# JoinFilter **`class JoinFilter(config)`** Bases: [`Filter`](squirro.lib.nlp.steps.filters.Filter.md#squirro.lib.nlp.steps.filters.Filter) The join [`Filter`](squirro.lib.nlp.steps.filters.Filter.md#squirro.lib.nlp.steps.filters.Filter) joins a list to a string **Input** - the input field needs to be of type [`list`](https://docs.python.org/3.11/library/stdtypes.html#list) [ [`str`](https://docs.python.org/3.11/library/stdtypes.html#str) ]. **Output** - 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)) – join - `input_field` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)) – Field to join - `output_field` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)) – Field to join into - `delimiter` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``'``,``'`) – Delimiter to join on **Example** ```json { "step": "filter", "type": "join", "input_field":"sentences", "output_field":"text", "delimiter":". " } ``` Methods SummaryMethods 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)