winapi import DuplicateHandle, GetCurrentProcess, \ DUPLICATE_SAME_ACCESS, CREATE_NEW_PROCESS_GROUP except: from _subprocess import DuplicateHandle, GetCurrentProcess, \ DUPLICATE_SAME_ACCESS, CREATE_NEW_PROCESS_GROUP # Launch the kernel process if independent: kwargs['creationflags'] = CREATE_NEW_PROCESS_GROUP else: pid = GetCurrentProcess() handle = DuplicateHandle(pid, pid, pid, 0, True, # Inheritable by new processes. DUPLICATE_SAME_ACCESS) env['JPY_PARENT_PID'] = str(int(handle)) proc = Popen(cmd, **kwargs) # Attach the interrupt event to the Popen objet so it can be used later. proc.win32_interrupt_event = interrupt_event else: if independent: kwargs['preexec_fn'] = lambda: os.setsid() else: env['JPY_PARENT_PID'] = str(os.getpid()) proc = Popen(cmd, **kwargs) # Clean up pipes created to work around Popen bug. if redirect_in: if stdin is None: proc.stdin.close() return proc __all__ = [ 'swallow_argv', 'make_ipkernel_cmd', 'launch_kernel', ]