Reading in environment variables from an environme

问题:

I'd like to run in a local environment a Python script which is normally run in a Docker container. The docker-compose.yml specifies an env_file which looks (partially) like the following:

DB_ADDR=rethinkdb
DB_PORT=28015
DB_NAME=ipercron

In order to run this locally, I would like these lines to be converted to

os.environ['DB_ADDR'] = 'rethinkdb'
os.environ['DB_PORT'] = '28015'
os.environ['DB_NAME'] = 'ipercron'

I could write my parser, but I was wondering if there are any existing modules/tools to read in environment variables from configuration files?

回答1:

You can use ConfigParser. Sample example can be found here.

But this library expects your key=value data to be present under some [heading]. For example, like:

[mysqld]
user = mysql  # Key with values
pid-file = /var/run/mysqld/mysqld.pid
skip-external-locking
old_passwords = 1
skip-bdb      # Key without value
skip-innodb

回答2:

This could also work for you:

env_vars = []
with open(env_file) as f:
    for line in f:
        if line.startswith('#') or not line.strip():
            continue
        # if 'export' not in line:
        #     continue
        # Remove leading `export `, if you have those
        # then, split name / value pair
        # key, value = line.replace('export ', '', 1).strip().split('=', 1)
        key, value = line.strip().split('=', 1)
        # os.environ[key] = value  # Load to local environ
        env_vars.append({'name': key, 'value': value}) # Save to a list

print(env_vars);

In the comments you'll find a few different ways to save the env vars and also a few parsing options i.e. to get rid of leading export keyword. Another way would be to use the python-dotenv library. Cheers.

回答3:

Using only python std

import re

envre = re.compile(r'''^([^\s=]+)=(?:[\s"']*)(.+?)(?:[\s"']*)$''')
result = {}
with open('/etc/os-release') as ins:
    for line in ins:
        match = envre.match(line)
        if match is not None:
            result[match.group(1)] = match.group(2)

回答4:

I will use https://pypi.org/project/python-dotenv/ just type pip install python-dotenv and then in your code you can use

from dotenv import load_dotenv
load_dotenv()

this is the way i do when i need to test code outside my docker system, and prepare it to return it into docker again.

回答5:

How about this for a more compact solution:

import os

with open('.docker-compose-env', 'r') as fh:
    vars_dict = dict(
        tuple(line.split('='))
        for line in fh.readlines() if not line.startswith('#')
    )

print(vars_dict)
os.environ.update(vars_dict)