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Python Web Scraping

You're reading from   Python Web Scraping Hands-on data scraping and crawling using PyQT, Selnium, HTML and Python

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Product type Paperback
Published in May 2017
Publisher
ISBN-13 9781786462589
Length 220 pages
Edition 2nd Edition
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Author (1):
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Katharine Jarmul Katharine Jarmul
Author Profile Icon Katharine Jarmul
Katharine Jarmul
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Toc

Performance

To further understand how increasing the number of threads and processes affects the time required when downloading, here is a table of results for crawling 500 web pages:

Script Number of threads Number of processes Time Comparison with sequential Errors Seen?
Sequential 1 1 1349.798s 1 N
Threaded 5 1 361.504s 3.73 N
Threaded 10 1 275.492s 4.9 N
Threaded 20 1 298.168s 4.53 Y
Processes 2 2 726.899s 1.86 N
Processes 2 4 559.93s 2.41 N
Processes 2 8 451.772s 2.99 Y
Processes 5 2 383.438s 3.52 N
Processes 5 4 156.389s 8.63 Y
Processes 5 8 296.610s 4.55 Y

The fifth column shows the proportion of time in comparison to the base case of sequential downloading. We can see that the increase in performance is not linearly proportional to the number of threads and processes but appears logarithmic, that is, until adding more threads actually decreases performance. For example, one process...

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