Python: Common prefix of pathlib.Path

common_prefix.py

import collections
import pathlib

def common_prefix(*paths):
    """Common prefix of given paths"""
    counter = collections.Counter()

    for path in paths:
        assert isinstance(path, pathlib.Path)
        counter.update([path])
        counter.update(path.parents)

    try:
        return sorted((x for x, count in counter.items() if count >= len(paths)), key=lambda x: len(str(x)))[-1]
    except LookupError as e:
        raise ValueError('No common prefix found') from e