Python3并发写文件与Python对比

Python  /  管理员 发布于 7年前   415

这篇文章主要介绍了Python3并发写文件原理解析,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下

使用python2在进行并发写的时候，发现文件会乱掉，就是某一行中间会插入其他行的内容。

但是在使用python3进行并发写的时候，无论是多进程，还是多线程，都没有出现这个问题，难道是python3的特性吗？

import timeimport osimport multiprocessingfrom multiprocessing.dummy import Pool as ThreadPooldef write(val, file):  w = open(file, "a")  for i in range(100):    w.write("%s\n" % val)    time.sleep(0.001)def thread_write(file):  res, pools = [], ThreadPool(10)  for i in range(10):    val = str(i) * 1000    res.append(pools.apply_async(func=write, args=(val, file, )))  while res:    for ret in res:      if ret.ready():        res.remove(ret)    time.sleep(0.01)def mutil_write(file):  pools = multiprocessing.Pool(processes=10)  res = []  for i in range(100):    res.append(pools.apply_async(thread_write, args=(file, )))  while res:    for ret in res:      if ret.ready():        res.remove(ret)    time.sleep(0.01)if __name__ == '__main__':  file = "./write_test"  mutil_write(file)  with open(file) as fb:    lines = 0    line_len = []    for line in fb:      lines += 1      line = line.strip()      line_len.append(len(line))      if len(line) != 1000:        raise(Exception("error line: %s, len: %d" % (line, len(line))))    print("lines:%d, max len:%d, min:%d, avg:%.2f" % (lines, max(line_len), min(line_len), sum(line_len)/len(line_len)))  os.remove(file)

上面代码，多进程并发写结束后，校验每一行的长度是否是设置好的长度。用python3反复运行，均通过测试没有异常。

$ python3 --versionPython 3.7.4$ python3 t.pylines:10000, max len:1000, min:1000, avg:1000.00

如果用python2，则会出现异常：

$ python2 --versionPython 2.7.15$ python2 t.pyTraceback (most recent call last): File "t.py", line 49, in <module>  raise(Exception("error line: %s, len: %d" % (line, len(line))))Exception: error line: 333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333330000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000, len: 1092

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。