replace_in_nested_dict.py

def replace_in_nested_dict(dict_in, str_old, str_new):
    ''' loop over ALL levels of a dictionary, replacing str_old with str_new
        i am working with collections.OrderedDict(), which may be replaced with
        an ordinary dict. i have tested it with both.
    '''
    if not isinstance(dict_in, dict):
        raise TypeError('First argument has to be of type dict. Is type: ' + type(dict_in))
    if not isinstance(str_old, str):
        raise TypeError('Second argument has to be of type str. Is type: ' + type(str_old))
    if not isinstance(str_new, str):
        raise TypeError('Second argument has to be of type str. Is type: ' + type(str_new))
    dict_out = collections.OrderedDict()
    for key, value in dict_in.iteritems():
        # if the current value is a dict, we have to go through it, too
        if isinstance(value, dict):
            dict_out[key] = replace_in_nested_dict(value, str_old, str_new)
        elif isinstance(value, str) and (str_old in value):
            dict_out[key] = value.replace(str_old, str_new)
        else:
            dict_out[key] = value
    return dict_out