Concat Key Marker

Concat - Voluptuous.py

# -*- coding: utf-8 -*-
from voluptuous import Optional
from operator import is_not
from functools import partial


class Concat(object):
    """
    Creates a concatenated Optional Marker for voluptuous
    
    Example: 
    >>> from voluptuous import Schema
    >>> ENV = Concat(prefix="MOD_WSGI_")
    >>> schema = Schema({ENV('HOST', default='0.0.0.0'): str})
    >>> schema({})
    {'MOD_WSGI_HOST': '0.0.0.0'}
    """

    def __init__(self, prefix = None, suffix = None, **kwargs):
        self.separator = kwargs.pop('separator', "")
        self.marker = kwargs.pop('marker', Optional)
        self.prefix = prefix
        self.suffix = suffix

    def __call__(self, name, marker=None, *args, **kwargs):
        marker = marker or self.marker
        names = self.prefix, name, self.suffix
        names = list(filter(partial(is_not, None), names))
        name = self.separator.join(names)
        return marker(name , *args, **kwargs)