Best way to parse a URL query string

Question

What is the best way to parse data out of a URL query string (for instance, data appended to the URL by a form) in python? My goal is to accept form data and display it on the same page. I've researched several methods that aren't quite what I'm looking for.

I'm creating a simple web server with the goal of learning about sockets. This web server won't be used for anything but testing purposes.

GET /?1pm=sample&2pm=&3pm=&4pm=&5pm= HTTP/1.1
Host: localhost:50000
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:11.0) Gecko/20100101 Firefox/11.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: keep-alive
Referer: http://localhost:50000/?1pm=sample&2pm=&3pm=&4pm=&5pm=

Answer 1

The urllib.parse module is your friend: https://docs.python.org/3/library/urllib.parse.html

Check out urllib.parse.parse_qs (parsing a query-string, i.e. form data sent to server by GET or form data posted by POST, at least for non-multipart data). There's also cgi.FieldStorage for interpreting multipart-data.

For parsing the rest of an HTTP interaction, see RFC2616, which is the HTTP/1.1 protocol specification.

Answer 2

Here is an example using python3 urllib.parse:

from urllib.parse import urlparse, parse_qs
URL='https://someurl.com/with/query_string?i=main&mode=front&sid=12ab&enc=+Hello'
parsed_url = urlparse(URL)
parse_qs(parsed_url.query)

output:

{'i': ['main'], 'enc': [' Hello '], 'mode': ['front'], 'sid': ['12ab']}

Note for python2: from urlparse import urlparse, parse_qs

SEE: https://pythonhosted.org/six/#module-six.moves.urllib.parse

Answer 3

If you need unique key from query string, use dict() with parse_qsl()

import urllib.parse
urllib.parse.urlparse('https://someurl.com/with/query_string?a=1&b=2&b=3').query
    a=1&b=2&b=3
urllib.parse.parse_qs('a=1&b=2&b=3');
    {'a': ['1'], 'b': ['2','3']}
urllib.parse.parse_qsl('a=1&b=2&b=3')
    [('a', '1'), ('b', '2'), ('b', '3')]
dict(urllib.parse.parse_qsl('a=1&b=2&b=3'))
    {'a': '1', 'b': '3'}