error_dict.py

from collections import defaultdict
import logging

class ErrorDict(defaultdict):
    """
    Stores a list of errors per host, when initialized with a list.

    >>> ed = ErrorDict()
    >>> ed['google.com'].append('first')
    >>> ed['google.com'].append('another error')
    >>> ed['fark.com'].append('errorz')
    >>> for host, error_list in ed.iteritems():
    ...   print "%s" % host
    ...   print '\n'.join(["\t%s" % (error) for error in error_list])
    ...
    google.com
        first
        another error
    fark.com
        errorz
    >>>
    """
    def __init__(self, *args, **kwargs):
        """
        Override the defaultfactory arg (original arg) as ErrorDict
        should always have lists.
        """
        super(ErrorDict, self).__init__(list, **kwargs)

    def __setitem__(self, host, error):
        logging.info('%s had an error: %s' % (host, error))
        super(ErrorDict, self).__setitem__(host, error)

    def pretty_print(self):
        for key, val_list in self.iteritems():
            print '%s' % key
            print '\n'.join(['\t%s' % (val) for val in val_list])