AlexMathew/scrapple

.. _intro-tutorials-single-linear:

===========================
Single page linear scrapers
===========================

For this example, we will extract content from a `pyvideo`_ page. Let us consider `the following page`_.

.. _pyvideo: http://pyvideo.org/
.. _the following page: http://pyvideo.org/video/1785/python-for-humans-1

To generate a skeleton configuration file, use the ``genconfig`` command. The primary arguments for the command are the project name and the URL of the base page. 

::

    $ scrapple genconfig pyvideo \
    > http://pyvideo.org/video/1785/python-for-humans-1

This will create pyvideo.json which will initially look like this -

::

    {

        "scraping": {
            "url": "http://pyvideo.org/video/1785/python-for-humans-1",
            "data": [
                {
                    "field": "",
                    "attr": "",
                    "selector": "",
                    "default": ""
                }
            ]
        },
        "project_name": "pyvideo",
        "selector_type": "xpath"

    }

You can edit this json file to specify selectors for the various data that you would want to extract from the given page.

For example, 

::

    {

        "scraping": {
            "url": "http://pyvideo.org/video/1785/python-for-humans-1",
            "data": [
                {
                    "field": "title",
                    "attr": "text",
                    "selector": "//h3",
                    "default": ""
                },
                {
                    "field": "speaker_name",
                    "attr": "text",
                    "selector": "//div[@id='sidebar']//dd[2]//a",
                    "default": ""
                },
                {
                    "field": "speaker_link",
                    "attr": "href",
                    "selector": "//div[@id='sidebar']//dd[2]//a",
                    "default": ""
                },
                {
                    "field": "event_name",
                    "attr": "text",
                    "selector": "//div[@id='sidebar']//dd[1]//a",
                    "default": ""
                },
                {
                    "field": "event_link",
                    "attr": "href",
                    "selector": "//div[@id='sidebar']//dd[1]//a",
                    "default": ""
                }
            ]
        },
        "project_name": "pyvideo",
        "selector_type": "xpath"

    }

Using this configuration file, you could generate a Python script using ``scrapple generate`` or directly run the scraper using ``scrapple run``.

The ``generate`` and ``run`` commands take two positional arguments - the project name and the output file name.

To generate the Python script -

::
    
    $ scrapple generate pyvideo talk1

This will create talk1.py, which is the script that can be run to replicate the action of ``scrapple run``.

.. code-block:: python

    from __future__ import print_function
    import json
    import os

    from scrapple.selectors.xpath import XpathSelector


    def task_pyvideo():
        """
        Script generated using 
        `Scrapple <http://scrappleapp.github.io/scrapple>`_
        """
        results = dict()
        results['project'] = "pyvideo"
        results['data'] = list()
        try:
            r0 = dict()
            page0 = XpathSelector(
            "http://pyvideo.org/video/1785/python-for-humans-1"
            )
            r0["title"] = page0.extract_content(
            "//h3", "text", ""
            )
            r0["speaker_name"] = page0.extract_content(
            "//div[@id='sidebar']//dd[2]//a", "text", ""
            )
            r0["speaker_link"] = page0.extract_content(
            "//div[@id='sidebar']//dd[2]//a", "href", ""
            )
            r0["event_name"] = page0.extract_content(
            "//div[@id='sidebar']//dd[1]//a", "text", ""
            )
            r0["event_link"] = page0.extract_content(
            "//div[@id='sidebar']//dd[1]//a", "href", ""
            )
            results['data'].append(r0)
        except KeyboardInterrupt:
            pass
        except Exception as e:
            print(e)
        finally:
            with open(os.path.join(os.getcwd(), 'talk1.json'), 'w') as f:
                json.dump(results, f)
        

    if __name__ == '__main__':
        task_pyvideo()


To run the scraper -

::

    $ scrapple run pyvideo talk1

This will create talk1.json, which contains the extracted information.

::

    {

        "project": "test1",
        "data": [
            {
                "event_name": "PyCon US 2013",
                "event_link": "/category/33/pycon-us-2013",
                "speaker_link": "/speaker/726/kenneth-reitz",
                "speaker_name": "Kenneth Reitz",
                "title": "Python for Humans"
            }
        ]

    }