Export a variable from bash and use it in Python

Question

I am trying to write a script which is executing couple of things on a Linux server and I would like to use bash for most of the Linux specific commands and only use Python for the most complex stuff, but in order to do that I will need to export some variables from the bash script and use them in the python script and I didn't find a way how I can do that. So I have tried to create two very little scripts to test this functionality: 1.sh is a bash script

#!/bin/bash

test_var="Test Variable"
export test_var
echo "1.sh has been executed"
python 2.sh

2.sh is a Python script:

#!/usr/bin/env python3

print("The python script has been invoked successfully")
print(test_var)

As you can guess when I execute the first script the second fails with the error about unknown variable:

$ ./1.sh
1.sh has been executed
The python script has been invoked successfully
Traceback (most recent call last):
  File "2.sh", line 4, in <module>
    print(test_var)
NameError: name 'test_var' is not defined

The reason why I am trying to do that is because I am more comfortable with bash and I want to use $1, $2 variables in bash. Is this also possible in Python?

[EDIT] - I have just found out how I can use $1 and $2 it in Python. You need to use sys.argv[1] and sys.argv[2] and import the sys module import sys

Why not just use os.environ['test_var'] if you wan't to access environment variables? — user1767754
– user1767754, Commented May 29, 2018 at 8:23
You also could pass variable to Python scripts: python 1.py "variable-value" — Arount
– Arount, Commented May 29, 2018 at 8:25

Sergio Ivanuzzo · Accepted Answer · 2019-03-01 12:55:57Z

8

To use environment variables from your python script you need to call:

import os
os.environ['test_var']

os.environ is a dictionary with all the environment variables, you can use all the method a dict has. For instance, you could write :

os.environ.get('test_var', 'default_value')

edited Mar 1, 2019 at 12:55

Sergio Ivanuzzo

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answered May 29, 2018 at 8:30

0xdead

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2 Comments

Georgi Stoyanov Over a year ago

Thanks it works, but I think you can easily omit the , 'default_value' part. It works just fine with os.environ.get('test_var')

0xdead Over a year ago

It will also work if you use a simple dict lookup os.environ['test_var']. Use the get method with a default only when it make sense - when the value will not always exist in the environment variable.

Rishikesh Teke · Accepted Answer · 2018-05-29 08:35:56Z

7

Check python extension it should be .py instead of .sh 1.sh

#!/bin/bash
 test_var="Test Variable"
 export test_var
 echo "1.sh has been executed"
 python 2.py

os library will gave you the access the environment variable. Following python code will gave you the required result,

#!/usr/bin/env python3
import os
print("The python script has been invoked successfully")
print(os.environ['test_var'])

Check for reference : How do I access environment variables from Python?

answered May 29, 2018 at 8:35

Rishikesh Teke

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6 Comments

Georgi Stoyanov Over a year ago

I think here you need to put .get in your print statement, without it it doesn't work: print(os.environ.get['test_var'])

Rishikesh Teke Over a year ago

@GeorgеStoyanov I have executed above code on ubuntu and It worked without .get.

Georgi Stoyanov Over a year ago

if I execute it without the .get I get an error: AttributeError: _Environ instance has no __call__ method. I am also using Ubuntu 16.04.4 LTS.

Rishikesh Teke Over a year ago

If i execute with .get , get an error Traceback (most recent call last): File "2.py", line 4, in <module> print(os.environ.get['test_var']) TypeError: 'method' object is not subscriptable

Rishikesh Teke Over a year ago

ohh i got the mistake .get is the method so os.environ.get('test_var') works on my end and there is also alternative os.environ['test_var']

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