Python: get argument value in a decorator by name of the argument

wrapper_arg_value.py

import inspect
import functools
import Command

FORBIDDEN_SCHEMAS = {'public'}

def no_forbidden_schema(func):
    """Check if schema parameter is in FORBIDDEN_SCHEMAS."""
    @functools.wraps(func)
    def wrapper(self, *args, **kwargs):
        try:
            schema = kwargs['schema']
        except KeyError:
            schema_arg_index = inspect.getargspec(func).args.index('schema')
            schema = args[schema_arg_index]

        if schema in FORBIDDEN_SCHEMAS:
            return 'Error: Forbidden schema!'

        return func(self, *args, **kwargs)

    return wrapper


# Usage:
class AddTeam(Command):
    @no_forbidden_schema
    def run(self, name, schema, domain):
        pass
        
# or:
class AddTeam(Command):
    @no_forbidden_schema
    def run(self, schema, name, domain):
        pass

# or:
class AddTeam(Command):
    @no_forbidden_schema
    def run(self, name, schema='guest', domain="example.com"):
        pass