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Изворен канал @pythonotes · Post #201 · 13 јан.

Мы уже знаем, что на текущую сессию интерпретатора изменение PYTHONPATH никак не повлияет. Но если вы запустите дочерний процесс, то он унаследует окружение текущего процесса, а значит и изменения в любых переменных будут на него влиять. Вот небольшой пример: Объявляем переменную user@host:~$ export PYTHONPATH=/path1 Запускаем интерпретатор user@host:~$ python3 Проверим что в sys.path >>> import sys >>> print(sys.path) ['', '/path1', '/usr/lib/...', ...] Добавляем что-то в переменную >>> import os >>> os.emviron['PYTHONPATH'] = '/path1:/path2' >>> print(sys.path) ['', '/path1', '/usr/lib/...', ...] Изменений нет. Но давайте запустим дочерний процесс и посмотрим там >>> os.system('python3') # теперь мы находимся в другом процессе >>> import sys >>> print(sys.path) ['', '/path1', '/path2', '/usr/lib/...', ...] Тоже самое будет и с subprocess, так как по умолчанию текущее окружение тоже наследуется. >>> import subprocess >>> subprocess.call(['python3', '-c', 'import sys;print(sys.path)']) ['', '/path1', '/path2', '/usr/lib/...', ...] ______________________ Лучшей практикой является передача энвайронмента явно через аргумент env! import subprocess subprocess.call(cmd, env={'PYTHONPATH': '...'}) Это поможет точно понимать какое окружение будет у запускаемого процесса и при этом не изменять окружение текущего процесса. #basic

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djangoproject

@djangoproject · Post #157 · 06.09.2016 г., 19:55

https://docs.python.org/2/library/multiprocessing.html #multiprocessing is a package that supports spawning processes using an #API similar to the #threading module. The multiprocessing package offers both local and remote #concurrency, effectively side-stepping the Global Interpreter Lock by using subprocesses instead of #threads. Due to this, the multiprocessing module allows the programmer to fully leverage multiple processors on a given machine. It runs on both Unix and Windows.

djangoproject

@djangoproject · Post #118 · 08.08.2016 г., 11:44

https://docs.python.org/3/library/multiprocessing.html multiprocessing is a package that supports spawning processes using an API similar to the threading module. The multiprocessing package offers both local and remote concurrency, effectively side-stepping the Global Interpreter Lock by using subprocesses instead of threads. Due to this, the multiprocessing module allows the programmer to fully leverage multiple processors on a given machine. It runs on both Unix and Windows. The #multiprocessing module also introduces #APIs which do not have analogs in the #threading#module. A prime example of this is the Pool object which offers a convenient means of parallelizing the execution of a function across multiple input values, distributing the input data across processes (data #parallelism). The following example demonstrates the common practice of defining such functions in a module so that child processes can successfully import that module. This basic example of data parallelism using Pool,

djangoproject

@djangoproject · Post #107 · 02.08.2016 г., 15:22

https://github.com/python/asyncio The #asyncio#module provides infrastructure for writing #single-threaded concurrent code using #coroutines, #multiplexing#I/O access over sockets and other resources, running network clients and servers, and other related primitives. Here is a more detailed list of the package contents: a pluggable event loop with various system-specific implementations; transport and protocol abstractions (similar to those in Twisted); concrete support for TCP, UDP, SSL, subprocess pipes, delayed calls, and others (some may be system-dependent); a Future class that mimics the one in the concurrent.futures module, but adapted for use with the event loop; #coroutines and #tasks based on yield from (PEP 380), to help write concurrent code in a sequential fashion; cancellation support for Futures and coroutines; synchronization primitives for use between coroutines in a single thread, mimicking those in the #threading module; an interface for passing work off to a threadpool, for times when you absolutely, positively have to use a library that makes blocking I/O calls. Note: The implementation of asyncio was previously called "Tulip".