Before working with Grab ensure that you have the latest version. The recommended way of installing Grab is by using pip:
pip install -U Grab
You should also manually install the lxml and pycurl libraries.
Let's get started with some simple examples.
First, you need to import the Grab class:
>>> from grab import Grab
Then you can build Grab instances and make simple network requests:
>>> from grab import Grab >>> g = Grab() >>> resp = g.go('http://livejournal.com/')
Now, we have a Response object which provides an interface to the response's content, cookies, headers and other things.
We've just made a GET request. To make other request types, you need to configure the Grab instance via the setup method with the method argument:
>>> g.setup(method='put') >>> g.setup(method='delete') >>> g.setup(method='options') >>> g.setup(method='head')
Let's see a small example of HEAD request:
>>> g = Grab() >>> g.setup(method='head') >>> resp = g.go('http://google.com/robots.txt') >>> print len(resp.body) 0 >>> print resp.headers['Content-Length'] 1776
When you build site scrapers or work with network APIs it is a common task to create POST requests. You can build POST request using the post option:
>>> g = Grab() >>> g.setup(post={'username': 'Root', 'password': 'asd7DD&*ssd'}) >>> g.go('http://example.com/log-in-form')
Another common task is to get a web form, fill it in and submit it. Grab provides an easy way to work with forms:
>>> g = Grab() >>> g.go('http://example/com/log-in') >>> g.set_input('username', 'Foo') >>> g.set_input('password', 'Bar') >>> g.submit()
When you call submit, Grab will build a POST request using the values passed in via set_input. If you did not specify values for some form elements then Grab will use their default values.
Grab also provides an interface to upload files:
>>> from grab import Grab, UploadFile >>> g = Grab() >>> g.setup(post={'name': 'Flower', 'file': UploadFile('/path/to/image.png')}) >>> g.submit()
Also you can upload files via the form API:
>>> from grab import Grab, UloadFile >>> g = Grab() >>> g.go('http://example.com/some-form') >>> g.set_input('name', 'A flower') >>> g.set_input('file', UploadFile('/path/to/image.png')) >>> g.submit()
Consider a simple page retrieving example:
>>> g = Grab() >>> resp = g.go('http://google.com/')
To get the response content as unicode use:
>>> resp.unicode_body()
Note that grab will automatically detect the character set (charset for short) of the response content and convert it to unicode. You can detected the charset with:
>>> resp.charset
If you need the original response body then use:
>>> resp.body
Original content is useful if you need to save a binary file (e.g. an image):
>>> resp = g.go('http://example.com/some-log.png') >>> open('logo.png', 'w').write(resp.body)
The gzip and deflate encodings are automatically decoded.
TO BE CONTINUED