How to access environment variable values?

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How to access environment variable values?

I set an environment variable that I want to access in my Python application. How do I get its value?

Answer #1:

Environment variables are accessed through os.environ

import os
print(os.environ['HOME'])

Or you can see a list of all the environment variables using:

os.environ

As sometimes you might need to see a complete list!

# using get will return `None` if a key is not present rather than raise a `KeyError`
print(os.environ.get('KEY_THAT_MIGHT_EXIST'))
# os.getenv is equivalent, and can also give a default value instead of `None`
print(os.getenv('KEY_THAT_MIGHT_EXIST', default_value))

Python default installation on Windows is C:Python. If you want to find out while running python you can do:

import sys
print(sys.prefix)
Answered By: Rod

Answer #2:

To check if the key exists (returns True or False)

'HOME' in os.environ

You can also use get() when printing the key; useful if you want to use a default.

print(os.environ.get('HOME', '/home/username/'))

where /home/username/ is the default

Answered By: lgriffiths

Answer #3:

The original question (first part) was “how to check environment variables in Python.”

Here’s how to check if $FOO is set:

try:
   os.environ["FOO"]
except KeyError:
   print "Please set the environment variable FOO"
   sys.exit(1)
Answered By: Scott C Wilson

Answer #4:

You can access to the environment variables using

import os
print os.environ

Try to see the content of PYTHONPATH or PYTHONHOME environment variables, maybe this will be helpful for your second question. However you should clarify it.

Answered By: andrei1089

Answer #5:

Actually it can be done this away:

import os
for item, value in os.environ.items():
    print('{}: {}'.format(item, value))

Or simply:

for i, j in os.environ.items():
    print(i, j)

For view the value in the parameter:

print(os.environ['HOME'])

Or:

print(os.environ.get('HOME'))

To set the value:

os.environ['HOME'] = '/new/value'
Answered By: britodfbr

Answer #6:

As for the environment variables:

import os
print os.environ["HOME"]

I’m afraid you’d have to flesh out your second point a little bit more before a decent answer is possible.

Answered By: Jim Brissom

Answer #7:

import os
for a in os.environ:
    print('Var: ', a, 'Value: ', os.getenv(a))
print("all done")

That will print all of the environment variables along with their values.

Answered By: Azorian

Answer #8:

If you are planning to use the code in a production web application code,
using any web framework like Django/Flask, use projects like envparse, using it you can read the value as your defined type.

from envparse import env
# will read WHITE_LIST=hello,world,hi to white_list = ["hello", "world", "hi"]
white_list = env.list("WHITE_LIST", default=[])
# Perfect for reading boolean
DEBUG = env.bool("DEBUG", default=False)

NOTE: kennethreitz’s autoenv is a recommended tool for making project specific environment variables, please note that those who are using autoenv please keep the .env file private (inaccessible to public)

Answered By: Renjith Thankachan

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