FileNotFoundError: [WinError 2] The system can't find the specified file

Question

我目前正在学习如何使用模块 subprocess，我刚刚开始学习我的新书。立即，我收到一条我不理解的错误消息。

Traceback (most recent call last):
  File "D:/me/Python/subprocess.py", line 3, in <module>
    proc = subprocess.Popen(['echo', 'Hello there'], stdout=subprocess.PIPE)
  File "C:\Python34\lib\subprocess.py", line 859, in __init__
    restore_signals, start_new_session)
  File "C:\Python34\lib\subprocess.py", line 1112, in _execute_child
    startupinfo)
FileNotFoundError: [WinError 2] The system can't find the specified file

我想不通这里有什么问题:

import subprocess

proc = subprocess.Popen(['echo', 'Hello there'], stdout=subprocess.PIPE)
out, err = proc.communicate()
print(out.decode('utf-8'))

在书中他们说这段代码应该在屏幕上打印 'Hello there' 但由于某些原因，它没有。

这里有什么问题？我目前正在使用 python 3.4.3，如果对您有帮助的话。

Answer 1

echo 不是可以执行的程序，而是 Windows 命令行解释器中可用的 shell 命令 cmd.exe.

为了执行shell命令，你需要将shell=True传递给Popen:

proc = subprocess.Popen(['echo', 'Hello there'], stdout=subprocess.PIPE, shell=True)
#                                                                        ^^^^^^^^^^

FileNotFoundError: [WinError 2] The system can't find the specified file

FileNotFoundError: [WinError 2] The system can't find the specified file

python

subprocess

python-3.x