How to pass a list as an environment variable?

Question

I use a list as part of a Python program, and wanted to convert that to an environment variable.

So, it's like this:

list1 = ['a.1','b.2','c.3'] for items in list1:     alpha,number = items.split('.')     print(alpha,number) 

which gives me, as expected:

a 1 b 2 c 3 

But when I try to set it as an environment variable, as:

export LIST_ITEMS = 'a.1', 'b.2', 'c.3' 

and do:

list1 = [os.environ.get("LIST_ITEMS")] for items in list1:     alpha,number = items.split('.')     print(alpha,number) 

I get an error: ValueError: too many values to unpack

How do I modify the way I pass the list, or get it so that I have the same output as without using env variables?

Answer 1

The rationale

I recommend using JSON if you want to have data structured in an environment variable. JSON is simple to write / read, can be written in a single line, parsers exist, developers know it.

The solution

To test, execute this in your shell:

$ export ENV_LIST_EXAMPLE='["Foo", "bar"]' 

Python code to execute in the same shell:

import os import json  env_list = json.loads(os.environ['ENV_LIST_EXAMPLE']) print(env_list) print(type(env_list)) 

gives

['Foo', 'bar'] <class 'list'> 

Package

Chances are high that you are interested in cfg_load

Debugging

If you see

JSONDecodeError: Expecting value: line 1 column 2 (char 1) 

You might have used single-quotes instead of double-quotes. While some JSON libraries accept that, the JSON standard clearly states that you need to use double-quotes:

Wrong: "['foo', 'bar']" Right: '["foo", "bar"]' 

Answer 2

I'm not sure why you'd do it through the environment variables, but you can do this:

export LIST_ITEMS ="a.1 b.2 c.3" 

And in Python:

list1 = [i.split(".") for i in os.environ.get("LIST_ITEMS").split(" ")]   for k, v in list1:     print(k, v)