Magic decorator syntax for asynchronous code.
Magic decorator syntax for asynchronous code in Python
Tomorrow is conveniently available via pip:
pip install tomorrow
or installable via git clone and setup.py
git clone firstname.lastname@example.org:madisonmay/Tomorrow.git sudo python setup.py install
The tomorrow library enables you to utilize the benefits of multi-threading with minimal concern about the implementation details.
Behind the scenes, the library is a thin wrapper around the Future object in concurrent.futures that resolves the Future whenever you try to access any of its attributes.
Enough of the implementation details, let’s take a look at how simple it is to speed up an inefficient chunk of blocking code with minimal effort.
Naive Web Scraper
You’ve collected a list of urls and are looking to download the HTML of the lot. The following is a perfectly reasonable first stab at solving the task.
For the following examples, we’ll be using the top sites from the Alexa rankings.
urls = [ 'http://google.com', 'http://facebook.com', 'http://youtube.com', 'http://baidu.com', 'http://yahoo.com', ]
Right then, let’s get on to the code.
import time import requests def download(url): return requests.get(url) if __name__ == "__main__": start = time.time() responses = [download(url) for url in urls] html = [response.text for response in responses] end = time.time() print "Time: %f seconds" % (end - start)
More Efficient Web Scraper
Using tomorrow’s decorator syntax, we can define a function that executes in multiple threads. Individual calls to download are non-blocking, but we can largely ignore this fact and write code identically to how we would in a synchronous paradigm.
import time import requests from tomorrow import threads @threads(5) def download(url): return requests.get(url) if __name__ == "__main__": import time start = time.time() responses = [download(url) for url in urls] html = [response.text for response in responses] end = time.time() print "Time: %f seconds" % (end - start)
Awesome! With a single line of additional code (and no explicit threading logic) we can now download websites ~10x as efficiently.
You can also optionally pass in a timeout argument, to prevent hanging on a task that is not guaranteed to return.
import time from tomorrow import threads @threads(1, timeout=0.1) def raises_timeout_error(): time.sleep(1) if __name__ == "__main__": print raises_timeout_error()
How Does it Work?
Feel free to read the source for a peek behind the scenes – it’s less that 50 lines of code.