Value Types and Operators

A value type corresponds to the shape of the value key in a filter. It might be numeric (3), or string (Mad-Eye Moody) or relative_date (last_7_days). Each operator specifes the unique value type it operates on. Each data_source can list any number of value types it will support.

For example, “Order Date” source from our quickstart example lists that it supports both relative_date and absolute_date. The values for relative_date look like last_month or next_7_days. The values for absolute_date look like 2017-05-18T12:30. Because both absolute_ and relative_date value_types are supported for “Order Date”, we can use the relative_date operators (within and outside of) as well as the absolute_date operators (before and after).

The existing value types and operators can be easily extended by subclassing Winnow. We will see out to do this in Extending Winnow.


The numeric value type provides operators for >=, <=, >, <, is, and is not.

    'data_source': 'Number Scoops',
    'operator': '>=',
    'value': 3,


Data sources marked a supporting the string value type can use the is, is not, contains, starts with, more than __ words, and fewer than __ words operators.

    'data_source': "Scooper's Name",
    'operator': 'more than __ words',
    'value': 3,
    'data_source': "Scooper's Name",
    'operator': 'contains',
    'value': 'Heidi',


To use the collection operators, a data source will usually need to provide a list of picklist_options to the client. It’s fine to include those directly on the data source object:

    'display_name': 'Flavor',
    'column': 'flavor',
    'value_types': ['collection'],
    'picklist_options': [
        'Mint Chocolate Chip',
        'Cherry Garcia',
        'Cookie Dough',
        'Rocky Road',
        'Rainbow Sherbet',

Collections have access to any of and not any of operators.

    'data_source': 'Flavor',
    'operator': 'any of',
    'value': ['Strawberry', 'Chocolate'],

Datetime Operators

Datetime operators are broken down into two sets, relative and absolute. Most timestamp sources will want to support both.


Absolute date values are ISO8601 strings, like "2017-03-22T18:14:30". The supported operators are before and after.

    'data_source': 'Purchase Date',
    'operator': 'after',
    'value': '2017-03-22T18:14:30',


Relative date values are also strings, but they’re things like "last_30_days" and "current_month". I’m not very happy with how these are designed, so they will likely change in a future version. Please let me know if you have any advice. Maybe there’s already a standard way to refer to intervals of time that aren’t anchored to a particular day?

    'data_source': 'Purchase Date',
    'operator': 'within',
    'value': 'last_7_days',

The list of available values is found in