# RegexFilter **`class RegexFilter(config)`** Bases: [`Filter`](squirro.lib.nlp.steps.filters.Filter.md#squirro.lib.nlp.steps.filters.Filter) The regex [`Filter`](squirro.lib.nlp.steps.filters.Filter.md#squirro.lib.nlp.steps.filters.Filter) filters documents based on a supplied list of blacklist and whitelist regexes **Input** - all input fields needs to be of type [`str`](https://docs.python.org/3.11/library/stdtypes.html#str). **Output** - (optional) the output field is filled with data of type [`str`](https://docs.python.org/3.11/library/stdtypes.html#str). Parameters - `type` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)) – regex - `blacklist_regexes` ([`list`](https://docs.python.org/3.11/library/stdtypes.html#list)`, ``[``]`) – List of blacklist regexes to apply - `fields` ([`list`](https://docs.python.org/3.11/library/stdtypes.html#list)) – Fields to apply regexes - `output_field` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``None`) – Field to record if regex matches - `matching_label` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``'match'`) – Label given if regex matches - `non_matching_label` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``'no_match'`) – Label given if regex does not match - `whitelist_regexes` ([`list`](https://docs.python.org/3.11/library/stdtypes.html#list)`, ``[``]`) – List of whitelist regexes to apply - `rule_field` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``None`) – Field to record the rule which triggered the match (manly used in the context of proximity filters) - `no_rule_matched_label` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``'NO_RULE_MATCHED'`) – Rule given if regex does not match (manly used in the context of proximity filters) - `default_language` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``'en'`) – Default language if language_field is not present. - `language_field` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``'language'`) – Document field that gives the language. **Example** ```json { "step": "filter", "type": "regex", "fields": ["body"], "mark_as_skipped": true, "whitelist_regexes": ["^.{20,}$"] } ``` Attributes SummaryMethods SummaryAttributes Documentation **`REG_FLAGS = 0`** Methods Documentation **`process_doc(doc)`** Process a document Parameters `doc` ([`Document`](../technical/libnlp/base.md#squirro.lib.nlp.document.Document)) – Document Returns Processed document Return type [Document](../technical/libnlp/base.md#squirro.lib.nlp.document.Document)