Web Scraping with Python

Paul Schreiber
paul.schreiber@ﬁvethirtyeight.com
paulschreiber@gmail.com
@paulschreiber

Fetching pages
➜ urllib

➜ urllib2

➜ urllib (Python 3)

➜ requests

import'requests'
page'='requests.get('http://www.ire.org/')
Fetch one page

import'requests'
base_url'=''http://www.fishing.ocean/p/%s''
for'i'in'range(0,'10):'
''url'='base_url'%'i'
''page'='requests.get(url)
Fetch a set of results

import'requests'
page'='requests.get('http://www.ire.org/')'
with'open("index.html",'"wb")'as'html:'
''html.write(page.content)
Download a ﬁle

Parsing data
➜ Regular Expressions

➜ CSS Selectors

➜ XPath

➜ Object Hierarchy

➜ Object Searching

<html>'
''<head><title>Green'Eggs'and'Ham</title></head>'
''<body>'
'''<ol>'
''''''<li>Green'Eggs</li>'
''''''<li>Ham</li>'
'''</ol>'
''</body>'
</html>

import're'
item_re'='re.compile("<li[^>]*>([^<]+?)</
li>")'
item_re.findall(html)
Regular Expressions DON’T
DO THIS!

from'bs4'import'BeautifulSoup'
soup'='BeautifulSoup(html)'
[s.text'for's'in'soup.select("li")]
CSS Selectors

from'lxml'import'etree'
from'StringIO'import'*'
html'='StringIO(html)'
tree'='etree.parse(html)'
[s.text'for's'in'tree.xpath('/ol/li')]
XPath

import'requests'
page'='requests.get('http://www.ire.org/')'
soup'='BeautifulSoup(page.content)'
print'"The'title'is'"'+'soup.title
Object Hierarchy

soup'='BeautifulSoup(html)'
[s.text'for's'in'soup.find_all("li")]
Object Searching

import'csv'
with'open('shoes.csv',''wb')'as'csvfile:'
''''shoe_writer'='csv.writer(csvfile)'
''''for'line'in'shoe_list:'
''''''''shoe_writer.writerow(line)'
Write CSV

output'='open("shoes.txt",'"w")'
for'row'in'data:'
''''output.write("t".join(row)'+'"n")'
output.close()'
Write TSV

import'json'
with'open('shoes.json',''wb')'as'outfile:'
''''json.dump(my_json,'outfile)'
Write JSON

WTA Rankings
➜ fetch page

➜ parse cells

➜ write to ﬁle

import'csv'
import'requests'
url'=''http://www.wtatennis.com/singlesZ
rankings''
page'='requests.get(url)'
soup'='BeautifulSoup(page.content)
WTA Rankings

soup.select("#myTable'td")
WTA Rankings

[s'for's'in'soup.select("#myTable'td")]
WTA Rankings

[s.get_text()'for's'in'
soup.select("#myTable'td")]
WTA Rankings

[s.get_text().strip()'for's'in'
WTA Rankings

cells'='[s.get_text().strip()'for's'in'
WTA Rankings

''print'cells[i*7:i*7+7]
WTA Rankings

with'open('wta.csv',''wb')'as'csvfile:'
''wtawriter'='csv.writer(csvfile)'
''for'i'in'range(0,'3):'
''''wtawriter.writerow(cells[i*7:i*7+7])
WTA Rankings

NY Election Boards
➜ list counties

➜ loop over counties

➜ fetch county pages

➜ parse county data

➜ write to ﬁle

import'requests'
url'=''http://www.elections.ny.gov/
CountyBoards.html''
soup'='BeautifulSoup(page.content)
NY Election Boards

soup.select("area")
NY Election Boards

counties'='soup.select("area")'
county_urls'='[u.get('href')'for'u'in'
counties]
NY Election Boards

counties'='soup.select("area")'
county_urls'='[u.get('href')'for'u'in'
counties]'
county_urls'='county_urls[1:]'
county_urls'='list(set(county_urls))
NY Election Boards

for'url'in'county_urls[0:3]:'
''''print'"Fetching'%s"'%'url'
''''page'='requests.get(url)'
''''soup'='BeautifulSoup(page.content)'
''''lines'='[s'for's'in'soup.select("th")
[0].strings]'
''''data.append(lines)
NY Election Boards

output'='open("boards.txt",'"w")'
for'row'in'data:'
''''output.write("t".join(row)'+'"n")'
output.close()
NY Election Boards

ACEC Members
➜ loop over pages

➜ fetch result table

➜ parse name, id, location

➜ write to ﬁle

import'requests'
import'json'
base_url'=''http://www.acec.ca/about_acec/
search_member_firms/
business_sector_search.html/search/
business/page/%s'
ACEC Members

url'='base_url'%'1'
soup.find(id='resulttable')
ACEC Members

url'='base_url'%'1'
table'='soup.find(id='resulttable')'
rows'='table.find_all('tr')
ACEC Members

url'='base_url'%'1'
table'='soup.find(id='resulttable')'
rows'='table.find_all('tr')'
columns'='rows[0].find_all('td')
ACEC Members

columns'='rows[0].find_all('td')'
company_data'='{'
'''name':'columns[1].a.text,'
'''id':'columns[1].a['href'].split('/')
[Z1],'
'''location':'columns[2].text'
}
ACEC Members

start_page'='1'
end_page'='2'
result'='[]
ACEC Members

for'i'in'range(start_page,'end_page'+'1):'
''''url'='base_url'%'i'
''''print'"Fetching'%s"'%'url'
''''page'='requests.get(url)'
''''soup'='BeautifulSoup(page.content)'
''''table'='soup.find(id='resulttable')'
''''rows'='table.find_all('tr')
ACEC Members

''for'r'in'rows:'
''''columns'='r.find_all('td')'
''''company_data'='{'
'''''''name':'columns[1].a.text,'
'''''''id':'columns[1].a['href'].split('/')[Z1],'
'''''''location':'columns[2].text'
''''}'
''''result.append(company_data)'
ACEC Members

with'open('acec.json',''w')'as'outfile:'
''''json.dump(result,'outfile)
ACEC Members

Python Tools
➜ lxml

➜ scrapy

➜ MechanicalSoup

➜ RoboBrowser

➜ pyQuery

Ruby Tools
➜ nokogiri

➜ Mechanize

Not coding? Scrape with:
➜ import.io

➜ Kimono

➜ copy & paste

➜ PDFTables

➜ Tabula

page'='requests.get(url,'auth=('drseuss','
'hamsandwich'))
Basic Authentication

page'='requests.get(url,'verify=False)
Self-signed certiﬁcates

page'='requests.get(url,'verify='/etc/ssl/
certs.pem')
Specify Certiﬁcate Bundle

requests.exceptions.SSLError:5hostname5
'shrub.ca'5doesn't5match5either5of5
'www.arthurlaw.ca',5'arthurlaw.ca'5
$'pip'install'pyopenssl'
$'pip'install'ndgZhttpsclient'
$'pip'install'pyasn1
Server Name Indication (SNI)

UnicodeEncodeError:''ascii','u'Cornet,'
Alizxe9','12,'13,''ordinal'not'in'
range(128)''
Fix
myvar.encode("utfZ8")
Unicode

if'(page.status_code'>='400):'
''...'
else:'
''...
Server Errors

try:'
''''r'='requests.get(url)'
except'requests.exceptions.RequestException'as'e:'
''''print'e'
''''sys.exit(1)'
Exceptions

headers'='{'
'''''UserZAgent':''Mozilla/3000''
}'
response'='requests.get(url,'headers=headers)
Browser Disallowed

import'time'
''url'='base_url'%'i'
''page'='requests.get(url)'
''time.sleep(1)
Rate Limiting/Slow Servers

requests.get("http://greeneggs.ham/",'params='
{'name':''sam',''verb':''are'})
Query String

requests.post("http://greeneggs.ham/",'data='
{'name':''sam',''verb':''are'})
POST a form

github.com/paulschreiber/nicar15

Many graphics from The Noun Project

Binoculars by Stephen West. Broken ﬁle by Maxi Koichi.

Broom by Anna Weiss. Chess by Matt Brooks.

Cube by Luis Rodrigues. Firewall by Yazmin Alanis.

Frown by Simple Icons. Lock by Edward Boatman.

Wrench by Tony Gines.

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