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deb-python-rfc3986/docs/source/user/building.rst
2017-04-22 08:05:58 -05:00

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===============
Building URIs
===============
Constructing URLs often seems simple. There are some problems with
concatenating strings to build a URL:
- Certain parts of the URL disallow certain characters
- Formatting some parts of the URL is tricky and doing it manually isn't fun
To make the experience better |rfc3986| provides the
:class:`~rfc3986.builder.URIBuilder` class to generate valid
:class:`~rfc3986.uri.URIReference` instances. The
:class:`~rfc3986.builder.URIBuilder` class will handle ensuring that each
component is normalized and safe for real world use.
Example Usage
=============
.. note::
All of the methods on a :class:`~rfc3986.builder.URIBuilder` are
chainable (except :meth:`~rfc3986.builder.URIBuilder.finalize`).
Let's build a basic URL with just a scheme and host. First we create an
instance of :class:`~rfc3986.builder.URIBuilder`. Then we call
:meth:`~rfc3986.builder.URIBuilder.add_scheme` and
:meth:`~rfc3986.builder.URIBuilder.add_host` with the scheme and host
we want to include in the URL. Then we convert our builder object into
a :class:`~rfc3986.uri.URIReference` and call
:meth:`~rfc3986.uri.URIReference.unsplit`.
.. doctest::
>>> from rfc3986 import builder
>>> print(builder.URIBuilder().add_scheme(
... 'https'
... ).add_host(
... 'github.com'
... ).finalize().unsplit())
https://github.com
Each time you invoke a method, you get a new instance of a
:class:`~rfc3986.builder.URIBuilder` class so you can build several different
URLs from one base instance.
.. doctest::
>>> from rfc3986 import builder
>>> github_builder = builder.URIBuilder().add_scheme(
... 'https'
... ).add_host(
... 'api.github.com'
... )
>>> print(github_builder.add_path(
... '/users/sigmavirus24'
... ).finalize().unsplit())
https://api.github.com/users/sigmavirus24
>>> print(github_builder.add_path(
... '/repos/sigmavirus24/rfc3986'
... ).finalize().unsplit())
https://api.github.com/repos/sigmavirus24/rfc3986
|rfc3986| makes adding authentication credentials convenient. It takes care of
making the credentials URL safe. There are some characters someone might want
to include in a URL that are not safe for the authority component of a URL.
.. doctest::
>>> from rfc3986 import builder
>>> print(builder.URIBuilder().add_scheme(
... 'https'
... ).add_host(
... 'api.github.com'
... ).add_credentials(
... username='us3r',
... password='p@ssw0rd',
... ).finalize().unsplit())
https://us3r:p%40ssw0rd@api.github.com
Further, |rfc3986| attempts to simplify the process of adding query parameters
to a URL. For example, if we were using Elasticsearch, we might do something
like:
.. doctest::
>>> from rfc3986 import builder
>>> print(builder.URIBuilder().add_scheme(
... 'https'
... ).add_host(
... 'search.example.com'
... ).add_path(
... '_search'
... ).add_query_from(
... [('q', 'repo:sigmavirus24/rfc3986'), ('sort', 'created_at:asc')]
... ).finalize().unsplit())
https://search.example.com/_search?q=repo%3Asigmavirus24%2Frfc3986&sort=created_at%3Aasc
Finally, we provide a way to add a fragment to a URL. Let's build up a URL to
view the section of the RFC that refers to fragments:
.. doctest::
>>> from rfc3986 import builder
>>> print(builder.URIBuilder().add_scheme(
... 'https'
... ).add_host(
... 'tools.ietf.org'
... ).add_path(
... '/html/rfc3986'
... ).add_fragment(
... 'section-3.5'
... ).finalize().unsplit())
https://tools.ietf.org/html/rfc3986#section-3.5