Reading bash environment variable set using parameter substitution into Python variable

Question

I have the following environment variables in my .env file:

DT="2019-01-01"
X=${DT//-/}

The variable X has been set using Bash's parameter replacement, using the ${parameter//pattern/string} format to replace all occurrences (Documentation here).

Now, to read the environment variables into Python, I have created a Python class Config in a file config.py:

from dotenv import find_dotenv, load_dotenv
import os

class Config:
    def __init__(self):
        load_dotenv(find_dotenv())

        self.X = os.environ.get('X')

In a python shell, I run:

In [1]: from config import Config

In [2]: c = Config()

In [3]: c.X
Out[3]: ''

Here c.X is an empty string '', where as I want it to be '20190101'.

How do I load the correct value of the environment variable into a python variable?

Edit: When I type echo $X in a bash script, it prints the correct value. For example, a bash script sample.sh:

#!/bin/bash
source .env

echo $X

When run, I get:

$ sh sample.sh
20190101

also try $ env in your bash first to make sure X is set to what you want. — hiro protagonist
– hiro protagonist, Commented Mar 27, 2019 at 15:50
Have edited the question for clarifications @hiroprotagonist — IM94
– IM94, Commented Mar 27, 2019 at 15:55
how do you start python then? you may have to export X in bash... — hiro protagonist
– hiro protagonist, Commented Mar 27, 2019 at 16:05
@hiroprotagonist, I added the export, it works the way I need it to now, thanks! :D — IM94
– IM94, Commented Mar 27, 2019 at 16:23

IM94 · Accepted Answer · 2019-04-04 08:26:59Z

2

I added an export in my .env file in this way:

DT="2019-01-01"
export X=${DT//-/}

This allowed me to get the correct value of c.X in Python.

answered Apr 4, 2019 at 8:26

IM94

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Comments

mossymountain · Accepted Answer · 2019-03-27 16:17:34Z

0

Dotenv does not use Bash; it parses the file internally. See the dotenv GitHub page.

Directly use DT instead:

self.X = os.environ.get('DT').replace('-', '')

answered Mar 27, 2019 at 16:17

mossymountain

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1 Comment

IM94 Over a year ago

I need to use the variable X without hyphens as a part of another variable name later on in my .env file as well. It would be better if I could resolve this in the .env file itself rather than in Python.

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