id,page,ref,title,content,breadcrumbs,references
writing_plugins:writing-plugins-one-off,writing_plugins,writing-plugins-one-off,Writing one-off plugins,"The quickest way to start writing a plugin is to create a  my_plugin.py  file and drop it into your  plugins/  directory. Here is an example plugin, which adds a new custom SQL function called  hello_world()  which takes no arguments and returns the string  Hello world! . 
             from datasette import hookimpl


@hookimpl
def prepare_connection(conn):
    conn.create_function(
        ""hello_world"", 0, lambda: ""Hello world!""
    ) 
             If you save this in  plugins/my_plugin.py  you can then start Datasette like this: 
             datasette serve mydb.db --plugins-dir=plugins/ 
             Now you can navigate to  http://localhost:8001/mydb  and run this SQL: 
             select hello_world(); 
             To see the output of your plugin.","[""Writing plugins""]","[{""href"": ""http://localhost:8001/mydb"", ""label"": ""http://localhost:8001/mydb""}]"