Python subprocess/Popen with a modified environment

user_263109 0
Viewed 284601

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?

popen subprocess python
8 Answers

I think os.environ.copy() is better if you don't intend to modify the os.environ for the current process:

import subprocess, os
my_env = os.environ.copy()
my_env["PATH"] = "/usr/sbin:/sbin:" + my_env["PATH"]
subprocess.Popen(my_command, env=my_env)
user_5437530

you might use my_env.get("PATH", '') instead of my_env["PATH"] in case PATH somehow not defined in the original environment, but other than that it looks fine.

user_128550

The env parameter accepts a dictionary. You can simply take os.environ, add a key (your desired variable) (to a copy of the dict if you must) to that and use it as a parameter to Popen.

user_2296020

In certain circumstances you may want to only pass down the environment variables your subprocess needs, but I think you've got the right idea in general (that's how I do it too).

user_247620
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