Learning Scrapy by Dimitris Kouzis - Loukas

Author:Dimitris Kouzis - Loukas
Language: eng
Format: mobi, epub
Publisher: Packt Publishing
Published: 2016-01-29T23:00:00+00:00

Deferreds and deferred chains

Deferreds are the most essential mechanism that Twisted offers to help us write asynchronous code. Twisted APIs use deferreds to allow us to define sequences of actions that take place when certain events occur. Let's have a look at them.

Tip

You can get all the source code of this book from GitHub. To download this code go to git clone https://github.com/scalingexcellence/scrapybook

The full code from this chapter will be in the ch08 directory, and for this example in particular, in the ch08/deferreds.py file, and you can run it with ./deferreds.py 0.

You can use a Python console to run the following experiments interactively:

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