Extract Google Scholar results using Python (or R)
Google will block you... as it will be apparent you aren't a browser. Namely, they will detect the same request signature occurring too frequently compared with a reasonable human activity.
You can do:
- How to make urllib2 requests through Tor in Python?
- Run the code on your university computers (might not help)
- Use Google scholar API might cost you money and not giving you the full features as you can see as a humaned regular user.
Edit 2020:
You might want to check scholarly
>>> search_query = scholarly.search_author('Marty Banks, Berkeley')
>>> print(next(search_query))
{'_filled': False,
'affiliation': 'Professor of Vision Science, UC Berkeley',
'citedby': 17758,
'email': '@berkeley.edu',
'id': 'Smr99uEAAAAJ',
'interests': ['vision science', 'psychology', 'human factors', 'neuroscience'],
'name': 'Martin Banks',
'url_picture': 'https://scholar.google.com/citations?view_op=medium_photo&user=Smr99uEAAAAJ'}
I suggest you not to use specific libraries for crawling specific websites, but to use general purpose HTML libraries that are well tested and has well formed documentation such as BeautifulSoup.
For accessing websites with a browser information, you could use an url opener class with a custom user agent:
from urllib import FancyURLopener
class MyOpener(FancyURLopener):
version = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.152 Safari/537.36'
openurl = MyOpener().open
And then download the required url as follows:
openurl(url).read()
For retrieving scholar results just use http://scholar.google.se/scholar?hl=en&q=${query}
url.
To extract pieces of information from a retrieved HTML file, you could use this piece of code:
from bs4 import SoupStrainer, BeautifulSoup
page = BeautifulSoup(openurl(url).read(), parse_only=SoupStrainer('div', id='gs_ab_md'))
This piece of code extracts a concrete div
element that contains number of results shown in a Google Scholar search results page.
COPython looks correct but here's a bit of an explanation by example...
Consider f:
def f(a,b,c=1):
pass
f expects values for a and b no matter what. You can leave c blank.
f(1,2) #executes fine
f(a=1,b=2) #executes fine
f(1,c=1) #TypeError: f() takes at least 2 arguments (2 given)
The fact that you are being blocked by Google is probably due to your user-agent settings in your header... I am unfamiliar with R but I can give you the general algorithm for fixing this:
- use a normal browser (firefox or whatever) to access the url while monitoring HTTP traffic (I like wireshark)
- take note of all headers sent in the appropriate http request
- try running your script and also note the headings
- spot the difference
- set your R script to make use the headers you saw when examining browser traffic
It looks like scraping with Python and R runs into the problem where Google Scholar sees your request as a robot query due to a lack of a user-agent in the request. There is a similar question in StackExchange about downloading all pdfs linked from a web page and the answer leads the user to wget in Unix and the BeautifulSoup package in Python.
Curl also seems to be a more promising direction.