search
HomeBackend DevelopmentPython Tutorial简单分析Python中用fork()函数生成的子进程

python的os module中有fork()函数用于生成子进程,生成的子进程是父进程的镜像,但是它们有各自的地址空间,子进程复制一份父进程内存给自己,两个进程之 间的执行是相互独立的,其执行顺序可以是不确定的、随机的、不可预测的,这点与多线程的执行顺序相似。 

import os
def child():
  print 'A new child:', os.getpid()
  print 'Parent id is:', os.getppid()
  os._exit(0)
def parent():
  while True:
    newpid=os.fork()
    print newpid
    if newpid==0:
      child()
    else:
      pids=(os.getpid(),newpid)
      print "parent:%d,child:%d"%pids
      print "parent parent:",os.getppid()    
    if raw_input()=='q':
      break
parent()

    在我们加载了os模块之后,我们parent函数中fork()函数生成了一个子进程,返回值newpid有两个,一个为0,用以表示子进程,一个是大于 0的整数,用以表示父进程,这个常数正是子进程的pid. 通过print语句我们可以清晰看到两个返回值。如果fork()返回值是一个负值,则表明子进程生成不成功(这个简单程序中没有考虑这种情况)。如果 newpid==0,则表明我们进入到了子进程,也就是child()函数中,在子进程中我们输出了自己的id和父进程的id。如果进入了else语句, 则表明newpid>0,我们进入到父进程中,在父进程中os.getpid()得到自己的id,fork()返回值newpid表示了子进程的id,同时我们输出了父进程的父进程的id. 通过实验我们可以看到if和else语句的执行顺序是不确定的,子、父进程的执行顺序由操作系统的调度算法来决定。

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Is Tuple Comprehension possible in Python? If yes, how and if not why?Is Tuple Comprehension possible in Python? If yes, how and if not why?Apr 28, 2025 pm 04:34 PM

Article discusses impossibility of tuple comprehension in Python due to syntax ambiguity. Alternatives like using tuple() with generator expressions are suggested for creating tuples efficiently.(159 characters)

What are Modules and Packages in Python?What are Modules and Packages in Python?Apr 28, 2025 pm 04:33 PM

The article explains modules and packages in Python, their differences, and usage. Modules are single files, while packages are directories with an __init__.py file, organizing related modules hierarchically.

What is docstring in Python?What is docstring in Python?Apr 28, 2025 pm 04:30 PM

Article discusses docstrings in Python, their usage, and benefits. Main issue: importance of docstrings for code documentation and accessibility.

What is a lambda function?What is a lambda function?Apr 28, 2025 pm 04:28 PM

Article discusses lambda functions, their differences from regular functions, and their utility in programming scenarios. Not all languages support them.

What is a break, continue and pass in Python?What is a break, continue and pass in Python?Apr 28, 2025 pm 04:26 PM

Article discusses break, continue, and pass in Python, explaining their roles in controlling loop execution and program flow.

What is a pass in Python?What is a pass in Python?Apr 28, 2025 pm 04:25 PM

The article discusses the 'pass' statement in Python, a null operation used as a placeholder in code structures like functions and classes, allowing for future implementation without syntax errors.

Can we Pass a function as an argument in Python?Can we Pass a function as an argument in Python?Apr 28, 2025 pm 04:23 PM

Article discusses passing functions as arguments in Python, highlighting benefits like modularity and use cases such as sorting and decorators.

What is the difference between / and // in Python?What is the difference between / and // in Python?Apr 28, 2025 pm 04:21 PM

Article discusses / and // operators in Python: / for true division, // for floor division. Main issue is understanding their differences and use cases.Character count: 158

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

PhpStorm Mac version

PhpStorm Mac version

The latest (2018.2.1) professional PHP integrated development tool

SecLists

SecLists

SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.

SublimeText3 English version

SublimeText3 English version

Recommended: Win version, supports code prompts!