How can I retrieve environment variables from remote system in Python?

Question

I'm trying to retrieve environment variables of a remote Linux server in Python. Alternatively, if I could use the variable name in the command I'm executing, that'd be great as well. The calls I'm making should work, as far as I can tell, but I'm getting back garbage. I have set up public-key authentication, so no password required.

Effort 1:

devdir = subprocess.check_output(["ssh", connectstring, "echo $DEVDIR"])

Effort 2:

ret = subprocess.check_output(["ssh", connectstring, 
    "$DEVDIR/{0}".format(testpath)])

connectstring is user@ip and works fine. $DEVDIR is the remote variable I want to use and contains a path. testpath is the path to the script I'm trying to execute, rooted at $DEVDIR.

Effort 1 returns "\n", Effort 2 fails to resolve $DEVDIR remotely.

---

Effort 3:

import paramiko
...
ssh = paramiko.SSHClient()
ssh.connect(ip, user)    # succeeds
stdin, stdout, stderr = ssh.exec_command("echo $DEVDIR")

result: stdout.readlines() = "\n"

Answer 1

If the environment variable is set in .bashrc, you can force the remote command to run under a login shell with the -l option. The following...

devdir = subprocess.check_output(["ssh", connectstring, "sh -l -c 'echo $DEVDIR'"])

...works for me.