The new “walrus operator” in Python is written as := and has been the topic of much discussion. This post describes a few of Python’s other whimsically-named but less-well-known multi-character operators.

These operators are announced today, April 1, 2023, but, much like Dorothy with her ruby slippers, you always had the power to use them, you just had to learn it for yourself!

Ski Hat Operator

The “ski hat” operator is written as *=0 and can be used to empty out a variable, be it a list, string, tuple, or numeric value.

For example, after executing the following code, skiers is an empty list.

skiers = ["Lindsey", "Alberto", "Bode"]

skiers *=0

Dumbbell Operator

The “dumbbell operator” is written as [:]=[] and can also be used to empty a list, but is not as versatile as the ski hat operator, as it doesn’t work for most other types.

After executing the following code, reps will be an empty list:

reps = [1, 2, 3, 4, 5]

reps [:]=[]

Lapping Cat Operator

The “lapping cat” operator is written as ,= and picks out the first element of an iterable. Like a finicky cat, it complains if there are other bothersome elements in the iterable.

After executing the following code, water is 'HHO'.

water ,= ['H'*2+'O']

Starship Operator

The “starship” operator is written as , *_= and depicts a photon torpedo alongside a dual-nacelle starship (such as the Enterprise). It has a similar effect to the lapping cat operator in picking out the first element of an iterable, but it allows the iterable to have more than one element.

After executing the following code, NCC is 1:

NCC    , *_=    [1, 7, 0, 1]

Flying Saucer Operator

The “flying saucer” operator is written as --0-- and “beams up” an integer division, making it round up rather than round down. (I learned about it from Mark Dickinson.)

The following expression evaluates to 5, not 4:

--0--   42 // 10

Emphasis Operator

The “emphasis operator” is written by surrounding an integer-valued expression with asterisks and is used to emphasize the following sequence by repeating it. For example,

sigh = 3
['oh', 'good', 'grief', *sigh* '!']

evaluates to ['oh', 'good', 'grief', '!', '!', '!'].

Shocked Muppet Operator

The “shocked Muppet operator” depicts Beaker in a sideways view; it is written as [:-(0)] and has the effect of producing an empty sequence. For example, the following evaluates to an empty string:

"meep meep"   [:-(0)]

Factorial Operator

Math fans will be pleased to learn that the factorial operator n! has been partially incorporated into Python.

Unfortunately, the implementation is incomplete. But these unit tests all pass, so that’s good enough, right?

assert 0!=1
assert 3!=6
assert 4!=24
assert 5!=120
assert 6!=720
assert 7!=5040
assert 8!=40,320
assert 9!=362,880

Abstract keyword

Python also allows you to use the keyword abstract to indicate that a method of an abstract class must be implemented in a subclass for any instantiated object.

In the following code, the method name is defined as abstract, so a call to an object of the class results in an error message pointing out that the method is not defined.

class AnAbstractClass:
    def name(self): 
        abstract

>>> AnAbstractClass().name()
NameError: name 'abstract' is not defined

More

The astute reader will recognize that these new operators rely on the placement of spaces in a way that violates PEP 8.

To that I say: but my way is more fun! Especially today, April 1. For more operators, including implementations of the ++ and << operators from C++, see my old post.

PS: Everything in this post is true, except for “that’s good enough, right?”

Articles in this Series

April 1, 2016: Go, Dog. Gauguin! The P. D. Eastman Story
April 1, 2017: Last Tweets of the Krell
April 1, 2018: Functional Lifestyles
April 1, 2020: Hope I Incorporate Before I Get Old
April 1, 2021: Hamilton: The Mathematical Musical
April 1, 2023: Packet-Switching Patent Revealed!
April 1, 2023: New Python Operators!

Today a previously secret patent filing by Amazon.com Inc. was uncovered. To quote from the patent:

This invention relates to a packet-switching network, and more particularly to a method for routing physical packets through a packet-switched network.

A conventional packet-switched delivery system typically includes a plurality of interconnected node elements, each of which includes a processor capable of receiving, routing, and forwarding packets along at least one link. The processor of each node element is typically responsible for locating the destination address of a given packet and establishing a route from the source to the destination address. A route through the network thus created may comprise several nodes and it may include intermediate routing nodes at which packets are temporarily stored for further processing.

The present invention provides a peer-to-peer means for routing physical packets through a dynamic packet-switched network in a more efficient manner than conventional methods. Specifically, the present invention comprises a method wherein participating node elements (automobiles, labeled “A” in Figure 1) will broadcast their current planned route to nearby nodes. Based upon this information, the method determines a route through the network that delivers the packet to its destination.

Packets are initially loaded into a node’s basket (labeled “B” in Figure 1) and whenever a node is in immediate proximity of another node whose broadcasted route will bring it closer to the package’s destination, the first node will use a Car Augmentation Top-mounted Automated Package Upload and Transfer Tool (or CATAPULT, labeled “C” in Figure 1) to transfer the package to the basket (“B”) of the second node. Through its use of efficient routing, the present invention streamlines the packet delivery process, thus improving overall performance and reliability.

The patent appears to be an innovative way to reduce transportation costs and pollution (as well as pesky labor disputes) by replacing delivery trucks and drivers with a peer-to-peer network of customers who were already on the road anyway, and collectively were driving to the places the packets need to go.

Since packet loss would be a considerable negative, it is expected that the TCP protocol with the synchronize-acknowledge handshake will be used rather than the UDP protocol.

Below is a depiction of packet-switching in action:

Articles in this Series

April 1 2016: Go, Dog. Gauguin! The P. D. Eastman Story
April 1 2017: Last Tweets of the Krell
April 1 2018: Functional Lifestyles
April 1 2020: Hope I Incorporate Before I Get Old
April 1 2021: Hamilton: The Mathematical Musical
April 1 2023: Packet-Switching Patent Revealed!
April 1 2023: New Python Operators!

That’s so unfair–with all due respect to Lin-Manuel Miranda, nobody has written a musical about William Rowan Hamilton, the 19th century Irish mathematician. Today, April 1st 2021, I’m sharing parts of three songs from this highly original musical.

William Rowan Hamilton was a child prodigy in mathematics, linguistics, physics, and astronomy.

William Rowan Hamilton

How does the 4th of 9 children, son of a solicitor Scotsman, dropped in the middle of a forgotten
spot in Talbots Castle in a town that’s smaller
grow up to be a hero and a scholar?

The mathematician on a mission, sent away by his father
got a lot farther by working a lot harder
by being a lot smarter by climbing up the rungs
by thirteen, he knew a dozen tongues.

Well the word got around they said this kid has knowledge
took up a collection just to send him to Trinity College.
Get your education don’t forget from whence you came. And the world is gonna know your name.
What’s ya name, man?

William Rowan Hamilton.
My name is William Rowan Hamilton.
And there’s a million things I haven’t done.
But just you wait, just you, wait.

Hamilton was a pioneer in graph theory, the branch of mathematics concerning connections between things. Every time your UPS or DoorDash or Amazon driver makes a series of deliveries to different locations, that’s a Hamiltonian Path, and the deliveries are more efficient thanks to Hamilton’s work.

I’m Not Throwing Away My Path

I am not throwing away my path!
I am not throwing away my path!
Hey yo, I’m just like my graph
I’m multiply connected, don’t laugh
And I’m not throwing away my path!
I’m ‘a get a scholarship to Trinity College
I prob’ly shouldn’t brag, but I got the fire and
I’m the Royal Astronomer of Ireland
Only eighteen but my mind is older
These Dublin streets get colder, I pledge
Ev’ry vertex, ev’ry edge
I have learned to manage, I don’t have disciples
I walk these graphs in cycles
But I am not throwing away
My path
I am not throwing away
My path

Hamilton invented the quaternion number system, which can be used to represent the position of objects in three-dimensional space, the direction they are pointing, and most importantly the way they rotate. This number system is used today in computer graphics–Buzz Lightyear and Woody are described by quaternions–and in video games such as Assassin’s Creed and Kerbal Space Program. Quaternions are used by industrial robots that have several arm joints that must all rotate in smooth unison. And NASA uses quaternions to accurately chart the flight paths of spacecraft through the solar system.

The Vector Where it Happened

The quaternion emerges as an unprecedented multiplicative pearl
A system he can rotate however he wants
The del operator emerges with div, grad, and curl
And here’s the pièce de résistance:
No other numbers are in
The vector where it happened
The vector where it happened
The vector where it happened
No other numbers are in
The vector where it happened
The vector where it happened
The vector where it happened
No one really knows what i, j, and k mean
The math is so clean
How they depict a scene
We just assume that it happens
But no other numbers are in
The vector where it happens.

Articles in this Series

April 1 2016: Go, Dog. Gauguin! The P. D. Eastman Story
April 1 2017: Last Tweets of the Krell
April 1 2018: Functional Lifestyles
April 1 2020: Hope I Incorporate Before I Get Old
April 1 2021: Hamilton: The Mathematical Musical
April 1 2023: Packet-Switching Patent Revealed!
April 1 2023: New Python Operators!

In the 1970’s we thought that our rock and roll icons were leading a revolution against the establishment, and we the fans were part of it. But in 2020, when I see that a Wealth Management company sponsored the Rolling Stones tour and Cadillac has a Led Zeppelin theme song, I realize we’ve all become the bourgeois. So here are some suggested lyric changes for future tours:

The Who

Things they do look awful c-c-c-cold
I hope I incorporate before I get old
To avoid my taxation
To avoid my taxation, baby

The Police

Roxanne
You don’t have to put on the red ink
Those days are over
You don’t have to sell your IRA bonds

Thin Lizzy

Guess who just got back today
Them CPAs that had been away
Foreign junket got them a tax defray
But man, I still think them cats are crazy

The Boss

Oh, so your daddy says he knows that I don’t have any money
Well, tell him this is his last chance to get his daughter in a fine romance
Because a reinsurance company, Rosie, just gave me a big advance
Prices were slashed and the Dow almost crashed, but the Lord had mercy
Xerox machine, she’s a dud, copies are like mud
Somewhere in the office parks of Jersey

The Clash

Darling you got to let me know
Should I check the box in this row?
If you say you are my dear
I’ll be here through the fiscal year
So you got to give me instruction
Should I take you as a tax deduction?

Steppenwolf

Like a culturally privileged child
We were born, born to be mild
We started out so high
We hardly had to try
Born to be mild
Born to be mild

(And if you don’t recognize the songs, congrats! You’re not part of the aging demographic.)

Articles in this Series

April 1 2016: Go, Dog. Gauguin! The P. D. Eastman Story
April 1 2017: Last Tweets of the Krell
April 1 2018: Functional Lifestyles
April 1 2020: Hope I Incorporate Before I Get Old
April 1 2021: Hamilton: The Mathematical Musical
April 1 2023: Packet-Switching Patent Revealed!
April 1 2023: New Python Operators!

so I wrote down these lyrics:

I’ve Consed Every Pair

I was totin’ my laptop at a trendy Palo Alto cafe
When I passed a hacker bro’ with a new 16 inch display
“If you’re goin’ to be hacking, Mack, at my table you can rest”
And so I climbed into a seat and then I started up a test
He asked me if I’d programmed with the Clojure brand
And I said, “Listen, I’ve used every repl in this here land”

I’ve consed every pair, man
I’ve consed every pair, man
Signaled every err, man
I’ve done so much software, man
Of repls I’ve a’had my share, man
I’ve consed every pair

I’ve used Franz Lisp, LM Lisp, Common Lisp, PLT
MacLisp, ZetaLisp, Emacs Lisp, and Yale’s T
Vaxen, Explorer, Symbolics, PDP
Sun station, PC, MacBook, Blackberry
Racket, Pyret, JScheme, R7
R6, R5, R4, I’m in heaven

I’ve consed every pair, man
I’ve consed every pair, man
Signaled every err, man
I’ve done so much software, man
Of repls I’ve a’had my share, man
I’ve consed every pair

I’ve used deftype, ftype, machine-type, define
lisp-type, typecase, check-type, read-line
class-name, class-of, defclass, load-time
base-string, write-string, string-trim, run-time
make-list, make-hash, make-node, string-make
make-array, display, two-way, for Pete’s sake

I’ve consed every pair, man
I’ve consed every pair, man
Signaled every err, man
I’ve done so much software, man
Of repls I’ve a’had my share, man
I’ve consed every pair

I’ve used arrayp, boundp, minusp, iterator
constantp, equalp, typep, numerator
bit-nor, vector, ffloor, butlast,
special or, xor, err-or, broadcast,
truncate, conjugate, concatenate, package-error,
allocate, update, random-state, what a terror.

I’ve consed every pair, man
I’ve consed every pair, man
Signaled every err, man
I’ve done so much software, man
Of repls I’ve a’had my share, man
I’ve consed every pair

Q: Miranda, can you tell us the philosophy of Functional Lifestyles?

A: Functional Lifestyles is dedicated to making our clients stronger, slimmer, healthier, more robust, more concise, more elegant, and better able to multitask, by introducing them to a pure functional lifestyle, and weaning them from the imperative lifestyle. We offer a one-on-one personalized experience; we’ll always call you by name.

Q: What should I expect in my first workout?

A: First we’d do some folds, both to the left and to the right. Such a great way to reduce! Then, for strength: lambda lifting. Many clients have inadvertently put on a few unwanted free variables, and lambda lifting will reduce that dramatically. Usually we can slim down even more with some lambda drops.

Q: Is this for anybody?

A: Absolutely! No matter how eager or lazy you are, we’ve got an evaluation strategy for you. And we have structures for all forms; whether you’re an endomorph, an isomorph, or a homomorph, we’ve got the mapping for you. It is completely safe — no side effects whatsoever. And if you’ve got multiple concurrent problems, we can help you reach clojure.

Q: Can the training become almost a religious experience?

A: I wouldn’t say that. At Functional Lifestyles we believe in a strict separation of Church and state.

Q: I’ve heard that some people who get hooked on the functional lifestyle find it hard to communicate with their non-functional friends?

A: Not at all! We’ll set you up with monads that will allow you to do all the input and output you want, and even handle exceptions!

Q: So would you say that your training will change me for the better?

A: Oh for Milner’s sake, no! We consider all our clients to be immutable. What we do guarantee is that the application of our functions will produce a new and improved version of you.

Q: Isn’t that basically the same thing?

A: OK, you’ve got a lot to learn. Let’s get started!

Articles in this Series

April 1 2016: Go, Dog. Gauguin! The P. D. Eastman Story
April 1 2017: Last Tweets of the Krell
April 1 2018: Functional Lifestyles
April 1 2020: Hope I Incorporate Before I Get Old
April 1 2021: Hamilton: The Mathematical Musical
April 1 2023: Packet-Switching Patent Revealed!
April 1 2023: New Python Operators!

But on April 1, researchers from the OpenNMT institute announced a stunning success in translating previously undecipherable Krell messages, thanks to deep neural machine translation technology.

They note that the Krell language has three grammatical pluractionality markers, one for public speech addressed to everyone, one for cohort speech among a group of peers, and one for private speech between individuals. The researchers joked that these modes correspond to our Twitter, Slack, and text messaging. Krell names are unpronounceable for us, so we have chosen single-letter initials for the participants.

The Participants

P: The president of an organization that we will translate as KrellTech.
A: The alpha technical expert at KrellTech.
S: A site reliability engineer.
X: A user experience designer.

The Messages

P(to public) KrellTech is thrilled to announce this morning the launch of CognoMaterializer 1.0! The basic version of this service is available free of charge to all citizens of Altair IV. The possibilities are equal to the number ten raised almost literally to the power of infinity!

P(to cohort) Time to party! All KrellTech employees, friends, and family invited to the big bash at the Level 700 meeting room.

P(to cohort) Congratulations everyone, and special thanks to A for leading this project. Never have I seen a single individual successfully do so much, on their own, to create a complex project like this! The drinks are on me, A!

A(to cohort) Thanks, P! I’ll toast you for one drink but then I’ll have to crash — too many late nights bringing this project home! I’m fried!

Later That Night

P(to public) After midnight … we start day two of the CognoMaterializer era. A few reports of problems, due to user error. I promise we will have a fix by tomorrow for all affected users!

S (to cohort) @A, you better get in here fast. Some of these user reports look serious …

S (to cohort) @A, WHERE ARE YOU!!?? You don’t respond to messages, pages, or calls. I’m going to start a rollback to the previous version.

S (to cohort) @A, or @X, or anyone in @cognoteam, what’s up with the rollback script??? I tried to run it, and it just gave an error message.

X(to cohort) @A, why do you have unreviewed code from experimental running in production? I didn’t even know that was possible!!??

X(to cohort) I warned everyone not to cut the budget for user testing, but did you listen? Noooo, @P said we had no budget left. We brought a few users in for one-hour tests, but we never did the week-long home tests I specified as essential. We’re going to have to pull the plug on this whole thing.

S(to cohort) I tried the shutdown script, but the ping-and-restart daemons restart the servers faster than I can shut them down. Didn’t anyone try this before?? Can we contact our brick service provider and have them shut it down? Could we run around and pull all the plugs?

X(to cohort) umm, the brick is a 8000 cubic mile array of klystron relays powered by 9,200 thermonuclear reactors. I don’t think we can do a manual shutdown.

P (to public) Everyone, we’ve got a few minor issues — I recommend taking a pause from enjoying the CognoMaterializer until we get a quick update out. Just try not to think about anything bad. Or anything at all, really. And whatever you do, don’t go to sleep!!

X(to cohort) we’re 3-way-copulated

S (to cohort) we’re triple-3-way-copulated

Last Known Krell Message

S(to public) this is so bad … I don’t know if there is anyone left out there to see this. I’m sorry for the damage we’ve done to our civilization; I know we could have protected it if we had followed these practices:

• Many eyes. Don’t let one person work alone. All changes should be reviewed and approved by others.
• Understand use cases. The temptation is to concentrate on what you, as an engineer, do in building your service, but the truly important thing is what your customers will do when they use it.
• Engineers are judged by failure. Product designers are judged by how useful the product is when it is functioning. Engineers are judged by how gracefully the system degrades when it fails.
• Test what you build and build what you test. Make sure the use cases are tested, and that what you run is what was tested. Hermetic builds assure that you know where everything came from, and can reproduce it.
• Adversarial testing. Be devious in imagining what could go wrong, and fix it before it does. Hire red teams to try to uncover vulnerabilities.
• Software Release Checklist. Don’t release until you check every box: code coverage and tests passing; bugs fixed; feature checklist; security review; privacy review; fairness review; accessibility review; performance review; documentation review; whatever else is part of your development process. Yes, sometimes you will release software with known bugs, but that should always be part of an intentional decision to do so.
• Product Launch Checklist. Engineers often have the mindset of “if the software works, ship it.” But working code by itself is not a product. Before launching, have a checklist for the whole product: sales, marketing, communication, and support teams have to be trained and ready to go.
• Landing Checklist. Everyone remembers the date that our species first landed on our moon–the day they landed, not the day they launched. So it is with software; prepare for the landing, when the software is in the hands of many customers, not just for the launch, when it is in the hands of a few enthusiastic early adopters.
• Progressive rollouts. Trial the system with a small number of users before releasing to a large number.
• Monitor. Have enough people, and automatic systems, to gather feedback on how you are doing and sound an alert when there are problems.
• On Call: Make sure there is a schedule of qualified people on call to deal with problems, especially at the start and after any major change.
• Instant shut down and rollback. Make sure you have the ability to cleanly shut down the system if something goes wrong, and in case of error to roll back to the previous working system. Bonus points if you can selectively cherry pick properly-working improvements and reliably add them to a previous version.
• Safe User Interface. Make it hard for users to do unsafe things. P insisted on a “one-thought” interface (and even patented it). It is safer to require a specific prompt to initiate action (“OK, Cogno”), to have the system echo back its interpretation of the user’s command, and to use a confirmation dialog for actions with big irreversible effects (“Are you sure you want to conjure a Monster from the Id?”).
• Culture. X and I (and others) had concerns all along, but the culture encouraged us to keep quiet about problems, discouraged discussion, and didn’t have a process to fix the problems.
• Practice emergencies. Don’t wait until a real emergency to see how good your response is; practice in advance.
• Premortems. Before launch, ask everyone on the team “Imagine the project turns out to be a miserable failure. What could have caused that?” Then fix the problems before they happen.
• Postmortems. When something goes wrong, analyze and understand it after the fact … that is, if there is anyone left alive.

Articles in this Series

April 1 2016: Go, Dog. Gauguin! The P. D. Eastman Story
April 1 2017: Last Tweets of the Krell
April 1 2018: Functional Lifestyles
April 1 2020: Hope I Incorporate Before I Get Old
April 1 2021: Hamilton: The Mathematical Musical
April 1 2023: Packet-Switching Patent Revealed!
April 1 2023: New Python Operators!

I always assumed that P. D. Eastman was a typical American man living a Mad Men existence in the 50s and 60s, turning out children’s books for a living. (Or maybe, like Wallace Stevens, as a diversion from his day job at an insurance agency.)

But in a fascinating exhibit opening April 1 at the National Center for Children’s Illustrated Literature, the truth was revealed for the first time. It turns out that “P. D. Eastman” is actually a pseudonym that joins two men, separated by two generations and 5,000 miles, but joined by family ties and an enduring secret.

Philippe Delano Homme d’Est was a French artist, born in 1849, and best known for his Art Nouveau illustrations in Quartier Latin. Philippe was befriended by Paul Gauguin, and in 1891 they emigrated together to Tahiti. For several years they both thrived there. Philippe tried to convince Gauguin to join him in a bizarre project: a book that incorporated ideas from Soren Kirkegaard’s existential philosophy, but was presented as an illustrated children’s book. The NCCIL exhibit shows draft pages from the book in Pierre’s hand asking the questions “D’où Venons Nous / Que Sommes Nous / Où sont ces chiens va / Que vont-ils faire” (Where Do We Come From? / What Are We? / Where Are Those Dogs Going? / What Are They Going to Do?) and answering with “À l’arbre! Jusqu’à l’arbre!” (To the tree! Up the tree!). The surviving illustrations demonstrate an obvious clash of styles between the two collaborating artists:

Eventually the pair had a falling out. Gauguin wanted to present his paintings without the juvenile story-telling. Philippe never forgave Gauguin, and returned to France, where he was able to produce a galley proof of his book, but the publisher eventually declined to produce it, and Philippe died frustrated and disappointed in 1921.

Philippe’s grandson, Philip, inherited a locked box of his grandfather’s artwork, with instructions that it not be opened for 30 years. In 1951 Philip opened the box, and set about to realize his grandfather’s dream of publishing, using the assumed name “P. D. Eastman.” Philip fils was a better story-teller than Philippe père, and was competent enough as an artist to emulate and extend his grandfather’s style. As the NCCIL exhibit demonstrates, the first three books under P. D. Eastman’s name were patched together from his grandfather’s collection of sketches, but after that, the stories and illustrations were all from Philip, with an occasional character borrowed from Philippe’s sketchbook. In deference to his grandfather’s wishes, Philip himself never discussed the origins of the work, and instead locked everything up with instructions that his box too was not to be opened until 30 years after his death. And so it was that on January 7, 2016, the link between Gauguin and Eastman was rediscovered, and with the opening of the exhibit this April 1, it was finally revealed to the world.

Articles in this Series

April 1 2016: Go, Dog. Gauguin! The P. D. Eastman Story
April 1 2017: Last Tweets of the Krell
April 1 2018: Functional Lifestyles
April 1 2020: Hope I Incorporate Before I Get Old
April 1 2021: Hamilton: The Mathematical Musical
April 1 2023: Packet-Switching Patent Revealed!
April 1 2023: New Python Operators!

Addendum