Lib/multiprocessing/__init__.py

   1 #
   2 # Package analogous to 'threading.py' but using processes
   3 #
   4 # multiprocessing/__init__.py
   5 #
   6 # This package is intended to duplicate the functionality (and much of
   7 # the API) of threading.py but uses processes instead of threads.  A
   8 # subpackage 'multiprocessing.dummy' has the same API but is a simple
   9 # wrapper for 'threading'.
  10 #
  11 # Try calling `multiprocessing.doc.main()` to read the html
  12 # documentation in in a webbrowser.
  13 #
  14 #
  15 # Copyright (c) 2006-2008, R Oudkerk
  16 # All rights reserved.
  17 #
  18 # Redistribution and use in source and binary forms, with or without
  19 # modification, are permitted provided that the following conditions
  20 # are met:
  21 #
  22 # 1. Redistributions of source code must retain the above copyright
  23 #    notice, this list of conditions and the following disclaimer.
  24 # 2. Redistributions in binary form must reproduce the above copyright
  25 #    notice, this list of conditions and the following disclaimer in the
  26 #    documentation and/or other materials provided with the distribution.
  27 # 3. Neither the name of author nor the names of any contributors may be
  28 #    used to endorse or promote products derived from this software
  29 #    without specific prior written permission.
  30 #
  31 # THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
  32 # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  33 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  34 # ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  35 # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  36 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  37 # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  38 # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  39 # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  40 # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  41 #
  42
  43 __version__ = '0.70a1'
  44
  45 __all__ = [
  46     'Process', 'current_process', 'active_children', 'freeze_support',
  47     'Manager', 'Pipe', 'cpu_count', 'log_to_stderr', 'get_logger',
  48     'allow_connection_pickling', 'BufferTooShort', 'TimeoutError',
  49     'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Condition',
  50     'Event', 'Queue', 'JoinableQueue', 'Pool', 'Value', 'Array',
  51     'RawValue', 'RawArray'
  52     ]
  53
  54 __author__ = 'R. Oudkerk (r.m.oudkerk@gmail.com)'
  55
  56 #
  57 # Imports
  58 #
  59
  60 import os
  61 import sys
  62
  63 from multiprocessing.process import Process, current_process, active_children
  64
  65 #
  66 # Exceptions
  67 #
  68
  69 class ProcessError(Exception):
  70     pass
  71
  72 class BufferTooShort(ProcessError):
  73     pass
  74
  75 class TimeoutError(ProcessError):
  76     pass
  77
  78 class AuthenticationError(ProcessError):
  79     pass
  80
  81 # This is down here because _multiprocessing uses BufferTooShort
  82 import _multiprocessing
  83
  84 #
  85 # Definitions not depending on native semaphores
  86 #
  87
  88 def Manager():
  89     '''
  90     Returns a manager associated with a running server process
  91
  92     The managers methods such as `Lock()`, `Condition()` and `Queue()`
  93     can be used to create shared objects.
  94     '''
  95     from multiprocessing.managers import SyncManager
  96     m = SyncManager()
  97     m.start()
  98     return m
  99
 100 def Pipe(duplex=True):
 101     '''
 102     Returns two connection object connected by a pipe
 103     '''
 104     from multiprocessing.connection import Pipe
 105     return Pipe(duplex)
 106
 107 def cpu_count():
 108     '''
 109     Returns the number of CPUs in the system
 110     '''
 111     if sys.platform == 'win32':
 112         try:
 113             num = int(os.environ['NUMBER_OF_PROCESSORS'])
 114         except (ValueError, KeyError):
 115             num = 0
 116     elif sys.platform == 'darwin':
 117         try:
 118             num = int(os.popen('sysctl -n hw.ncpu').read())
 119         except ValueError:
 120             num = 0
 121     else:
 122         try:
 123             num = os.sysconf('SC_NPROCESSORS_ONLN')
 124         except (ValueError, OSError, AttributeError):
 125             num = 0
 126
 127     if num >= 1:
 128         return num
 129     else:
 130         raise NotImplementedError('cannot determine number of cpus')
 131
 132 def freeze_support():
 133     '''
 134     Check whether this is a fake forked process in a frozen executable.
 135     If so then run code specified by commandline and exit.
 136     '''
 137     if sys.platform == 'win32' and getattr(sys, 'frozen', False):
 138         from multiprocessing.forking import freeze_support
 139         freeze_support()
 140
 141 def get_logger():
 142     '''
 143     Return package logger -- if it does not already exist then it is created
 144     '''
 145     from multiprocessing.util import get_logger
 146     return get_logger()
 147
 148 def log_to_stderr(level=None):
 149     '''
 150     Turn on logging and add a handler which prints to stderr
 151     '''
 152     from multiprocessing.util import log_to_stderr
 153     return log_to_stderr(level)
 154
 155 def allow_connection_pickling():
 156     '''
 157     Install support for sending connections and sockets between processes
 158     '''
 159     from multiprocessing import reduction
 160
 161 #
 162 # Definitions depending on native semaphores
 163 #
 164
 165 def Lock():
 166     '''
 167     Returns a non-recursive lock object
 168     '''
 169     from multiprocessing.synchronize import Lock
 170     return Lock()
 171
 172 def RLock():
 173     '''
 174     Returns a recursive lock object
 175     '''
 176     from multiprocessing.synchronize import RLock
 177     return RLock()
 178
 179 def Condition(lock=None):
 180     '''
 181     Returns a condition object
 182     '''
 183     from multiprocessing.synchronize import Condition
 184     return Condition(lock)
 185
 186 def Semaphore(value=1):
 187     '''
 188     Returns a semaphore object
 189     '''
 190     from multiprocessing.synchronize import Semaphore
 191     return Semaphore(value)
 192
 193 def BoundedSemaphore(value=1):
 194     '''
 195     Returns a bounded semaphore object
 196     '''
 197     from multiprocessing.synchronize import BoundedSemaphore
 198     return BoundedSemaphore(value)
 199
 200 def Event():
 201     '''
 202     Returns an event object
 203     '''
 204     from multiprocessing.synchronize import Event
 205     return Event()
 206
 207 def Queue(maxsize=0):
 208     '''
 209     Returns a queue object
 210     '''
 211     from multiprocessing.queues import Queue
 212     return Queue(maxsize)
 213
 214 def JoinableQueue(maxsize=0):
 215     '''
 216     Returns a queue object
 217     '''
 218     from multiprocessing.queues import JoinableQueue
 219     return JoinableQueue(maxsize)
 220
 221 def Pool(processes=None, initializer=None, initargs=()):
 222     '''
 223     Returns a process pool object
 224     '''
 225     from multiprocessing.pool import Pool
 226     return Pool(processes, initializer, initargs)
 227
 228 def RawValue(typecode_or_type, *args):
 229     '''
 230     Returns a shared object
 231     '''
 232     from multiprocessing.sharedctypes import RawValue
 233     return RawValue(typecode_or_type, *args)
 234
 235 def RawArray(typecode_or_type, size_or_initializer):
 236     '''
 237     Returns a shared array
 238     '''
 239     from multiprocessing.sharedctypes import RawArray
 240     return RawArray(typecode_or_type, size_or_initializer)
 241
 242 def Value(typecode_or_type, *args, **kwds):
 243     '''
 244     Returns a synchronized shared object
 245     '''
 246     from multiprocessing.sharedctypes import Value
 247     return Value(typecode_or_type, *args, **kwds)
 248
 249 def Array(typecode_or_type, size_or_initializer, **kwds):
 250     '''
 251     Returns a synchronized shared array
 252     '''
 253     from multiprocessing.sharedctypes import Array
 254     return Array(typecode_or_type, size_or_initializer, **kwds)
 255
 256 #
 257 #
 258 #
 259
 260 if sys.platform == 'win32':
 261
 262     def set_executable(executable):
 263         '''
 264         Sets the path to a python.exe or pythonw.exe binary used to run
 265         child processes on Windows instead of sys.executable.
 266         Useful for people embedding Python.
 267         '''
 268         from multiprocessing.forking import set_executable
 269         set_executable(executable)
 270
 271     __all__ += ['set_executable']