PyJSONProxy - simple proxy and scraper

simple proxy

AJAX requests are restricted by the same origin policy. This can be bypassed by using either JSONP, CORS_ or a local proxy. This implements the third variant. So you can do something like this::

$ curl http://localhost:5000/github/xi/
{
  "login": "xi",
  ...
}

With a configuration like this::

ENDPOINTS = {
    'github': {
        'host': 'https://api.github.com/users/'
    }
}

scraping

Maybe the more interesting part is that this also contains a simple scraping mechanism. So if a service does not offer an API but only plain HTML pages, PyJSONProxy can extract information from there::

$ curl http://localhost:5000/github/xi/
{
  "url": "https://github.com/xi/",
  "login": "xi",
  "activity": [
    ...
  ],
  "repos": [{
    ...
  }]
  ...
}

::

ENDPOINTS = {
    'github': {
        'host': 'https://github.com/',
        'fields': {
            'login': '.vcard-username',
            'fullname': '.vcard-fullname',
            'email': '.vcard-details .email',
            'join-date': '.vcard-details .join-date@datetime',
            'activity': {
                'selector': '.contribution-activity-listing ul a'
            },
            'repos': {
                'selector': '.popular-repos a.mini-repo-list-item',
                'fields': {
                    'url': '@href',
                    'name': '.repo',
                    'description': '.repo-description'
                }
            }
        }
    }
}

Selectors are generally CSS-selectors with the additional option to select an attribute by appending an @ and the attribute name. If no attribute is selected, the text content of the element will be used.

CORS header

By setting ALLOW_CORS to True, an Access-Control-Allow-Origin-header with value * will be set for all responses.

Documentation

Some simple documentation is automatically generated and available under / (for all endpoints) or /{endpoint}/ (for an individual endpoint). To provide some input for this documentation, you can add a description to both endpoints and fields::

ENDPOINTS = {
    'github': {
        'host': 'https://github.com/',
        'doc': 'Access data about GitHub users',
        'fields': {
          'login': '.vcard-username',
          'fullname': '.vcard-fullname',
          'email': '.vcard-details .email'
          'join-date': '.vcard-details .join-date@datetime'
        },
        'fields_doc': {
          'login': 'github username',
          'fullname': 'the user\'s full name',
          'join-date': 'date when the user joined github in ISO-xx format'
        }
    }
}

Note on security and performance

Security and performance were not a priority in this project. So it might be bad.

.. _same origin policy: https://developer.mozilla.org/en-US/docs/Web/Security/Same-origin_policy .. _JSONP: https://en.wikipedia.org/wiki/JSONP .. _CORS: https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS