string - 如何在 Python 2 和 Python 3 中处理 subprocess.Popen 输出

Question

我有一个简单的函数来检查程序是否正在运行并根据需要返回一个 bool 值。它通过检查命令 ps -A 的输出来做到这一点。使用模块subprocess .我试图让这个函数在 Python 2 和 Python 3 中都能工作，但遇到以下错误:

TypeError: a bytes-like object is required, not 'str'

应该如何更改函数以便它可以在 Python 2 和 Python 3 中工作？

import subprocess

def running(program):
    results = subprocess.Popen(
        ["ps", "-A"],
        stdout = subprocess.PIPE
    ).communicate()[0].split("\n")
    matches_current = [
        line for line in results if program in line and "defunct" not in line
    ]
    if matches_current:
        return True
    else:
        return False

编辑:遵循@Josh 的一些指导，我已将换行符字符串分隔符更改为字节码，但是我仍然遇到类似的问题:

>>> import subprocess
>>> def running(program):
...     results = subprocess.Popen(
...         ["ps", "-A"],
...         stdout = subprocess.PIPE
...     ).communicate()[0].split(b"\n")
...     matches_current = [
...         line for line in results if program in line and "defunct" not in line
...     ]
...     if matches_current:
...         return True
...     else:
...         return False
... 
>>> running("top")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 7, in running
  File "<stdin>", line 7, in <listcomp>
TypeError: a bytes-like object is required, not 'str'

Answer 1

使用像 b"\n" 这样的字节串而不是简单的 "\n" , 并使用 program.encode()而不是 program (假设你被传递一个字符串):

results = subprocess.Popen(
    ["ps", "-A"],
    stdout = subprocess.PIPE
).communicate()[0].split(b"\n")
matches_current = [
    line for line in results if program.encode() in line and b"defunct" not in line
]

这是因为在 Python 3 中， subprocess.Popen.communicate默认情况下返回字节而不是字符串。在 Python 2.6+ 中， b"\n" == "\n" ，所以你不应该有任何问题。