[英]Python: How to read stdout of subprocess in a nonblocking way
我正在嘗試制作一個簡單的 python 腳本,該腳本啟動一個子進程並監視其標准 output。 這是代碼中的一個片段:
process = subprocess.Popen([path_to_exe, os.path.join(temp_dir,temp_file)], stdout=subprocess.PIPE)
while True:
output=process.stdout.readline()
print "test"
問題是腳本掛在output=process.stdout.readline()
上,並且print "test"
行僅在子進程終止后執行。
有沒有辦法讀取標准 output 並打印它而不必等待子進程終止?
我開始的子進程是一個 Windows 二進制文件,我沒有它的源代碼。
我發現了幾個類似的問題,但答案僅適用於 Linux 或者如果我有我開始的 suprocess 的來源。
檢查選擇模塊
import subprocess
import select
import time
x=subprocess.Popen(['/bin/bash','-c',"while true; do sleep 5; echo yes; done"],stdout=subprocess.PIPE)
y=select.poll()
y.register(x.stdout,select.POLLIN)
while True:
if y.poll(1):
print x.stdout.readline()
else:
print "nothing here"
time.sleep(1)
非posix系統的螺紋解決方案:
import subprocess
from threading import Thread
import time
linebuffer=[]
x=subprocess.Popen(['/bin/bash','-c',"while true; do sleep 5; echo yes; done"],stdout=subprocess.PIPE)
def reader(f,buffer):
while True:
line=f.readline()
if line:
buffer.append(line)
else:
break
t=Thread(target=reader,args=(x.stdout,linebuffer))
t.daemon=True
t.start()
while True:
if linebuffer:
print linebuffer.pop(0)
else:
print "nothing here"
time.sleep(1)
你可以試試這個:
import subprocess
import os
""" Continuously print command output """
""" Will only work if there are newline characters in the output. """
def run_cmd(command):
popen = subprocess.Popen(command, stdout=subprocess.PIPE)
return iter(popen.stdout.readline, b"")
for line in run_cmd([path_to_exe, os.path.join(temp_dir,temp_file)]):
print(line), # the comma keeps python from adding an empty line
從 python 3.5 開始,您可以使用os.set_blocking()
如下。
import os
import subprocess
process = subprocess.Popen([path_to_exe, os.path.join(temp_dir,temp_file)], stdout=subprocess.PIPE)
os.set_blocking(process.stdout.fileno(), False) #<----- HERE
while True:
output=process.stdout.readline()
print "test"
if process.poll() is not None:
break
rc = process.poll()
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