Scraping sul serio

Web Scraping in Python

Thomas Laetsch

Data Scientist, NYU

Sito DataCamp

https://www.datacamp.com/courses/all

Qual è il div?

# response caricato con l'HTML da https://www.datacamp.com/courses/all

course_divs = response.css('div.course-block')

print( len(course_divs) )
>>> 185

Ispeziona course-block

first_div = course_divs[0]

children = first_div.xpath('./*')

print( len(children) )
>>> 3

Il primo figlio

first_div = course_divs[0]

children = first_div.xpath('./*')

first_child = children[0]

print( first_child.extract() )
>>> <a class=... />

Il secondo figlio

first_div = course_divs[0]

children = first_div.xpath('./*')

second_child = children[1]

print( second_child.extract() )
>>> <div class=... />

Il figlio dimenticato

first_div = course_divs[0]

children = first_div.xpath('./*')

third_child = children[2]

print( third_child.extract() )
>>> <span class=... />

A elenco

In un unico selettore CSS

links = response.css('div.course-block > a::attr(href)').extract()

Passo dopo passo

# passo 1: blocchi corso
course_divs = response.css('div.course-block')

# passo 2: elementi link
hrefs = course_divs.xpath('./a/@href')

# passo 3: estrai i link
links = hrefs.extract()

A scuola!

for l in links:
    print( l )

>>> /courses/free-introduction-to-r
>>> /courses/data-table-data-manipulation-r-tutorial
>>> /courses/dplyr-data-manipulation-r-tutorial
>>> /courses/ggvis-data-visualization-r-tutorial
>>> /courses/reporting-with-r-markdown
>>> /courses/intermediate-r
...

Link ottenuti

Web Scraping in Python