I used regex in a meaningful way for the first time yesterday.

Regex is short for Regular Expressions and are used to define search/match patterns in programming. For example, Python has the re standard library module which can be used to construct regular expressions and use them to match/search strings.

I have known of regular expressions for a while now but I have never actually used them in any meaningful way. Until yesterday.

I've been working on trivial contributions to open source Python projects. One of the trivial changes was updating how the super builtin function is called. On Python 3, arguments are optional. On Python 2, arguments have to be passed and specifically, super(ClassName, self) is how the builtin function needs to be called.

For Python packages that are completely dropping support for Python 2, they can get rid of the old way of calling super. But, manually finding and updating the usage is a little tedious, especially for large codebases which heavily rely on objects and inheritance.

This is the perfect place where regex shines. As I mentioned above, I can define all uses of super on Python 2 using super(ClassName, self) and I can just update that to super().

I used the online regex editor regex101 to experiment with building the regular expression and I ended up with (super)+\(+(\w+)(,)+\s(self)+\)+.

Let's break it down.

  • (super)+ - I am being lenient in saying that there can be one or more exact matches of "super"
  • \(+ - One or more matches of "("
  • (\w+) - One or more words
  • (,)+ - One or more ","
  • \s - One whitespace character
  • (self)+ - One or more "self"
  • \)+ - One or more ")"

Note that I could have constructed a stricter/better regular expression. I am expecting the codebase to conform to PEP8 when I say that there should be a "," after the word and exactly one whitespace after "," and before "self". But, this works and it works well for my needs.

And this led to a Pull Request on Traits.

Popular posts from this blog

Animation using GNUPlot

Image
Animation using GNUPlot I've been trying to create an animation depicting a quasar spectrum moving across the 5 SDSS pass bands with respect to redshift. It is important to visualise what emission lines are moving in and out of bands to be able to understand the color-redshift plots and the changes in it. I've tried doing this using the animate function in matplotlib, python but i wasn't able to make it work - meaning i worked on it for a couple of days and then i gave up, not having found solutions for my problems on the internet. And then i came across this site, where the gunn-peterson trough and the lyman alpha forest have been depicted - in a beautiful manner. And this got me interested in using js and d3 to do the animations and make it dynamic - using sliders etc. In the meanwhile, i thought i'd look up and see if there was a way to create animations in gnuplot and whoopdedoo, what do i find but nirvana! In the image, you see 5 static curv
Read more

Thoughts on the National Deep Tech Startup Policy

The Principal Scientific Advisor to the Government of India published a draft policy to support and nurtue the unique requirements of Deep Tech startups in India. I just finished reading it and put together a few comments in a FOSS United forum thread . I will probably read it again a week or so later and try to update my comments on the thread with any new insights/thoughts I have.
Read more

Arxiv author affiliations using Python

So, I wanted to get author affiliation information from papers on arXiv. arXiv provides with an API to bulk query their database and get information. Following that, I look for the attribute 'arxiv:affiliation' in the html data. Here's the code - import urllib from BeautifulSoup import BeautifulStoneSoup   url = 'http://export.arxiv.org/api/query?search_query=all:astro&start=0&max_results=1000'   data = urllib.urlopen(url).read() soup = BeautifulStoneSoup(data) #print(soup.prettify()) #list = soup.findAll('arxiv:affiliation') #for i in range(len(list)): #        print list[i].contents   test = [tag.string for tag in soup.findAll('arxiv:aiffiliation')] Now, the problem I'm having is that I'm getting affiliation of all authors which I want to split into sets of affiliations of authors of a paper, which I'm stuck on at the moment. Once I get that part, I can move on to the next part of this pet project, displaying these
Read more