Python subprocess/Popen with a modified environment
I believe that running an external command with a slightly modified environment is a very common case. That's how I tend to do it:
import subprocess, os
my_env = os.environ
my_env["PATH"] = "/usr/sbin:/sbin:" + my_env["PATH"]
subprocess.Popen(my_command, env=my_env)
I've got a gut feeling that there's a better way; does it look alright?
我认为os.environ.copy()更好，如果你不打算修改当前进程的os.environ：
import subprocess, os
my_env = os.environ.copy()
my_env["PATH"] = "/usr/sbin:/sbin:" + my_env["PATH"]
subprocess.Popen(my_command, env=my_env)
That depends on what the issue is. If it's to clone and modify the environment one solution could be:
subprocess.Popen(my_command, env=dict(os.environ, PATH="path"))
But that somewhat depends on that the replaced variables are valid python identifiers, which they most often are (how often do you run into environment variable names that are not alphanumeric+underscore or variables that starts with a number?).
Otherwise you'll could write something like:
subprocess.Popen(my_command, env=dict(os.environ,
**{"Not valid python name":"value"}))
In the very odd case (how often do you use control codes or non-ascii characters in environment variable names?) that the keys of the environment are bytes you can't (on python3) even use that construct.
As you can see the techniques (especially the first) used here benefits on the keys of the environment normally is valid python identifiers, and also known in advance (at coding time), the second approach has issues. In cases where that isn't the case you should probably look for another approach.
如果PATH以某种方式未在原始环境中定义，则可以使用my_env.get("PATH", '')而不是my_env["PATH"] ，但my_env["PATH"]看起来不错。