Robotparser doesn't support two quite important optional parameters from the robots.txt file. I have implemented those in the following way:
(Robotparser should be initialized in the usual way:
rp = robotparser.RobotFileParser()
rp.set_url(..)
rp.read
)

crawl_delay(useragent) - Returns time in seconds that you need to wait for crawling
if none is specified, or doesn't apply to this user agent, returns -1
request_rate(useragent) - Returns a list in the form [request,seconds].
if none is specified, or doesn't apply to this user agent, returns -1

Thanks for the patch. New features must be implemented in Python 3.4. Python 2.7 is in feature freeze mode and therefore doesn't get new features.

Okay, sorry didn't know that (:
Here's the same patch (Same functionality) for python3

Feedback is welcome, as always (:

We have a team that mentors new contributors. If you are interested to get your patch into Python 3.4, please read http://pythonmentors.com/ . The people are really friendly and will help you with every step of the process.

Okay, here's a proper patch with documentation entry and test cases.
Please review and comment

Reformatted patch

Hey,
it has been more than an year since the last activity. 
Is there anything else I should do in order for someone of the python devs team to review my changes and perhaps give some feedback?

Nick

I left a few comments on Rietveld.

Thank you for the review!
I have addressed your comments and release a v2 of the patch:
Highlights:
 No longer crashes when provided with malformed crawl-delay/robots.txt parameter.
 Returns None when parameter is missing or syntax is invalid.
 Simplified several functions.
 Extended tests.

http://bugs.python.org/review/16099/diff/6206/Doc/library/urllib.robotparser.rst
File Doc/library/urllib.robotparser.rst (right):

http://bugs.python.org/review/16099/diff/6206/Doc/library/urllib.robotparser....
Doc/library/urllib.robotparser.rst:56: .. method:: crawl_delay(useragent)
On 2013/12/09 03:30:54, berkerpeksag wrote:
> Is crawl_delay used for search engines? Google recommends you to set crawl speed
> via Google Webmaster Tools instead.
> 
> See https://support.google.com/webmasters/answer/48620?hl=en.
 
Crawl delay and request rate parameters are targeted to custom crawlers that many people/companies write for specific tasks. The Google webmaster tools is targeted only to google's crawler and typically web admins have different rates for google/yahoo/bing and all other user agents.

http://bugs.python.org/review/16099/diff/6206/Lib/urllib/robotparser.py
File Lib/urllib/robotparser.py (right):

http://bugs.python.org/review/16099/diff/6206/Lib/urllib/robotparser.py#newco...
Lib/urllib/robotparser.py:168: for entry in self.entries:
On 2013/12/09 03:30:54, berkerpeksag wrote:
> Is there a better way to calculate this? (perhaps O(1)?)

I have followed the model of what was written beforehand. A 0(1) implementation (probably based on dictionaries) would require a complete rewrite of this library, as all previously implemented functions employ the:
for entry in self.entries:
    if entry.applies_to(useragent):

logic. I don't think this matters particularly here, as those two functions in particular need only be called once per domain and robots.txt seldom contains more than 3 entries. This is why I have just followed the design laid out by the original developer.

Thanks

Nick

Oh... Sorry for the spam, could you please verify my documentation link syntax. I'm not entirely sure I got it right.

Hey,

Just a reminder friendly reminder that there hasn't been any activity for a month and I have released a v2, pending for review (:

Updated patch, all comments addressed, sorry for the 6 months delay. Please review

Hey,

Just a friendly reminder that there has been no activity for a month and a half and v3 is pending for review (:

Hey,

Just a friendly reminder that the patch is pending for review and there has been no activity for 3 months (:

Hey,

Friendly reminder that there has been no activity on this issue for more than an year.

Cheers,

Nick

New changeset dbed7cacfb7e by Berker Peksag in branch 'default':
Issue #16099: RobotFileParser now supports Crawl-delay and Request-rate
https://hg.python.org/cpython/rev/dbed7cacfb7e

I've finally committed your patch to default. Thank you for not giving up, Nikolay :)

Note that currently the link in the example section doesn't work. I will open a new issue for that.