X-Git-Url: https://git.openstreetmap.org./nominatim.git/blobdiff_plain/f917fa67aa19e912db472d2eeedde631be496428..fe0ade81f59ae7a77fbf4a0493171289969a8184:/docs/library/Getting-Started.md diff --git a/docs/library/Getting-Started.md b/docs/library/Getting-Started.md index a013f40c..9f81724a 100644 --- a/docs/library/Getting-Started.md +++ b/docs/library/Getting-Started.md @@ -1,85 +1,289 @@ # 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. With the Nominatim library it is possible -to access all search functionality directly from your Python code. 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 library also misses a proper installation routine, so some manipulation - of the PYTHONPATH is required. Use is only recommended for advanced Python - programmers at the moment. +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 To use the Nominatim library, you need access to a local Nominatim database. -Follow the [installation and import instructions](../admin/) to set up your -database. +Follow the [installation](../admin/Installation.md) and +[import](../admin/Import.md) instructions to set up your database. -It is not yet possible to install it in the usual way via pip or inside a -virtualenv. To get access to the library you need to set an appropriate -PYTHONPATH. With the default installation, the python library can be found -under `/usr/local/share/nominatim/lib-python`. If you have installed -Nominatim under a different prefix, adapt the `/usr/local/` part accordingly. -You can also point the PYTHONPATH to the Nominatim source code. +The Nominatim frontend library is contained in the Python package `nominatim-api`. +You can install the latest released version directly from pip: -### A simple search example + pip install nominatim-api -To query the Nominatim database you need to first set up a connection. This -is done by creating an Nominatim API object. This object exposes all the -search functions of Nominatim that are also knwon from its web API. +To install the package from the source tree directly, run: -This code snippet implements a simple search for the town if 'Brugge': + pip install packaging/nominatim-api -=== "NominatimAPIAsync" - ``` - from pathlib import Path - import asyncio +Usually you would want to run this in a virtual environment. - import nominatim.api as napi +## A simple search example + +To query the Nominatim database you need to first set up a connection. This +is done by creating an Nominatim API object. This object exposes all the +search functions of Nominatim that are also known from its web API. - async def search(query): - api = napi.NominatimAPIAsync(Path('.')) +This code snippet implements a simple search for the town of 'Brugge': - return await api.search(query) +!!! example + === "NominatimAPIAsync" + ``` python + import asyncio - results = asyncio.run(search('Brugge')) - if not results: - print('Cannot find Brugge') - else: - print(f'Found a place at {results[0].centroid.x},{results[1].centroid.y}') - ``` + import nominatim_api as napi -=== "NominatimAPI" - ``` - from pathlib import Path + async def search(query): + async with napi.NominatimAPIAsync() as api: + return await api.search(query) - import nominatim.api as napi + results = asyncio.run(search('Brugge')) + if not results: + print('Cannot find Brugge') + else: + print(f'Found a place at {results[0].centroid.x},{results[0].centroid.y}') + ``` - api = napi.NominatimAPI(Path('.')) + === "NominatimAPI" + ``` python + import nominatim_api as napi - results = api.search('Brugge') + with napi.NominatimAPI() as api: + results = api.search('Brugge') - if not results: - print('Cannot find Brugge') - else: - print(f'Found a place at {results[0].centroid.x},{results[1].centroid.y}') - ``` + if not results: + print('Cannot find Brugge') + else: + print(f'Found a place at {results[0].centroid.x},{results[0].centroid.y}') + ``` -The Nonminatim API comes in two flavours: synchronous and asynchronous. -The complete Nominatim library is written so that it can work asynchronously. +The Nominatim library is designed around +[asyncio](https://docs.python.org/3/library/asyncio.html). `NominatimAPIAsync` +provides you with an interface of coroutines. If you have many requests to make, coroutines can speed up your applications significantly. -For smaller scripts there is also a sychronous wrapper around the API. +For smaller scripts there is also a synchronous wrapper around the API. By +using `NominatimAPI`, you get exactly the same interface using classic functions. + +The examples in this chapter will always show-case both +implementations. The documentation itself will usually refer only to +'Nominatim API class' when both flavours are meant. If a functionality is +available only for the synchronous or asynchronous version, this will be +explicitly mentioned. + +## Defining which database to use + +The [Configuration](../admin/Import.md#configuration-setup-in-env) +section explains how Nominatim is configured using the +[dotenv](https://github.com/theskumar/python-dotenv) library. +The same configuration mechanism is used with the +Nominatim API library. You should therefore be sure you are familiar with +the section. + +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. Here is the simple search +example, using the configuration from a pre-defined project directory in +`/srv/nominatim-project`: + +!!! example + === "NominatimAPIAsync" + ``` python + import asyncio + + import nominatim_api as napi + + async def search(query): + async with napi.NominatimAPIAsync('/srv/nominatim-project') as api: + return await api.search(query) + + results = asyncio.run(search('Brugge')) + if not results: + print('Cannot find Brugge') + else: + print(f'Found a place at {results[0].centroid.x},{results[0].centroid.y}') + ``` + + === "NominatimAPI" + ``` python + import nominatim_api as napi + + with napi.NominatimAPI('/srv/nominatim-project') as api: + results = api.search('Brugge') + + if not results: + print('Cannot find Brugge') + else: + print(f'Found a place at {results[0].centroid.x},{results[0].centroid.y}') + ``` + + +You may also configure Nominatim by setting environment variables. +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: + +``` +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 + import asyncio + import nominatim_api as napi + + config_params = { + 'NOMINATIM_DATABASE_DSN': 'pgsql:dbname=belgium' + } + + async def search(query): + async with napi.NominatimAPIAsync(environ=config_params) as api: + return await api.search(query) + + results = asyncio.run(search('Brugge')) + ``` + + === "NominatimAPI" + ``` python + import nominatim_api as napi + + config_params = { + 'NOMINATIM_DATABASE_DSN': 'pgsql:dbname=belgium' + } + + 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. The operating system's environment +variables will be ignored. + +## Presenting results to humans + +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 +* 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 + import asyncio + + import nominatim_api as napi + + async def search(query): + async with napi.NominatimAPIAsync() as api: + return await api.search(query, address_details=True) + + results = asyncio.run(search('Brugge')) + + locale = napi.Locales(['fr', 'en']) + for i, result in enumerate(results): + address_parts = result.address_rows.localize(locale) + print(f"{i + 1}. {', '.join(address_parts)}") + ``` + + === "NominatimAPI" + ``` python + import nominatim_api as napi + + with napi.NominatimAPI() as api: + results = api.search('Brugge', address_details=True) + + locale = napi.Locales(['fr', 'en']) + for i, result in enumerate(results): + address_parts = result.address_rows.localize(locale) + print(f"{i + 1}. {', '.join(address_parts)}") + ``` + +To request information about the address of a result, add the optional +parameter 'address_details' to your search: + +``` python +>>> results = api.search('Brugge', address_details=True) +``` + +An additional field `address_rows` will set in results that are returned. +It contains a list of all places that make up the address of the place. For +simplicity, this includes name and house number of the place itself. With +the names in this list it is possible to create a human-readable description +of the result. To do that, you first need to decide in which language the +results should be presented. As with the names in the result itself, the +places in `address_rows` contain all possible name translation for each row. + +The library has a helper class `Locale` which helps extracting a name of a +place in the preferred language. It takes a single parameter with a list +of language codes in the order of preference. So + +``` python +locale = napi.Locale(['fr', 'en']) +``` + +creates a helper class that returns the name preferably in French. If that is +not possible, it tries English and eventually falls back to the default `name` +or `ref`. + +The `Locale` object can be applied to a name dictionary to return the best-matching +name out of it: + +``` python +>>> print(locale.display_name(results[0].names)) +'Brugges' +``` + +The `address_row` field has a helper function to apply the function to all +its members and save the result in the `local_name` field. It also returns +all the localized names as a convenient simple list. This list can be used +to create a human-readable output: -### Defining which database to use +``` python +>>> address_parts = results[0].address_rows.localize(locale) +>>> print(', '.join(address_parts)) +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 `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. +For more information on address rows, see +[detailed address description](Result-Handling.md#detailed-address-description).