Python:为什么打印语句和subprocess.call()输出不同步? [英] Python: why print statements and subprocess.call() output are out of sync?

问题描述

我正在运行以下代码(称为batch.py​​)

I am running the following piece of code (call it batch.py)

for config in keystoneConfig: 
    cmdlist = generate_cmd_list(config)
    print ' '.join(cmdlist)
    subprocess.call(cmdlist)

然后将batch.py​​的输出重定向到另一个文件.即

And redirecting the output of batch.py to another file. i.e.

./batch.py​​> output.txt

./batch.py > output.txt

但是我意识到subprocess.call()的所有输出都在print语句之前.为什么输出不同步?

But I realize that all the output from subprocess.call() goes before the print statement. Why is the output out of sync?

推荐答案

Python正在块缓冲其自身的输出，并且不会在subprocess.call()之前刷新它，因为您将其输出重定向到了文件而不是控制台.您将需要强制行缓冲或禁用缓冲，或者在子进程调用之前手动刷新.

Python is block buffering its own output and not flushing it before subprocess.call(), because you redirected its output to a file instead of the console; you would need to force line buffering or disable buffering, or manually flush before the subprocess call.

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