id,page,ref,title,content,breadcrumbs,references internals:datasette-render-template,internals,datasette-render-template,"await .render_template(template, context=None, request=None)","template - string, list of strings or jinja2.Template The template file to be rendered, e.g. my_plugin.html . Datasette will search for this file first in the --template-dir= location, if it was specified - then in the plugin's bundled templates and finally in Datasette's set of default templates. If this is a list of template file names then the first one that exists will be loaded and rendered. If this is a Jinja Template object it will be used directly. context - None or a Python dictionary The context variables to pass to the template. request - request object or None If you pass a Datasette request object here it will be made available to the template. Renders a Jinja template using Datasette's preconfigured instance of Jinja and returns the resulting string. The template will have access to Datasette's default template functions and any functions that have been made available by other plugins.","[""Internals for plugins"", ""Datasette class""]","[{""href"": ""https://jinja.palletsprojects.com/en/2.11.x/api/#jinja2.Template"", ""label"": ""Template object""}, {""href"": ""https://jinja.palletsprojects.com/en/2.11.x/"", ""label"": ""Jinja template""}]" internals:datasette-resolve-database,internals,datasette-resolve-database,.resolve_database(request),"request - Request object A request object If you are implementing your own custom views, you may need to resolve the database that the user is requesting based on a URL path. If the regular expression for your route declares a database named group, you can use this method to resolve the database object. This returns a Database instance. If the database cannot be found, it raises a datasette.utils.asgi.DatabaseNotFound exception - which is a subclass of datasette.utils.asgi.NotFound with a .database_name attribute set to the name of the database that was requested.","[""Internals for plugins"", ""Datasette class""]",[] internals:datasette-resolve-row,internals,datasette-resolve-row,.resolve_row(request),"request - Request object A request object This method assumes your route declares named groups for database , table and pks . It returns a ResolvedRow named tuple instance with the following fields: db - Database The database object table - string The name of the table sql - string SQL snippet that can be used in a WHERE clause to select the row params - dict Parameters that should be passed to the SQL query pks - list List of primary key column names pk_values - list List of primary key values decoded from the URL row - sqlite3.Row The row itself If the database or table cannot be found it raises a datasette.utils.asgi.DatabaseNotFound exception. If the table does not exist it raises a datasette.utils.asgi.TableNotFound exception. If the row cannot be found it raises a datasette.utils.asgi.RowNotFound exception. This has .database_name , .table and .pk_values attributes, extracted from the request path.","[""Internals for plugins"", ""Datasette class""]",[] internals:datasette-resolve-table,internals,datasette-resolve-table,.resolve_table(request),"request - Request object A request object This assumes that the regular expression for your route declares both a database and a table named group. It returns a ResolvedTable named tuple instance with the following fields: db - Database The database object table - string The name of the table (or view) is_view - boolean True if this is a view, False if it is a table If the database or table cannot be found it raises a datasette.utils.asgi.DatabaseNotFound exception. If the table does not exist it raises a datasette.utils.asgi.TableNotFound exception - a subclass of datasette.utils.asgi.NotFound with .database_name and .table attributes.","[""Internals for plugins"", ""Datasette class""]",[] internals:datasette-setting,internals,datasette-setting,.setting(key),"key - string The name of the setting, e.g. base_url . Returns the configured value for the specified setting . This can be a string, boolean or integer depending on the requested setting. For example: downloads_are_allowed = datasette.setting(""allow_download"")","[""Internals for plugins"", ""Datasette class""]",[] internals:datasette-sign,internals,datasette-sign,".sign(value, namespace=""default"")","value - any serializable type The value to be signed. namespace - string, optional An alternative namespace, see the itsdangerous salt documentation . Utility method for signing values, such that you can safely pass data to and from an untrusted environment. This is a wrapper around the itsdangerous library. This method returns a signed string, which can be decoded and verified using .unsign(value, namespace=""default"") .","[""Internals for plugins"", ""Datasette class""]","[{""href"": ""https://itsdangerous.palletsprojects.com/en/1.1.x/serializer/#the-salt"", ""label"": ""itsdangerous salt documentation""}, {""href"": ""https://itsdangerous.palletsprojects.com/"", ""label"": ""itsdangerous""}]" internals:datasette-track-event,internals,datasette-track-event,await .track_event(event),"event - Event An instance of a subclass of datasette.events.Event . Plugins can call this to track events, using classes they have previously registered. See Event tracking for details. The event will then be passed to all plugins that have registered to receive events using the track_event(datasette, event) hook. Example usage, assuming the plugin has previously registered the BanUserEvent class: await datasette.track_event( BanUserEvent(user={""id"": 1, ""username"": ""cleverbot""}) )","[""Internals for plugins"", ""Datasette class""]",[] internals:datasette-unsign,internals,datasette-unsign,".unsign(value, namespace=""default"")","signed - any serializable type The signed string that was created using .sign(value, namespace=""default"") . namespace - string, optional The alternative namespace, if one was used. Returns the original, decoded object that was passed to .sign(value, namespace=""default"") . If the signature is not valid this raises a itsdangerous.BadSignature exception.","[""Internals for plugins"", ""Datasette class""]",[] internals:id1,internals,id1,.get_internal_database(),Returns a database object for reading and writing to the private internal database .,"[""Internals for plugins"", ""Datasette class""]",[] internals:internals-csrf,internals,internals-csrf,CSRF protection,"Datasette uses asgi-csrf to guard against CSRF attacks on form POST submissions. Users receive a ds_csrftoken cookie which is compared against the csrftoken form field (or x-csrftoken HTTP header) for every incoming request. If your plugin implements a
anywhere you will need to include that token. You can do so with the following template snippet: If you are rendering templates using the await .render_template(template, context=None, request=None) method the csrftoken() helper will only work if you provide the request= argument to that method. If you forget to do this you will see the following error: form-urlencoded POST field did not match cookie You can selectively disable CSRF protection using the skip_csrf(datasette, scope) hook.","[""Internals for plugins""]","[{""href"": ""https://github.com/simonw/asgi-csrf"", ""label"": ""asgi-csrf""}]" internals:internals-database,internals,internals-database,Database class,"Instances of the Database class can be used to execute queries against attached SQLite databases, and to run introspection against their schemas.","[""Internals for plugins""]",[] internals:internals-database-introspection,internals,internals-database-introspection,Database introspection,"The Database class also provides properties and methods for introspecting the database. db.name - string The name of the database - usually the filename without the .db prefix. db.size - integer The size of the database file in bytes. 0 for :memory: databases. db.mtime_ns - integer or None The last modification time of the database file in nanoseconds since the epoch. None for :memory: databases. db.is_mutable - boolean Is this database mutable, and allowed to accept writes? db.is_memory - boolean Is this database an in-memory database? await db.attached_databases() - list of named tuples Returns a list of additional databases that have been connected to this database using the SQLite ATTACH command. Each named tuple has fields seq , name and file . await db.table_exists(table) - boolean Check if a table called table exists. await db.view_exists(view) - boolean Check if a view called view exists. await db.table_names() - list of strings List of names of tables in the database. await db.view_names() - list of strings List of names of views in the database. await db.table_columns(table) - list of strings Names of columns in a specific table. await db.table_column_details(table) - list of named tuples Full details of the columns in a specific table. Each column is represented by a Column named tuple with fields cid (integer representing the column position), name (string), type (string, e.g. REAL or VARCHAR(30) ), notnull (integer 1 or 0), default_value (string or None), is_pk (integer 1 or 0). await db.primary_keys(table) - list of strings Names of the columns that are part of the primary key for this table. await db.fts_table(table) - string or None The name of the FTS table associated with this table, if one exists. await db.label_column_for_table(table) - string or None The label column that is associated with this table - either automatically detected or using the ""label_column"" key from Metadata , see Specifying the label column for a table . await db.foreign_keys_for_table(table) - list of dictionaries Details of columns in this table which are foreign keys to other tables. A list of dictionaries where each dictionary is shaped like this: {""column"": string, ""other_table"": string, ""other_column"": string} . await db.hidden_table_names() - list of strings List of tables which Datasette ""hides"" by default - usually these are tables associated with SQLite's full-text search feature, the SpatiaLite extension or tables hidden using the Hiding tables feature. await db.get_table_definition(table) - string Returns the SQL definition for the table - the CREATE TABLE statement and any associated CREATE INDEX statements. await db.get_view_definition(view) - string Returns the SQL definition of the named view. await db.get_all_foreign_keys() - dictionary Dictionary representing both incoming and outgoing foreign keys for this table. It has two keys, ""incoming"" and ""outgoing"" , each of which is a list of dictionaries with keys ""column"" , ""other_table"" and ""other_column"" . For example: { ""incoming"": [], ""outgoing"": [ { ""other_table"": ""attraction_characteristic"", ""column"": ""characteristic_id"", ""other_column"": ""pk"", }, { ""other_table"": ""roadside_attractions"", ""column"": ""attraction_id"", ""other_column"": ""pk"", } ] }","[""Internals for plugins"", ""Database class""]",[] internals:internals-datasette,internals,internals-datasette,Datasette class,"This object is an instance of the Datasette class, passed to many plugin hooks as an argument called datasette . You can create your own instance of this - for example to help write tests for a plugin - like so: from datasette.app import Datasette # With no arguments a single in-memory database will be attached datasette = Datasette() # The files= argument can load files from disk datasette = Datasette(files=[""/path/to/my-database.db""]) # Pass metadata as a JSON dictionary like this datasette = Datasette( files=[""/path/to/my-database.db""], metadata={ ""databases"": { ""my-database"": { ""description"": ""This is my database"" } } }, ) Constructor parameters include: files=[...] - a list of database files to open immutables=[...] - a list of database files to open in immutable mode metadata={...} - a dictionary of Metadata config_dir=... - the configuration directory to use, stored in datasette.config_dir","[""Internals for plugins""]",[] internals:internals-datasette-client,internals,internals-datasette-client,datasette.client,"Plugins can make internal simulated HTTP requests to the Datasette instance within which they are running. This ensures that all of Datasette's external JSON APIs are also available to plugins, while avoiding the overhead of making an external HTTP call to access those APIs. The datasette.client object is a wrapper around the HTTPX Python library , providing an async-friendly API that is similar to the widely used Requests library . It offers the following methods: await datasette.client.get(path, **kwargs) - returns HTTPX Response Execute an internal GET request against that path. await datasette.client.post(path, **kwargs) - returns HTTPX Response Execute an internal POST request. Use data={""name"": ""value""} to pass form parameters. await datasette.client.options(path, **kwargs) - returns HTTPX Response Execute an internal OPTIONS request. await datasette.client.head(path, **kwargs) - returns HTTPX Response Execute an internal HEAD request. await datasette.client.put(path, **kwargs) - returns HTTPX Response Execute an internal PUT request. await datasette.client.patch(path, **kwargs) - returns HTTPX Response Execute an internal PATCH request. await datasette.client.delete(path, **kwargs) - returns HTTPX Response Execute an internal DELETE request. await datasette.client.request(method, path, **kwargs) - returns HTTPX Response Execute an internal request with the given HTTP method against that path. These methods can be used with datasette.urls - for example: table_json = ( await datasette.client.get( datasette.urls.table( ""fixtures"", ""facetable"", format=""json"" ) ) ).json() datasette.client methods automatically take the current base_url setting into account, whether or not you use the datasette.urls family of methods to construct the path. For documentation on available **kwargs options and the shape of the HTTPX Response object refer to the HTTPX Async documentation .","[""Internals for plugins"", ""Datasette class""]","[{""href"": ""https://www.python-httpx.org/"", ""label"": ""HTTPX Python library""}, {""href"": ""https://requests.readthedocs.io/"", ""label"": ""Requests library""}, {""href"": ""https://www.python-httpx.org/async/"", ""label"": ""HTTPX Async documentation""}]" internals:internals-datasette-urls,internals,internals-datasette-urls,datasette.urls,"The datasette.urls object contains methods for building URLs to pages within Datasette. Plugins should use this to link to pages, since these methods take into account any base_url configuration setting that might be in effect. datasette.urls.instance(format=None) Returns the URL to the Datasette instance root page. This is usually ""/"" . datasette.urls.path(path, format=None) Takes a path and returns the full path, taking base_url into account. For example, datasette.urls.path(""-/logout"") will return the path to the logout page, which will be ""/-/logout"" by default or /prefix-path/-/logout if base_url is set to /prefix-path/ datasette.urls.logout() Returns the URL to the logout page, usually ""/-/logout"" datasette.urls.static(path) Returns the URL of one of Datasette's default static assets, for example ""/-/static/app.css"" datasette.urls.static_plugins(plugin_name, path) Returns the URL of one of the static assets belonging to a plugin. datasette.urls.static_plugins(""datasette_cluster_map"", ""datasette-cluster-map.js"") would return ""/-/static-plugins/datasette_cluster_map/datasette-cluster-map.js"" datasette.urls.static(path) Returns the URL of one of Datasette's default static assets, for example ""/-/static/app.css"" datasette.urls.database(database_name, format=None) Returns the URL to a database page, for example ""/fixtures"" datasette.urls.table(database_name, table_name, format=None) Returns the URL to a table page, for example ""/fixtures/facetable"" datasette.urls.query(database_name, query_name, format=None) Returns the URL to a query page, for example ""/fixtures/pragma_cache_size"" These functions can be accessed via the {{ urls }} object in Datasette templates, for example: Homepage Fixtures database facetable table pragma_cache_size query Use the format=""json"" (or ""csv"" or other formats supported by plugins) arguments to get back URLs to the JSON representation. This is the path with .json added on the end. These methods each return a datasette.utils.PrefixedUrlString object, which is a subclass of the Python str type. This allows the logic that considers the base_url setting to detect if that prefix has already been applied to the path.","[""Internals for plugins"", ""Datasette class""]",[] internals:internals-internal,internals,internals-internal,Datasette's internal database,"Datasette maintains an ""internal"" SQLite database used for configuration, caching, and storage. Plugins can store configuration, settings, and other data inside this database. By default, Datasette will use a temporary in-memory SQLite database as the internal database, which is created at startup and destroyed at shutdown. Users of Datasette can optionally pass in a --internal flag to specify the path to a SQLite database to use as the internal database, which will persist internal data across Datasette instances. Datasette maintains tables called catalog_databases , catalog_tables , catalog_columns , catalog_indexes , catalog_foreign_keys with details of the attached databases and their schemas. These tables should not be considered a stable API - they may change between Datasette releases. The internal database is not exposed in the Datasette application by default, which means private data can safely be stored without worry of accidentally leaking information through the default Datasette interface and API. However, other plugins do have full read and write access to the internal database. Plugins can access this database by calling internal_db = datasette.get_internal_database() and then executing queries using the Database API . Plugin authors are asked to practice good etiquette when using the internal database, as all plugins use the same database to store data. For example: Use a unique prefix when creating tables, indices, and triggers in the internal database. If your plugin is called datasette-xyz , then prefix names with datasette_xyz_* . Avoid long-running write statements that may stall or block other plugins that are trying to write at the same time. Use temporary tables or shared in-memory attached databases when possible. Avoid implementing features that could expose private data stored in the internal database by other plugins.","[""Internals for plugins""]",[] internals:internals-multiparams,internals,internals-multiparams,The MultiParams class,"request.args is a MultiParams object - a dictionary-like object which provides access to query string parameters that may have multiple values. Consider the query string ?foo=1&foo=2&bar=3 - with two values for foo and one value for bar . request.args[key] - string Returns the first value for that key, or raises a KeyError if the key is missing. For the above example request.args[""foo""] would return ""1"" . request.args.get(key) - string or None Returns the first value for that key, or None if the key is missing. Pass a second argument to specify a different default, e.g. q = request.args.get(""q"", """") . request.args.getlist(key) - list of strings Returns the list of strings for that key. request.args.getlist(""foo"") would return [""1"", ""2""] in the above example. request.args.getlist(""bar"") would return [""3""] . If the key is missing an empty list will be returned. request.args.keys() - list of strings Returns the list of available keys - for the example this would be [""foo"", ""bar""] . key in request.args - True or False You can use if key in request.args to check if a key is present. for key in request.args - iterator This lets you loop through every available key. len(request.args) - integer Returns the number of keys.","[""Internals for plugins""]",[] internals:internals-request,internals,internals-request,Request object,"The request object is passed to various plugin hooks. It represents an incoming HTTP request. It has the following properties: .scope - dictionary The ASGI scope that was used to construct this request, described in the ASGI HTTP connection scope specification. .method - string The HTTP method for this request, usually GET or POST . .url - string The full URL for this request, e.g. https://latest.datasette.io/fixtures . .scheme - string The request scheme - usually https or http . .headers - dictionary (str -> str) A dictionary of incoming HTTP request headers. Header names have been converted to lowercase. .cookies - dictionary (str -> str) A dictionary of incoming cookies .host - string The host header from the incoming request, e.g. latest.datasette.io or localhost . .path - string The path of the request excluding the query string, e.g. /fixtures . .full_path - string The path of the request including the query string if one is present, e.g. /fixtures?sql=select+sqlite_version() . .query_string - string The query string component of the request, without the ? - e.g. name__contains=sam&age__gt=10 . .args - MultiParams An object representing the parsed query string parameters, see below. .url_vars - dictionary (str -> str) Variables extracted from the URL path, if that path was defined using a regular expression. See register_routes(datasette) . .actor - dictionary (str -> Any) or None The currently authenticated actor (see actors ), or None if the request is unauthenticated. The object also has two awaitable methods: await request.post_vars() - dictionary Returns a dictionary of form variables that were submitted in the request body via POST . Don't forget to read about CSRF protection ! await request.post_body() - bytes Returns the un-parsed body of a request submitted by POST - useful for things like incoming JSON data. And a class method that can be used to create fake request objects for use in tests: fake(path_with_query_string, method=""GET"", scheme=""http"", url_vars=None) Returns a Request instance for the specified path and method. For example: from datasette import Request from pprint import pprint request = Request.fake( ""/fixtures/facetable/"", url_vars={""database"": ""fixtures"", ""table"": ""facetable""}, ) pprint(request.scope) This outputs: {'http_version': '1.1', 'method': 'GET', 'path': '/fixtures/facetable/', 'query_string': b'', 'raw_path': b'/fixtures/facetable/', 'scheme': 'http', 'type': 'http', 'url_route': {'kwargs': {'database': 'fixtures', 'table': 'facetable'}}}","[""Internals for plugins""]","[{""href"": ""https://asgi.readthedocs.io/en/latest/specs/www.html#connection-scope"", ""label"": ""ASGI HTTP connection scope""}]" internals:internals-response,internals,internals-response,Response class,"The Response class can be returned from view functions that have been registered using the register_routes(datasette) hook. The Response() constructor takes the following arguments: body - string The body of the response. status - integer (optional) The HTTP status - defaults to 200. headers - dictionary (optional) A dictionary of extra HTTP headers, e.g. {""x-hello"": ""world""} . content_type - string (optional) The content-type for the response. Defaults to text/plain . For example: from datasette.utils.asgi import Response response = Response( ""This is XML"", content_type=""application/xml; charset=utf-8"", ) The quickest way to create responses is using the Response.text(...) , Response.html(...) , Response.json(...) or Response.redirect(...) helper methods: from datasette.utils.asgi import Response html_response = Response.html(""This is HTML"") json_response = Response.json({""this_is"": ""json""}) text_response = Response.text( ""This will become utf-8 encoded text"" ) # Redirects are served as 302, unless you pass status=301: redirect_response = Response.redirect( ""https://latest.datasette.io/"" ) Each of these responses will use the correct corresponding content-type - text/html; charset=utf-8 , application/json; charset=utf-8 or text/plain; charset=utf-8 respectively. Each of the helper methods take optional status= and headers= arguments, documented above.","[""Internals for plugins""]",[] internals:internals-response-asgi-send,internals,internals-response-asgi-send,Returning a response with .asgi_send(send),"In most cases you will return Response objects from your own view functions. You can also use a Response instance to respond at a lower level via ASGI, for example if you are writing code that uses the asgi_wrapper(datasette) hook. Create a Response object and then use await response.asgi_send(send) , passing the ASGI send function. For example: async def require_authorization(scope, receive, send): response = Response.text( ""401 Authorization Required"", headers={ ""www-authenticate"": 'Basic realm=""Datasette"", charset=""UTF-8""' }, status=401, ) await response.asgi_send(send)","[""Internals for plugins"", ""Response class""]",[] internals:internals-response-set-cookie,internals,internals-response-set-cookie,Setting cookies with response.set_cookie(),"To set cookies on the response, use the response.set_cookie(...) method. The method signature looks like this: def set_cookie( self, key, value="""", max_age=None, expires=None, path=""/"", domain=None, secure=False, httponly=False, samesite=""lax"", ): ... You can use this with datasette.sign() to set signed cookies. Here's how you would set the ds_actor cookie for use with Datasette authentication : response = Response.redirect(""/"") response.set_cookie( ""ds_actor"", datasette.sign({""a"": {""id"": ""cleopaws""}}, ""actor""), ) return response","[""Internals for plugins"", ""Response class""]",[] internals:internals-shortcuts,internals,internals-shortcuts,Import shortcuts,"The following commonly used symbols can be imported directly from the datasette module: from datasette import Response from datasette import Forbidden from datasette import NotFound from datasette import hookimpl from datasette import actor_matches_allow","[""Internals for plugins""]",[] internals:internals-tilde-encoding,internals,internals-tilde-encoding,Tilde encoding,"Datasette uses a custom encoding scheme in some places, called tilde encoding . This is primarily used for table names and row primary keys, to avoid any confusion between / characters in those values and the Datasette URLs that reference them. Tilde encoding uses the same algorithm as URL percent-encoding , but with the ~ tilde character used in place of % . Any character other than ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz0123456789_- will be replaced by the numeric equivalent preceded by a tilde. For example: / becomes ~2F . becomes ~2E % becomes ~25 ~ becomes ~7E Space becomes + polls/2022.primary becomes polls~2F2022~2Eprimary Note that the space character is a special case: it will be replaced with a + symbol. datasette.utils. tilde_encode s : str str Returns tilde-encoded string - for example /foo/bar -> ~2Ffoo~2Fbar datasette.utils. tilde_decode s : str str Decodes a tilde-encoded string, so ~2Ffoo~2Fbar -> /foo/bar","[""Internals for plugins"", ""The datasette.utils module""]","[{""href"": ""https://developer.mozilla.org/en-US/docs/Glossary/percent-encoding"", ""label"": ""URL percent-encoding""}]" internals:internals-tracer,internals,internals-tracer,datasette.tracer,"Running Datasette with --setting trace_debug 1 enables trace debug output, which can then be viewed by adding ?_trace=1 to the query string for any page. You can see an example of this at the bottom of latest.datasette.io/fixtures/facetable?_trace=1 . The JSON output shows full details of every SQL query that was executed to generate the page. The datasette-pretty-traces plugin can be installed to provide a more readable display of this information. You can see a demo of that here . You can add your own custom traces to the JSON output using the trace() context manager. This takes a string that identifies the type of trace being recorded, and records any keyword arguments as additional JSON keys on the resulting trace object. The start and end time, duration and a traceback of where the trace was executed will be automatically attached to the JSON object. This example uses trace to record the start, end and duration of any HTTP GET requests made using the function: from datasette.tracer import trace import httpx async def fetch_url(url): with trace(""fetch-url"", url=url): async with httpx.AsyncClient() as client: return await client.get(url)","[""Internals for plugins""]","[{""href"": ""https://latest.datasette.io/fixtures/facetable?_trace=1"", ""label"": ""latest.datasette.io/fixtures/facetable?_trace=1""}, {""href"": ""https://datasette.io/plugins/datasette-pretty-traces"", ""label"": ""datasette-pretty-traces""}, {""href"": ""https://latest-with-plugins.datasette.io/github/commits?_trace=1"", ""label"": ""a demo of that here""}]" internals:internals-tracer-trace-child-tasks,internals,internals-tracer-trace-child-tasks,Tracing child tasks,"If your code uses a mechanism such as asyncio.gather() to execute code in additional tasks you may find that some of the traces are missing from the display. You can use the trace_child_tasks() context manager to ensure these child tasks are correctly handled. from datasette import tracer with tracer.trace_child_tasks(): results = await asyncio.gather( # ... async tasks here ) This example uses the register_routes() plugin hook to add a page at /parallel-queries which executes two SQL queries in parallel using asyncio.gather() and returns their results. from datasette import hookimpl from datasette import tracer @hookimpl def register_routes(): async def parallel_queries(datasette): db = datasette.get_database() with tracer.trace_child_tasks(): one, two = await asyncio.gather( db.execute(""select 1""), db.execute(""select 2""), ) return Response.json( { ""one"": one.single_value(), ""two"": two.single_value(), } ) return [ (r""/parallel-queries$"", parallel_queries), ] Note that running parallel SQL queries in this way has been known to cause problems in the past , so treat this example with caution. Adding ?_trace=1 will show that the trace covers both of those child tasks.","[""Internals for plugins"", ""datasette.tracer""]","[{""href"": ""https://github.com/simonw/datasette/issues/2189"", ""label"": ""been known to cause problems in the past""}]" internals:internals-utils,internals,internals-utils,The datasette.utils module,"The datasette.utils module contains various utility functions used by Datasette. As a general rule you should consider anything in this module to be unstable - functions and classes here could change without warning or be removed entirely between Datasette releases, without being mentioned in the release notes. The exception to this rule is anything that is documented here. If you find a need for an undocumented utility function in your own work, consider opening an issue requesting that the function you are using be upgraded to documented and supported status.","[""Internals for plugins""]","[{""href"": ""https://github.com/simonw/datasette/issues/new"", ""label"": ""opening an issue""}]" internals:internals-utils-await-me-maybe,internals,internals-utils-await-me-maybe,await_me_maybe(value),"Utility function for calling await on a return value if it is awaitable, otherwise returning the value. This is used by Datasette to support plugin hooks that can optionally return awaitable functions. Read more about this function in The “await me maybe” pattern for Python asyncio . async datasette.utils. await_me_maybe value : Any Any If value is callable, call it. If awaitable, await it. Otherwise return it.","[""Internals for plugins"", ""The datasette.utils module""]","[{""href"": ""https://simonwillison.net/2020/Sep/2/await-me-maybe/"", ""label"": ""The “await me maybe” pattern for Python asyncio""}]" internals:internals-utils-derive-named-parameters,internals,internals-utils-derive-named-parameters,"derive_named_parameters(db, sql)","Derive the list of named parameters referenced in a SQL query, using an explain query executed against the provided database. async datasette.utils. derive_named_parameters db : Database sql : str List [ str ] Given a SQL statement, return a list of named parameters that are used in the statement e.g. for select * from foo where id=:id this would return [""id""]","[""Internals for plugins"", ""The datasette.utils module""]",[] internals:internals-utils-parse-metadata,internals,internals-utils-parse-metadata,parse_metadata(content),"This function accepts a string containing either JSON or YAML, expected to be of the format described in Metadata . It returns a nested Python dictionary representing the parsed data from that string. If the metadata cannot be parsed as either JSON or YAML the function will raise a utils.BadMetadataError exception. datasette.utils. parse_metadata content : str dict Detects if content is JSON or YAML and parses it appropriately.","[""Internals for plugins"", ""The datasette.utils module""]",[]