Checking if an environment variable exists and is set to True

Question

So, I want to check and verify if a given variable "abc" exists and that it's true. If the variable exist and is False, then I want it to go to else. Here is how I got it to work in python:

env = os.environ.copy()
if "abc" in env and env['abc'] == "True":
    print "Works"
else:
    print "Doesn't work"

Is there a better way to do it?

that string of identical answers all within 10sec of eachother was impressive... — Aaron, Jun 12 '17 at 17:35
Are you actually looking for a string of the value "True", or are you looking for a boolean `True`? — idjaw, Jun 12 '17 at 17:35
If `env` is `os.environ` and these are literally environment variables, it'll be a string `"True"`, but it's not clear what `env` is and what preprocessing may have been done. — user2357112, Jun 12 '17 at 17:43
@idjaw I think because I am checking for env variable I am not sure if I can check for boolean! — Jason, Jun 12 '17 at 17:47
Possible duplicate of [How do I check if a variable exists?](https://stackoverflow.com/questions/843277/how-do-i-check-if-a-variable-exists) — victor, Jun 12 '17 at 18:05
@VictorC. I tried your below suggestion in Python 2.7.9 but doesn't work there. Essentially I want something that works on 2.7 and 3.0 — Jason, Jun 12 '17 at 20:41
@Jason That's strange, `locals()` and `globals()` exists in Python 2.7 as well...it works for me when I try it with version 2.7. What error are you getting? — victor, Jun 12 '17 at 21:07
@VictorC. So I did an export abc=True but the locals().get('abc') gives me null in 2.7.9. Do you have any other imports apart from sys or os? — Jason, Jun 13 '17 at 00:19
@VictorC. Now I understand how locals and globals work. Given that I am not sure if there is a need for locals or globals as I can just do `env.get('abc')`. But that still leaves the "True" or "False" open as any of the output here doesnt check if the variable is True/False. How do I go to else if the variable exist and is False ? — Jason, Jun 13 '17 at 00:35
@Jason `os.environ` is still a dictionary similar to local variables. You can do the same thing you did with globals, namely `if env.get('abc')=='True'` — victor, Jun 13 '17 at 17:42

victor · Accepted Answer · 2017-06-13T17:43:21.173

13

You can check to see if the variable is in the dictionaries returned by globals() and locals(). (Thank you to Aaron for reminding me to add the full code)

For a local variable:

if locals().get('abc'):
    print(abc)

For a global variable:

if globals().get('abc'):
    print(abc)

For an environment variable:

if os.environ.get('abc')=='True':
    #abc is set to True

More information here:

https://docs.python.org/3/library/functions.html#locals https://docs.python.org/3/library/functions.html#globals

edited Jun 13 '17 at 17:43

answered Jun 12 '17 at 17:40

victor

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the full answer would then look like `if locals().get('abc') == True:` (or `...globals()...`) – Aaron Jun 12 '17 at 17:55

score 10 · Answer 2 · answered Jun 12 '17 at 17:34

10

You can use:

env.get("abc", False)

False is the default value if "abc" is not in env.

answered Jun 12 '17 at 17:34

Bubble Bubble Bubble Gut

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Tyler Bell · Answer 3 · 2017-06-12T18:34:06.927

1

You could use a Try Except Block.

try:
    # Try calling ABC here anyway you like
    # Here I am just printing it
    print(abc)
except NameError:
    print("Variable ABC does not exist")

edited Jun 12 '17 at 18:34

answered Jun 12 '17 at 17:36

Tyler Bell

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If you do it this way, you should do `except NameError:` instead of blindly catching any exception – trent Jun 12 '17 at 17:47

score 0 · Answer 4 · answered Jun 12 '17 at 17:34

0

It's enough get it from env, I think

env.get('abc')

answered Jun 12 '17 at 17:34

vZ10

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Checking if an environment variable exists and is set to True

4 Answers4