Jinja

$ export MYENVVAR=foo

$ nano example.py

from jinja2 import Template, StrictUndefined
import os
template = Template("Hello {{ env['MYENVVAR'] or 'DefaultVal' }}", undefined=StrictUndefined)
r = template.render(env=os.environ, name='somethingelse')
print(r)

Run template

$ python3 example.py

https://jinja.palletsprojects.com/en/2.11.x/intro/

Other Methods

targs = {}
targs['MYENVVAR'] = os.getenv('MYENVVAR')


with open('configMap.yml.jinja') as f_:
    template = Template(f_.read(), undefined=StrictUndefined)
txt = template.render(targs)
with open('configMap.yml', 'w') as f_:
    f_.write(txt)