Perl Programmer's Guide to Python

Those who know me may want to sit down for this. It will come as a shock that I have decided to enter the 21st century and learn Python.

I know, I feel like some kind of traitor. But it's time to face facts: while reports of Perl's death are greatly exaggerated; clearly, the only people writing *new* Perl code are dinosaurs like me.

Anyway, this post is NOT a Perl programmer's guide to Python. It is a question for the Internet if such a guide would be appreciated. I found [one](https://everythingsysadmin.com/perl2python.html) that's OK, but I was hoping for more.

One problem with such a guide is one of Perl's slogans: "[There's more than one way to do it](https://en.wikipedia.org/wiki/Perl#Philosophy)". I doubt many other Perl programmers use Perl the way I do. I suspect that a real Perl programmer would look at my code and say, "Oh look! A C programmer!" While I might look at code written by a real Perl programmer and say, "Oh look! Line noise!" Anyway, my point is that my Perl Programmer's Guide to Python is likely to be of little help to another Perl programmer.

So anyway, if any of my thousands of readers would be interested in such a guide, let me know.

Update: interesting. I found PerlPhrasebook on the official Python site. I didn't look at it carefully, but I did get a bad first impression. The String Interpolation section does not mention "f-strings" the Python f"bar{foo}" construct, which is clearly the closest analog to Perl's string interpolation. F-strings were introduced 7 years ago (2017), so the PerlPhrasebook has apparently not been updated since then. Acutally, I just checked - it was last updated in 2012. Maybe this suggests that not many people use that document any more? I.e. all Perl programmers who are likely to migrate to Python have already done so? This suggests that maybe writing my own guide is pointless. (Not that pointlessness has ever stopped me from doing something.)

Python and Perl and Bash (oh my!)

I've been thinking a lot recently about code maintainability, including scripts. I write a lot of shell scripts, usually restricting myself to Bourne shell features, not GNU Bash extensions. I also write a lot of Perl scripts, mostly because I'm a thousand years old, and back then, Perl was the state of the scripting art.

Anyway, it's not unusual for me to write a shell script that invokes Perl to do some regular expression magic. For example, I recently wanted to take a dotted IP address (e.g. "10.29.3.4") and convert it into a string of 8 hexadecimal digits representing the network order binary representation of the same (i.e. "0a1d0304"). My kneejerk reaction is this:

HEX=`echo "10.29.3.4" | perl -nle 'if (/^(\d+)\.(\d+)\.(\d+)\.(\d+)$/) { printf("%02x%02x%02x%02x\n", $1, $2, $3, $4) } else {die "invalid IP $_\n"'}`

But since maintainability has been on my mind lately, most programmers (especially younger ones) would have a steep Perl learning curve to maintain that. So my second thought was to do it in Bash directly. I haven't done much regular expression processing in Bash, given my habit of staying within Bourne, but really, that habit has outlived its usefulness. Open-source Unix (Linux and Berkley) have relegated other Unixes to rare niche use cases, and even those other Unixes have a way to download Bash. I should just accept that Bash extensions are fair game. Here's my second try:

pattern='^([0-9]+)\.([0-9]+)\.([0-9]+)\.([0-9]+)$'
if [[ "$MCAST_ADDR" =~ $pattern ]]; then
  GRP_HEX=$(printf '%02x%02x%02x%02x' ${BASH_REMATCH[1]} ${BASH_REMATCH[2]} ${BASH_REMATCH[3]} ${BASH_REMATCH[4]})
else echo "invalid IP addr"; exit 1
fi

But even as I feel fairly confident that more programmers would be able to maintain that than the Perl version, I still realize that the vast majority of programmers I've known have very basic shell scripting skills. I'm not sure the Bash version expands the pool of qualified maintainers by much. I think the best that can be said is that a programmer with basic shell scripting skills can learn regular expression matching in Bash a lot faster than learning enough Perl to do it.

So, how about Python?

Well, with some help from Claude, here's a Python one-liner:

HEX=`python3 -c "import sys, ipaddress; print('{:08x}'.format(int(ipaddress.ip_address(sys.argv[1]))))" 10.29.2.3`

So, not only does this use a language that many programmers know, it also completely avoids regular expressions, which is another uncommon skill among the programmers I've known.

*sigh*

What's a dinosaur to do? I haven't been paid to be a programmer for a lot of years, so the programming I do is mostly for my own entertainment. And dammit, I *like* Perl! I've done enough Python programming to know that ... I just don't like it that much. And let's face it: the code I write is unlikely to be widely used, so who cares about maintainability?

(pause for effect)

I do.

I have standards on how programming should be done. If programming is now largely my hobby, I get the most personal reward by doing it according to my standards. I think it's time for me to say a fond farewell to Perl and bow down to my Python overlords.