AI/참고/trafilatura-master/docs/usage-python.rst

With Python
===========

.. meta::
    :description lang=en:
        This tutorial focuses on text extraction from web pages with Python code snippets.
        Data mining with this library encompasses HTML parsing and language identification.



The Python programming language
-------------------------------

Python can be easy to pick up whether you're a first time programmer or you're experienced with other languages:

-  Official `Python Tutorial <https://docs.python.org/3/tutorial/>`_
-  `The Hitchhiker’s Guide to Python <https://docs.python-guide.org/>`_
-  `The Best Python Tutorials (freeCodeCamp) <https://www.freecodecamp.org/news/best-python-tutorial/>`_



Step-by-step
------------

Quickstart
^^^^^^^^^^

For the basics see `quickstart documentation page <quickstart.html>`_.

.. note::
    For a hands-on tutorial see also the Python Notebook `Trafilatura Overview <https://github.com/adbar/trafilatura/blob/master/docs/Trafilatura_Overview.ipynb>`_.


Extraction functions
^^^^^^^^^^^^^^^^^^^^

The functions can be imported using ``from trafilatura import ...`` and used on raw documents (strings) or parsed HTML (LXML elements).

Main text extraction, good balance between precision and recall:

- ``extract``: Wrapper function, easiest way to perform text extraction and conversion
- ``bare_extraction``: Internal function returning bare Python variables

Additional fallback functions:

- ``baseline``: Faster extraction function targeting text paragraphs and/or JSON metadata
- ``html2txt``: Extract all text in a document, maximizing recall


Output
^^^^^^

By default, the output is in plain text (TXT) format without metadata. The following additional formats are available:

- CSV
- HTML (from version 1.11 onwards)
- JSON
- Markdown (from version 1.9 onwards)
- XML and XML-TEI (following the guidelines of the Text Encoding Initiative)

To specify the output format, use one of the following strings: ``"csv", "json", "html", "markdown", "txt", "xml", "xmltei"``.

The ``bare_extraction`` function also accepts an additional ``python`` format to work with Python on the output.

To extract and include metadata in the output, use the ``with_metadata=True`` argument.

Examples
~~~~~~~~

.. code-block:: python

    # some formatting preserved in basic XML structure
    >>> extract(downloaded, output_format="xml")

    # output in JSON format with metadata extracted
    >>> extract(downloaded, output_format="json", with_metadata=True)


Note that combining TXT, CSV and JSON formats with certain structural elements (e.g. formatting or links) triggers output in Markdown format (plain text with additional elements).



Choice of HTML elements
^^^^^^^^^^^^^^^^^^^^^^^

Customize the extraction process by including or excluding specific HTML elements:


- Text elements:
   ``include_comments=True``
       Include comment sections at the bottom of articles.
   ``include_tables=True``
       Extract text from HTML ``<table>`` elements.

- Structural elements:
   ``include_formatting=True``
        Keep structural elements related to formatting (``<b>``/``<strong>``, ``<i>``/``<emph>`` etc.)
   ``include_links=True``
        Keep link targets (in ``href="..."``)
   ``include_images=True``
        Keep track of images along with their targets (``<img>`` attributes: alt, src, title)


To operate on these elements, pass the corresponding parameters to the ``extract()`` function:

.. code-block:: python

    # exclude comments from the output
    >>> result = extract(downloaded, include_comments=False)

    # skip tables and include links in the output
    >>> result = extract(downloaded, include_tables=False, include_links=True)

    # convert relative links to absolute links where possible
    >>> extract(downloaded, output_format='xml', include_links=True, url=url)


Important notes
~~~~~~~~~~~~~~~

- ``include_comments`` and ``include_tables`` are activated by default.
- Including extra elements works best with conversion to XML formats or using ``bare_extraction()``. This allows for direct display and manipulation of the elements.
- Certain elements may not be visible in the output if the chosen format does not allow it.
- Selecting Markdown automatically includes text formatting.


.. hint::
    The heuristics used by the main algorithm change according to the presence of certain elements in the HTML. If the output seems odd, try removing a constraint (e.g. formatting) to improve the result.



The precision and recall presets
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The main extraction functions offer two presets to adjust to focus of the extraction process: ``favor_precision`` and ``favor_recall``.

These parameters allow you to change the balance between accuracy and comprehensiveness of the output.

.. code-block:: python

    >>> result = extract(downloaded, url, favor_precision=True)


Precision
~~~~~~~~~

- If your results contain too much noise, prioritize precision to focus on the most central and relevant elements.
- Additionally, you can use the ``prune_xpath`` parameter to target specific HTML elements using a list of XPath expressions.


Recall
~~~~~~

- If parts of your documents are missing, try this preset to take more elements into account.
- If content is still missing, refer to the `troubleshooting guide <troubleshooting.html>`_.



Additional functions for text extraction
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The ``html2txt`` and ``baseline`` functions offer simpler approaches to extracting text from HTML content, prioritizing performance over precision.


html2txt()
~~~~~~~~~~

The ``html2txt`` function serves as a last resort for extracting text from HTML content. It emulates the behavior of similar functions in other packages and can be used to output all possible text from a given HTML source, maximizing recall. However, it may not always produce accurate or meaningful results, as it does not consider the context of the extracted sections.

.. code-block:: python

    >>> from trafilatura import html2txt
    >>> html2txt(downloaded)


baseline()
~~~~~~~~~~

For a better balance between precision and recall, as well as improved performance, consider using the ``baseline`` function instead. This function returns a tuple containing an LXML element with the body, the extracted text as a string, and the length of the text.  It uses a set of heuristics to extract text from the HTML content, which generally produces more accurate results than ``html2txt``.

.. code-block:: python

    >>> from trafilatura import baseline
    >>> postbody, text, len_text = baseline(downloaded)

For more advanced use cases, consider using other functions in the package that provide more control and customization over the text extraction process.


Guessing if text can be found
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The function ``is_probably_readerable()`` has been ported from Mozilla's Readability.js, it is available from version 1.10 onwards and provides a way to guess if a page probably has a main text to extract.

.. code-block:: python

    >>> from trafilatura.readability_lxml import is_probably_readerable
    >>> is_probably_readerable(html)  # HTML string or already parsed tree


Language identification
^^^^^^^^^^^^^^^^^^^^^^^

The target language can also be set using 2-letter codes (ISO 639-1), there will be no output if the detected language of the result does not match and no such filtering if the identification component has not been installed (see above `installation instructions <installation.html>`_) or if the target language is not available.

.. code-block:: python

    >>> result = extract(downloaded, url, target_language="de")

.. note::
    Additional components are required: ``pip install trafilatura[all]``.
    This feature currently uses the `py3langid package <https://github.com/adbar/py3langid>`_ and is dependent on language availability and performance of the original model.


Optimizing for speed
^^^^^^^^^^^^^^^^^^^^

Execution speed not only depends on the platform and on supplementary packages (``trafilatura[all]``, ``htmldate[speed]``), but also on the extraction strategy.

The available fallbacks make extraction more precise but also slower. The use of fallback algorithms can also be bypassed in *fast* mode, which should make extraction about twice as fast:

.. code-block:: python

    # skip algorithms used as fallback
    >>> result = extract(downloaded, no_fallback=True)

The following combination usually leads to shorter processing times:

.. code-block:: python

    >>> result = extract(downloaded, include_comments=False, include_tables=False, no_fallback=True)


Extraction settings
-------------------

.. hint::
    See also `settings page <settings.html>`_.


Function parameters
^^^^^^^^^^^^^^^^^^^

Starting from version 1.9, the ``Extractor`` class provides a convenient way to define and manage extraction parameters. It allows users to customize all options used by the extraction functions and offers a convenient shortcut compared to multiple function parameters.

Here is how to use the class:

.. code-block:: python

    # import the Extractor class from the settings module
    >>> from trafilatura.settings import Extractor

    # set multiple options at once
    >>> options = Extractor(output_format="json", with_metadata=True)

    # add or adjust settings as needed
    >>> options.formatting = True  # same as include_formatting
    >>> options.source = "My Source"  # useful for debugging

    # use the options in an extraction function
    >>> extract(my_doc, options=options)


See the ``settings.py`` file for a full example.


Metadata extraction
^^^^^^^^^^^^^^^^^^^

- ``with_metadata=True``: extract metadata fields and include them in the output
- ``only_with_metadata=True``: only output documents featuring all essential metadata (date, title, url)


Date
~~~~

Among metadata extraction, dates are handled by an external module: `htmldate <https://github.com/adbar/htmldate>`_. By default, focus is on original dates and the extraction replicates the *fast/no_fallback* option.

`Custom parameters <https://htmldate.readthedocs.io/en/latest/corefunctions.html#handling-date-extraction>`_ can be passed through the extraction function or through the ``extract_metadata`` function in ``trafilatura.metadata``, most notably:

-  ``extensive_search`` (boolean), to activate further heuristics (higher recall, lower precision)
-  ``original_date`` (boolean) to look for the original publication date,
-  ``outputformat`` (string), to provide a custom datetime format,
-  ``max_date`` (string), to set the latest acceptable date manually (YYYY-MM-DD format).

.. code-block:: python

    # import the extract() function, use a previously downloaded document
    # pass the new parameters as dict
    >>> extract(downloaded, output_format="xml", date_extraction_params={
            "extensive_search": True, "max_date": "2018-07-01"
        })


URL
~~~

Even if the page to process has already been downloaded it can still be useful to pass the URL as an argument. See this `previous bug <https://github.com/adbar/trafilatura/issues/75>`_ for an example:

.. code-block:: python

    # define a URL and download the example
    >>> url = "https://web.archive.org/web/20210613232513/https://www.thecanary.co/feature/2021/05/19/another-by-election-headache-is-incoming-for-keir-starmer/"
    >>> downloaded = fetch_url(url)

    # content discarded since necessary metadata couldn't be extracted
    >>> bare_extraction(downloaded, only_with_metadata=True)
    >>>

    # date found in URL, extraction successful
    >>> bare_extraction(downloaded, only_with_metadata=True, url=url)


Memory use
^^^^^^^^^^

Trafilatura uses caches to speed up extraction and cleaning processes. This may lead to memory leaks in some cases, particularly in large-scale applications. If that happens you can reset all cached information in order to release RAM:

.. code-block:: python

    # import the function
    >>> from trafilatura.meta import reset_caches

    # use it at any given point
    >>> reset_caches()


Input/Output types
------------------

Python objects as output
^^^^^^^^^^^^^^^^^^^^^^^^

The extraction can be customized using a series of parameters, for more see the `core functions <corefunctions.html>`_ page.

The function ``bare_extraction`` can be used to bypass output conversion, it returns Python variables for  metadata (dictionary) as well as main text and comments (both LXML objects).

.. code-block:: python

    >>> from trafilatura import bare_extraction
    >>> bare_extraction(downloaded)


Raw HTTP response objects
^^^^^^^^^^^^^^^^^^^^^^^^^

The ``fetch_response()`` function can pass a response object straight to the extraction.

This can be useful to get the final redirection URL with ``response.url`` and then pass is directly as a URL argument to the extraction function:

.. code-block:: python

    # necessary components
    >>> from trafilatura import fetch_response, bare_extraction

    # load an example
    >>> response = fetch_response("https://www.example.org")

    # perform extract() or bare_extraction() on Trafilatura's response object
    >>> bare_extraction(response.data, url=response.url)  # here is the redirection URL


LXML objects
^^^^^^^^^^^^

The input can consist of a previously parsed tree (i.e. a *lxml.html* object), which is then handled seamlessly:

.. code-block:: python

    # define document and load it with LXML
    >>> from lxml import html
    >>> my_doc = """<html><body><article><p>
                    Here is the main text.
                    </p></article></body></html>"""
    >>> mytree = html.fromstring(my_doc)

    # extract from the already loaded LXML tree
    >>> extract(mytree)
    'Here is the main text.'


Interaction with BeautifulSoup
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Here is how to convert a BS4 object to LXML format in order to use it with Trafilatura:

.. code-block:: python

    >>> from bs4 import BeautifulSoup
    >>> from lxml.html.soupparser import convert_tree
    >>> from trafilatura import extract

    >>> soup = BeautifulSoup("<html><body><time>The date is Feb 2, 2024</time></body></html>", "lxml")
    >>> lxml_tree = convert_tree(soup)[0]
    >>> extract(lxml_tree)


Navigation
----------

Three potential navigation strategies are currently available: feeds (mostly for fresh content), sitemaps (for exhaustivity, all potential pages as listed by the owners) and discovery by web crawling (i.e. by following the internal links, more experimental).


Feeds
^^^^^

The function ``find_feed_urls`` is a all-in-one utility that attempts to discover the feeds from a webpage if required and/or downloads and parses feeds. It returns the extracted links as list, more precisely as a sorted list of unique links.

.. code-block:: python

    # import the feeds module
    >>> from trafilatura import feeds

    # use the homepage to automatically retrieve feeds
    >>> mylist = feeds.find_feed_urls('https://www.theguardian.com/')
    >>> mylist
    ['https://www.theguardian.com/international/rss', '...'] # and so on

    # use a predetermined feed URL directly
    >>> mylist = feeds.find_feed_urls('https://rss.nytimes.com/services/xml/rss/nyt/HomePage.xml')
    >>> mylist is not []
    True # it's not empty


.. note::
    The links are seamlessly filtered for patterns given by the user, e.g. using ``https://www.un.org/en/`` as argument implies taking all URLs corresponding to this category.


An optional argument ``target_lang`` makes it possible to filter links according to their expected target language. A series of heuristics are applied on the link path and parameters to try to discard unwanted URLs, thus saving processing time and download bandwidth.


.. code-block:: python

    # the feeds module has to be imported
    # search for feeds in English
    >>> mylist = feeds.find_feed_urls('https://www.un.org/en/rss.xml', target_lang='en')
    >>> mylist is not []
    True # links found as expected

    # target_lang set to Japanese, the English links are discarded
    >>> mylist = feeds.find_feed_urls('https://www.un.org/en/rss.xml', target_lang='ja')
    >>> mylist
    []

For more information about feeds and web crawling see:

- This blog post: `Using RSS and Atom feeds to collect web pages with Python <https://adrien.barbaresi.eu/blog/using-feeds-text-extraction-python.html>`_
- This Youtube tutorial: `Extracting links from ATOM and RSS feeds <https://www.youtube.com/watch?v=NW2ISdOx08M&list=PL-pKWbySIRGMgxXQOtGIz1-nbfYLvqrci&index=2&t=136s>`_


Sitemaps
^^^^^^^^

- Youtube tutorial: `Learn how to process XML sitemaps to extract all texts present on a website <https://www.youtube.com/watch?v=uWUyhxciTOs>`_

.. code-block:: python

    # load sitemaps module
    >>> from trafilatura import sitemaps

    # automatically find sitemaps by providing the homepage
    >>> mylinks = sitemaps.sitemap_search('https://www.theguardian.com/')

    # the target_lang argument works as explained above
    >>> mylinks = sitemaps.sitemap_search('https://www.un.org/', target_lang='en')

The links are also seamlessly filtered for patterns given by the user, e.g. using ``https://www.theguardian.com/society`` as argument implies taking all URLs corresponding to the society category.


Web crawling
^^^^^^^^^^^^

See the `documentation page on web crawling <crawls.html>`_ for more information.


.. hint::
    For more information on how to refine and filter a URL collection, see the underlying `courlan <https://github.com/adbar/courlan>`_ library.


Deprecations
------------

The following functions and arguments are deprecated:

- extraction:
   - ``process_record()`` function → use ``extract()`` instead
   - ``csv_output``, ``json_output``, ``tei_output``, ``xml_output`` → use ``output_format`` parameter instead
   - ``bare_extraction(as_dict=True)`` → the function returns a ``Document`` object, use ``.as_dict()`` method on it
   - ``bare_extraction()`` and ``extract()``: ``no_fallback`` → use ``fast`` instead
   - ``max_tree_size`` parameter moved to ``settings.cfg`` file
- downloads: ``decode`` argument in ``fetch_url()`` → use ``fetch_response`` instead
- utils: ``decode_response()`` function → use ``decode_file()`` instead
- metadata: ``with_metadata`` (include metadata) had once the effect of today's ``only_with_metadata`` (only documents with necessary metadata)