Use Python's Built-In Template Strings To Generate Output

Python ships with built-in functionality for generating output from templates that provide basic variable replacement.

From A String

from string import Template

skeleton = Template('Name: $name - Color: $color')

output = skeleton.substitute(
            name="Karl", 
            color="Green"
        )

print(output)

Produces:

Name: Karl - Color: Green

From A File

Assuming you have a files named template.txt with:

this is the name: $name
and the color: $color

Then this:

from string import Template

with open('template.txt') as _tmpl:
	frame = Template(_tmpl.read())
	output = frame.substitute(
	   name="Karl",
	   color="Green"
    )
	print(output)

Will produce:

this is the name: Karl
and the color: Green

Reference

docs: https://docs.python.org/3/library/string.html#template-strings