os.getenv returns empty output - python

Question

I am new to python and encountering some issues while executing os commands.

I have set my environment variables like as shown below

SPARK_HOME = '/opt/spark'
HAIL_HOME  = '/opt/hail/hail'

When I type os.getenv('SPARK_HOME'), I get the below output

'/opt/spark/'

But when I type os.getenv('HAIL_HOME'), I get blank output

Please note that I type the above two commands from a virtual environment using jupyter notebook.

Can guide me with this issue?

HAIL_HOME should be 'HAIL_HOME', a string identifier not a variable. — sardok, Jun 23 '20 at 08:08
Sorry, updated the post. Even with `HAIL_HOME`, It returns empty output — The Great, Jun 23 '20 at 08:09
You may debug program's env variables by printing `os.environ`. If what you look for is missing there, you should probably add command or script that sets env variables and starts your app. — sardok, Jun 23 '20 at 08:14
Can you please help me with the second part of your comment? which is `you should probably add command or script that sets env variables and starts your app` — The Great, Jun 23 '20 at 08:16
Env variables are set by another program probably the shell. If an env variable is missing, you should investigate at one level below, where python script is started/executed. Thats why, it could be useful to add steps about how you set env variables and run python script. — sardok, Jun 23 '20 at 08:26
Yes, you are right. I set these variables in my python program jupyter notebook `SPARK_HOME = '/opt/spark' HAIL_HOME = '/opt/hail/hail'` — The Great, Jun 23 '20 at 08:27
but don't know why I am able to get the path of (os.getenv) for one variable and not for the other — The Great, Jun 23 '20 at 08:27
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/216475/discussion-between-the-great-and-sardok). — The Great, Jun 23 '20 at 08:30

score 1 · Accepted Answer · answered Jun 23 '20 at 09:47

Based on our discussion on chat, identified several issues.

Variable setting is confused with env variable setting. So correct way to set them should be like:

os.putenv('SPARK_HOME', '/opt/spark')
os.putenv('HAIL_HOME', '/opt/hail/hail')

Even the mistaken env variable set attempts, SPARK_HOME shows the correct value because jupyter process inherits that variable from the shell.

1 Answers1