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Python3并發(fā)寫文件與Python對比

更新時間：2019年11月20日 16:47:18 作者：川川籽

這篇文章主要介紹了Python3并發(fā)寫文件原理解析,文中通過示例代碼介紹的非常詳細(xì)，對大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價值,需要的朋友可以參考下

使用python2在進(jìn)行并發(fā)寫的時候，發(fā)現(xiàn)文件會亂掉，就是某一行中間會插入其他行的內(nèi)容。

但是在使用python3進(jìn)行并發(fā)寫的時候，無論是多進(jìn)程，還是多線程，都沒有出現(xiàn)這個問題，難道是python3的特性嗎？

import time
import os
import multiprocessing
from multiprocessing.dummy import Pool as ThreadPool


def 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)

上面代碼，多進(jìn)程并發(fā)寫結(jié)束后，校驗每一行的長度是否是設(shè)置好的長度。用python3反復(fù)運行，均通過測試沒有異常。

$ python3 --version
Python 3.7.4

$ python3 t.py
lines:10000, max len:1000, min:1000, avg:1000.00

如果用python2，則會出現(xiàn)異常：

$ python2 --version
Python 2.7.15

$ python2 t.py
Traceback (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內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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