A way to validate keys that start with a given prefix.

StartsWith - Voluptuous.py

# -*- coding: utf-8 -*-
from voluptuous import Marker, Schema


class StartsWith(Marker):
    """
    A way to validate keys that start with a given prefix.

    Example:
        >>> from voluptuous.util import DefaultTo
        >>> from voluptuous import REMOVE_EXTRA, Any
        >>> test_dict = {
        ...     'MOD_WSGI_HOST': '0.0.0.0',
        ...     'MOD_WSGI_PORT': 80,
        ...     'META': 'Hello World!',
        ...     'LIMIT_REQUEST_BODY': 50
        ... }
        >>> schema = Schema({
        ...     StartsWith(starts_with='MOD_WSGI_'): Any(str, int)
        ... }, extra=REMOVE_EXTRA)
        >>> schema(test_dict)
        {'MOD_WSGI_HOST': '0.0.0.0', 'MOD_WSGI_PORT': 80}

        >>> schema = Schema({
        ...     StartsWith(starts_with='MOD_WSGI_'): Any(str, int),
        ...     'META': str
        ... }, extra=REMOVE_EXTRA)
        >>> schema(test_dict)
        {'MOD_WSGI_HOST': '0.0.0.0', 'MOD_WSGI_PORT': 80, 'META': 'Hello World!'}
    """

    def __init__(self, starts_with, msg=None):
        super().__init__(None, msg=msg)

        def starts(v):
            if v.startswith(starts_with):
                return v
            raise ValueError()

        self._schema = Schema(starts)