A Python function that does multiple string replace ops in a single pass.

replace.py

import re

def replace(string, substitutions):

    substrings = sorted(substitutions, key=len, reverse=True)
    regex = re.compile('|'.join(map(re.escape, substrings)))
    return regex.sub(lambda match: substitutions[match.group(0)], string)

You have your point of view, and I have my...
The principles of code readability are important to me.
I try to use lambda functions as little as possible, because they degrade performance and do not support typing.
In addition, I prefer to immediately make the functionality more flexible for adding new features in the future. It seems to me that it is more convenient to add a new methods or protocols than to rewrite everything.
I myself don't really like to use OOP unnecessarily, but I think the principle of encapsulation (in methods for example) is the most important.

PS: I only suggested my version, including your solution. With hope that this will help someone, according to OpenSource spirit.
I'm not attacking your programming principles =)