How to extract URL from a redirect URL using regex in Python?

Question

I have the following test_string from which I need to obtain the actual URL.

Test string (partly shown):

An experimental and modeling study of autoignition characteristics of
butanol/diesel blends over wide temperature ranges
<http://scholar.google.com/scholar_url?url=3Dhttps://www.sciencedirect.com/=
science/article/pii/S0010218020301346&hl=3Den&sa=3DX&d=3D448628313728630325=
1&scisig=3DAAGBfm26Wh2koXdeGZkQxzZbenQYFPytLQ&nossl=3D1&oi=3Dscholaralrt&hi=
st=3Dv2Y_3P0AAAAJ:17949955323429043383:AAGBfm1nUe-t2q_4mKFiHSHFEAo0A4rRSA>
Y Qiu, W Zhou, Y Feng, S Wang, L Yu, Z Wu, Y Mao=E2=80=A6 - Combustion and =
Flame,
2020

Desired output for part of test_string

https://www.sciencedirect.com/science/article/pii/S0010218020301346

I have been trying to obtain this with the MWE given below applied to many strings, but it gives only one URL.

MWE

from urlparse import urlparse, parse_qs
import re
from re import search

test_string = '''
Production, Properties, and Applications of ALPHA-Terpineol
<http://scholar.google.com/scholar_url?url=https://link.springer.com/content/pdf/10.1007/s11947-020-02461-6.pdf&hl=en&sa=X&d=12771069332921982368&scisig=AAGBfm1tFjLUm7GV1DRnuYCzvR4uGWq9Cg&nossl=1&oi=scholaralrt&hist=v2Y_3P0AAAAJ:17949955323429043383:AAGBfm1nUe-t2q_4mKFiHSHFEAo0A4rRSA>

A Sales, L de Oliveira Felipe, JL Bicas
Abstract ALPHA-Terpineol (CAS No. 98-55-5) is a tertiary monoterpenoid 
alcohol widely
and commonly used in the flavors and fragrances industry for its sensory 
properties.
It is present in different natural sources, but its production is mostly 
based on ...
Save 
<http://scholar.google.com/citations?update_op=email_library_add&info=oB2z7uTzO7EJ&citsig=AMD79ooAAAAAYLfmix3sQyUWnFrHeKYZxuK31qlqlbCh&hl=en> 
    Twitter 
<http://scholar.google.com/scholar_share?hl=en&oi=scholaralrt&ss=tw&url=https://link.springer.com/content/pdf/10.1007/s11947-020-02461-6.pdf&rt=Production,+Properties,+and+Applications+of+%CE%B1-Terpineol&scisig=AAGBfm0yXFStqItd97MUyPT5nRKLjPIK6g> 
    Facebook 
<http://scholar.google.com/scholar_share?hl=en&oi=scholaralrt&ss=fb&url=https://link.springer.com/content/pdf/10.1007/s11947-020-02461-6.pdf&rt=Production,+Properties,+and+Applications+of+%CE%B1-Terpineol&scisig=AAGBfm0yXFStqItd97MUyPT5nRKLjPIK6g> 

An experimental and modeling study of autoignition characteristics of
butanol/diesel blends over wide temperature ranges
<http://scholar.google.com/scholar_url?url=3Dhttps://www.sciencedirect.com/=
science/article/pii/S0010218020301346&hl=3Den&sa=3DX&d=3D448628313728630325=
1&scisig=3DAAGBfm26Wh2koXdeGZkQxzZbenQYFPytLQ&nossl=3D1&oi=3Dscholaralrt&hi=
st=3Dv2Y_3P0AAAAJ:17949955323429043383:AAGBfm1nUe-t2q_4mKFiHSHFEAo0A4rRSA>
Y Qiu, W Zhou, Y Feng, S Wang, L Yu, Z Wu, Y Mao=E2=80=A6 - Combustion and =
Flame,
2020
Butanol/diesel blend is considered as a very promising alternative fuel
with
agreeable combustion and emission performance in engines. This paper
intends to
further investigate its autoignition characteristics with the combination
of a heated =E2=80=A6
[image: Save]
<http://scholar.google.com/citations?update_op=3Demail_library_add&info=3DE=
27Gd756Qj4J&citsig=3DAMD79ooAAAAAYImDxwWCwd5S5xIogWp9RTavFRMtTDgS&hl=3Den>
[image:
Twitter]
<http://scholar.google.com/scholar_share?hl=3Den&oi=3Dscholaralrt&ss=3Dtw&u=
rl=3Dhttps://www.sciencedirect.com/science/article/pii/S0010218020301346&rt=
=3DAn+experimental+and+modeling+study+of+autoignition+characteristics+of+bu=
tanol/diesel+blends+over+wide+temperature+ranges&scisig=3DAAGBfm19DOLNm3-Fl=
WaO0trAxZkeidxYWg>
[image:
Facebook]
<http://scholar.google.com/scholar_share?hl=3Den&oi=3Dscholaralrt&ss=3Dfb&u=
rl=3Dhttps://www.sciencedirect.com/science/article/pii/S0010218020301346&rt=
=3DAn+experimental+and+modeling+study+of+autoignition+characteristics+of+bu=
tanol/diesel+blends+over+wide+temperature+ranges&scisig=3DAAGBfm19DOLNm3-Fl=
WaO0trAxZkeidxYWg>

Using NMR spectroscopy to investigate the role played by copper in prion
diseases.
<http://scholar.google.com/scholar_url?url=3Dhttps://europepmc.org/article/=
med/32328835&hl=3Den&sa=3DX&d=3D16122276072657817806&scisig=3DAAGBfm1AE6Kyl=
jWO1k0f7oBnKFClEzhTMg&nossl=3D1&oi=3Dscholaralrt&hist=3Dv2Y_3P0AAAAJ:179499=
55323429043383:AAGBfm1nUe-t2q_4mKFiHSHFEAo0A4rRSA>
RA Alsiary, M Alghrably, A Saoudi, S Al-Ghamdi=E2=80=A6 - =E2=80=A6 and of =
the Italian
Society of =E2=80=A6, 2020
Prion diseases are a group of rare neurodegenerative disorders that develop
as a
result of the conformational conversion of normal prion protein (PrPC) to
the disease-
associated isoform (PrPSc). The mechanism that actually causes disease
remains =E2=80=A6
[image: Save]
<http://scholar.google.com/citations?update_op=3Demail_library_add&info=3Dz=
pCMKavUvd8J&citsig=3DAMD79ooAAAAAYImDx3r4gltEWBAkhl0g2POsXB9Qn4Lk&hl=3Den>
[image:
Twitter]
<http://scholar.google.com/scholar_share?hl=3Den&oi=3Dscholaralrt&ss=3Dtw&u=
rl=3Dhttps://europepmc.org/article/med/32328835&rt=3DUsing+NMR+spectroscopy=
+to+investigate+the+role+played+by+copper+in+prion+diseases.&scisig=3DAAGBf=
m1RidyRD-x2FOemP6iqCsr-6GAVKA>
[image:
Facebook]
<http://scholar.google.com/scholar_share?hl=3Den&oi=3Dscholaralrt&ss=3Dfb&u=
rl=3Dhttps://europepmc.org/article/med/32328835&rt=3DUsing+NMR+spectroscopy=
+to+investigate+the+role+played+by+copper+in+prion+diseases.&scisig=3DAAGBf=
m1RidyRD-x2FOemP6iqCsr-6GAVKA>


'''

regex = re.compile('(http://scholar.*?)&')
url_all = regex.findall(test_string)
citation_url = []
for i in url_all:
    if search('scholar.google.com',i):
        qs = parse_qs(urlparse(i).query).values()
        if search('http',str(qs[0])):
            citation_url.append(qs[0])
print citation_url

Present output

https://link.springer.com/content/pdf/10.1007/s11947-020-02461-6.pdf

Desired output

https://link.springer.com/content/pdf/10.1007/s11947-020-02461-6.pdf
https://www.sciencedirect.com/science/article/pii/S0010218020301346
https://europepmc.org/article/med/3232883

How to get handle URL text wrapping with equal sign and extracting the redirect URL in Python?

Answer 1

You could match either a question mark or ampersand [&?] using a character class. Looking at the example data, for the url= part, you can add optional newlines and an optional equals sign and adjust accordingly.

Some urls start with 3D, you can make that part optional using a non capturing group (?:3D)?

Then capture in group 1 matching http followed by matching all chars except &

\bhttp://scholar\.google\.com.*?[&?]\n?u=?\n?r\n?l\n?=(?:3D)?(http[^&]+)

Regex demo

Answer 2

see this regex pattern i think it might help to extract redirect uri

(http:\/\/scholar[\w.\/=&?]*)[?]?u[=]?rl=([\w\:.\/\-=]+)

also see this example here https://regex101.com/r/dmkF3h/3