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