From: Sarah Hoffmann Date: Thu, 29 Aug 2024 20:45:20 +0000 (+0200) Subject: docs: rework library getting started X-Git-Url: https://git.openstreetmap.org./nominatim.git/commitdiff_plain/f52212abbd21d5139e893b53d75fff5a17893010 docs: rework library getting started --- diff --git a/docs/library/Getting-Started.md b/docs/library/Getting-Started.md index 1f5b2baa..6206022f 100644 --- a/docs/library/Getting-Started.md +++ b/docs/library/Getting-Started.md @@ -1,16 +1,21 @@ # Getting Started -The Nominatim search frontend can directly be used as a Python library in -scripts and applications. When you have imported your own Nominatim database, -then it is no longer necessary to run a full web service for it and access -the database through http requests. There are -also less constraints on the kinds of data that can be accessed. The library -allows to get access to more detailed information about the objects saved -in the database. - -!!! danger - The library interface is currently in an experimental stage. There might - be some smaller adjustments to the public interface until the next version. +The Nominatim search frontend is implemented as a Python library and can as +such directly be used in Python scripts and applications. You don't need to +set up a web frontend and access it through HTTP calls. The library gives +direct access to the Nominatim database through similar search functions as +offered by the web API. In addition, it will give you a more complete and +detailed view on the search objects stored in the database. + +!!! warning + + The Nominatim library is used for accessing a local Nominatim database. + It is not meant to be used against web services of Nominatim like the + one on https://nominatim.openstreetmap.org. If you need a Python library + to access these web services, have a look at + [GeoPy](https://geopy.readthedocs.io). Don't forget to consult the + usage policy of the service you want to use before accessing such + a web service. ## Installation @@ -19,6 +24,10 @@ Follow the [installation](../admin/Installation.md) and [import](../admin/Import.md) instructions to set up your database. The Nominatim frontend library is contained in the Python package `nominatim-api`. +You can install the latest released version directly from pip: + + pip install nominatim-api + To install the package from the source tree directly, run: pip install packaging/nominatim-api @@ -36,15 +45,13 @@ This code snippet implements a simple search for the town of 'Brugge': !!! example === "NominatimAPIAsync" ``` python - from pathlib import Path import asyncio import nominatim_api as napi async def search(query): - api = napi.NominatimAPIAsync(Path('.')) - - return await api.search(query) + async with napi.NominatimAPIAsync() as api: + return await api.search(query) results = asyncio.run(search('Brugge')) if not results: @@ -55,13 +62,10 @@ This code snippet implements a simple search for the town of 'Brugge': === "NominatimAPI" ``` python - from pathlib import Path - import nominatim_api as napi - api = napi.NominatimAPI(Path('.')) - - results = api.search('Brugge') + with napi.NominatimAPI() as api: + results = api.search('Brugge') if not results: print('Cannot find Brugge') @@ -93,25 +97,31 @@ The same configuration mechanism is used with the Nominatim API library. You should therefore be sure you are familiar with the section. -The constructor of the 'Nominatim API class' takes one mandatory parameter: -the path to the [project directory](../admin/Import.md#creating-the-project-directory). -You should have set up this directory as part of the Nominatim import. -Any configuration found in the `.env` file in this directory will automatically -used. +There are three different ways, how configuration options can be set for +a 'Nominatim API class'. When you have set up your Nominatim database, you +have normally created a [project directory](../admin/Import.md#creating-the-project-directory) +which stores the various configuration and customization files that Nominatim +needs. You may pass the location of the project directory to your +'Nominatim API class' constructor and it will read the .env file in the +directory and set the configuration accordingly. You may also configure Nominatim by setting environment variables. -Normally, Nominatim will check the operating system environment. This can be -overwritten by giving the constructor a dictionary of configuration parameters. +Normally Nominatim will check the operating system environment. Lets +say you want to look up 'Brugge' in the special database named 'belgium' instead of the +standard 'nominatim' database. You can run the example script above like this: -Let us look up 'Brugge' in the special database named 'belgium' instead of the -standard 'nominatim' database: +``` +NOMINATIM_DATABASE_DSN=pgsql:dbname=belgium python3 example.py +``` + +The third option to configure the library is to hand in the configuration +parameters into the 'Nominatim API class'. Changing the database would look +like this: !!! example === "NominatimAPIAsync" ``` python - from pathlib import Path import asyncio - import nominatim_api as napi config_params = { @@ -119,50 +129,53 @@ standard 'nominatim' database: } async def search(query): - api = napi.NominatimAPIAsync(Path('.'), environ=config_params) - - return await api.search(query) + async with napi.NominatimAPIAsync(environ=config_params) as api: + return await api.search(query) results = asyncio.run(search('Brugge')) ``` === "NominatimAPI" ``` python - from pathlib import Path - import nominatim_api as napi config_params = { 'NOMINATIM_DATABASE_DSN': 'pgsql:dbname=belgium' } - api = napi.NominatimAPI(Path('.'), environ=config_params) - - results = api.search('Brugge') + with napi.NominatimAPI(environ=config_params) as api: + results = api.search('Brugge') ``` +When the `environ` parameter is given, then only configuration variables +from this dictionary will be used. + ### Presenting results to humans -All search functions return the raw results from the database. There is no -full human-readable label. To create such a label, you need two things: +All search functions return full result objects from the database. Such a +result object contains lots of details: names, address information, OSM tags etc. +This gives you lots of flexibility what to do with the results. + +One of the most common things to get is some kind of human-readable label +that describes the result in a compact form. Usually this would be the name +of the object and some parts of the address to explain where in the world +it is. To create such a label, you need two things: * the address details of the place -* adapt the result to the language you wish to use for display +* all names for the label adapted to the language you wish to use for display Again searching for 'Brugge', this time with a nicely formatted result: !!! example === "NominatimAPIAsync" ``` python - from pathlib import Path import asyncio import nominatim_api as napi async def search(query): - api = napi.NominatimAPIAsync(Path('.')) - - return await api.search(query, address_details=True) + async with napi.NominatimAPIAsync() as api: + return await api.search(query, address_details=True) results = asyncio.run(search('Brugge')) @@ -174,13 +187,10 @@ Again searching for 'Brugge', this time with a nicely formatted result: === "NominatimAPI" ``` python - from pathlib import Path - import nominatim_api as napi - api = napi.NominatimAPI(Path('.')) - - results = api.search('Brugge', address_details=True) + with napi.NominatimAPI() as api: + results = api.search('Brugge', address_details=True) locale = napi.Locales(['fr', 'en']) for i, result in enumerate(results): @@ -236,7 +246,7 @@ Bruges, Flandre-Occidentale, Flandre, Belgique This is a fairly simple way to create a human-readable description. The place information in `address_rows` contains further information about each -place. For example, which OSM `adlin_level` was used, what category the place +place. For example, which OSM `admin_level` was used, what category the place belongs to or what rank Nominatim has assigned. Use this to adapt the output to local address formats.