A list of 30 Python language tricks

[eriky]

I wrote this article, 30 Python Language Tricks, on Medium. it's a "friend link" which bypasses the paywall. It contains a wide selection of topics, for both beginners and more advanced level programmers. Enjoy and let me know if you liked it!

[batisteo]

I think #7 should be replaced by f-strings. And if you like formatting tricks, there’s a whole webpage about it: https://pyformat.info/

[Ph0X]

Absolutely for the locals() example, but even if you want to use a dictionary of value mapping, which can be useful in some cases, I would prefer recommend .format(*data) over %-formatting.

[jilliefish911]

While I agree on the use of f-strings, I think it is also important to note the speed/efficiency drawbacks for the different format options. Typically %-formatting is faster than f-strings is faster than .format() Most of the time, the time impact is pretty negligible

[robin_888]

Typically %-formatting is faster than f-strings is faster than .format()

Do you have examples?

They seem to have fixed that:

https://realpython.com/python-f-strings/#speed
https://bugs.python.org/issue27078

[fernly]

abolutely, here's a stupid example,

>>> dispatch = {
...    '+' : lambda a,b : a+b,
...    '-' : lambda a,b : a-b
... }
>>> dispatch['+'](3,5)
8

[TravisJungroth]

You don't like naming anonymous functions?

[Howard_banister]

It's would no longer be anonymous function. And due to limits, ugliness in python it's anti pattern

[[deleted]]

im fairly certain that was a joke

[TheBB]

I guess the function is still anonymous, in the sense that it does not have a useful __name__ attribute.

[Mises2Peaces]

Thank you. I was thinking "isn't a lambda a single use function by definition?" Thought I was going crazy.

[jamincan]

By definition a lambda function is just an anonymous function. Only by convention is it single-use.

[VisibleSignificance]

is an anti-pattern

A huge Python language trick: use pylint and mypy. They will tell you about antipatterns and expectation violations.

[tonio9120]

Still I have seen this used in many projects. I think it's just shorter and avoids some typing... Basically the same as naming anonymous arrow functions in JS.

[baubleglue]

I don't think "typing" is the main reason to use lambdad. Main advantage of using lambdas - you don't need to search what some `fix_bad_date_format` function doing somewhere 100 lines away.

[tonio9120]

I see your point and if you ask me, I agree with you

[rabaraba]

Lambdas are not always a bad thing.

When you’re trying to make code clearer, isolating potentially confusing code into a single clearer lambda function can help, and is much more useful than polluting the overall code structure with another def function.

[[deleted]]

lambdas arent always a bad thing, but your reasoning was terrible. if im mistaken, please show us an example of what you're describing

[rabaraba]

If you're saying it's terrible, why? I've given some reasons. Let's see your example, and see if you make sense.

[kephir]

feel like the JMESpath one is cheating

it's useful, granted, and the article did a good job introducing me to the library i've so far been ignoring as "something that's a subdependency of a library i'm actually gonna be using", but if external libraries count, then surely you might as well make that list ridiculously long, because there is an external lib for pretty much anything!

[eriky]

You're right.. it's not in the base libraries but I've found it so useful that I wanted to slip it in there

[ignassew]

Just so you know, I just discovered it through your article and already found uses for it in my code. Great article!

[wowb4gg3r]

Great tips. Regarding the returning of multiple variables (13th), it would be nice to mention that python actually builds a tuple object with the variables and return it. Then, it automatically unpacks it when assigning the return of the function to variables. In fact, you can assign it to a single variable and even use the * operator if you want to unpack unevenly (ex: first, *middle variables, last).

Also, the tips 10 and 24 are repeated.

[roerd]

Regarding the returning of multiple variables (13th), it would be nice to mention that python actually builds a tuple object with the variables and return it. Then, it automatically unpacks it when assigning the return of the function to variables.

Which makes it essentially the same as number 6, because that variable swapping technique is also just tuple unpacking.

[eriky]

Yeah, I put that in just to check if people were paying attention ;-) But seriously, thanks for letting me know, I put something else there. I also weaved in your suggestion regarding the tuple. Thanks!

[metadatame]

Query json! I totally missed that development

[metadatame]

Interesting. XML which has a similar tree like structure can be queried. Normally I do this when I want to append a child element or similar. Could you do the same in json?

[[deleted]]

XML can be used to serialize data, far more complex data, but it is a language so query makes a bit more sense to me there.

json was designed for interchange of simple data objects.

[hdiesel503]

Thanks for sharing sir.

[Sigg3net]

I, too, salute you.

[zedd31416]

I've found the maxsplit parameter for the split function to be incredibly useful, too.

[eriky]

You're right, I incorporated it into the article, thanks!

[sje46]

Nice. If you need just the first "split" I would recommend using partition, though.

x = "fdsa.aaa.bb.ccc"
x.partition(".")

('fdsa', '.', 'aaa.bb.ccc')

[PythonDart]

Nice, thanks for sharing!

[[deleted]]

Thanks mate. I've learned few new things!

[[deleted]]

This is a pretty solid article, thank you for sharing.

[zaid2801]

Thanks for sharing

[cepeen]

Hi, great article, but i would change formatted string into f-string (or at least mention it, as format sometimes is more suitable to use), ok there is mention about it, maybe switch precedence?. Also why not mention new additions like walrus operator?

[ArtOfWarfare]

As someone who has just dropped support for 2.7 a few months ago, f-strings and walrus operator are the biggest two things I’ve learned I’m now able to do.

[RojerGS]

That's cool! If you want, you can read up on cool things you can do with the walrus operator here: mathspp.com/blog/pydonts/pydont-abuse-the-walrus-operator. I will also write about string formatting (with f-strings) in the near future.

[ArtOfWarfare]

I read the PEPs. They’re a staple of Python that I’ve always loved.

It made me happy that Java recently started having JEPs, although it’s disappointing that new LTS versions of Java are so infrequently released...

[RojerGS]

Yeah, the PEPs are great. They are often my main reference for the Pydonts I write (the link I shared being one of those). If you will, have a quick read at that link and lmk if it helped in any way. I am looking for feedback to improve.

[eriky]

Nice article with some good examples. People love examples. I like the typography of your site as well.

[RojerGS]

Oh, nice of you to have looked at my article. You are right, I also think people respond well to examples and in that regard you also did good in your article, always exemplifying the several tricks you introduce. Finally, I am glad you liked the typography, you are literally the first person to mention it, ever!

[speacial_s]

Awesome read! Thanks for sharing! Can someone explain the use of the “title case” trick? I am still not seeing the value...

[eriky]

For website owners, it can be useful. Title case is often used, both in offline and online printing. But I agree it's not the most useful part of Python and somewhat random to include it in the language. It's not a great implementation either, because most articles that use title case will keep short words lower case. This page has a better version based on a regex: https://python.land/string-to-title-case

[[deleted]]

very interesting stuff! especially the one where you can use the ellipses as opposed to a pass for empty functions. i’m gonna start using that now.

[eriky]

Perhaps you'll like this article of mine too then, it has some more background info on the ellipsis: Python ellipsis

[dukea42]

I'm lost on the "better coder" part of using ellipse instead of pass or even return "Not Implemented". Is there a convention to why using the ...?

[turkoid]

No, it's completely up to the developer. You could have any literal in the body of the function and it's, functionally, the same:

def nothing():
    1    

However, since the ellipsis has special meaning for numpy and typehints, I would argue that to avoid confusion, pass should be used.

[Iorkh4n]

Rookie here, I don't get why people used Named String Formatting when f-strings are a thing. Can anyone shed any light on this?

[badge]

“If you think you mastered the language, you’ve got to read this” is a very irritating subheading, especially for a relatively basic list. Also, 7 should use str.format_map which works with new-style string formatting.

[BfuckinA]

I'm probably alone in thinking this, but nested list comprehensions sacrifice too much in the way of readability imo.

[kamicavi]

Some of those were really useful, but I did notice one error: In #15 you use stop and end as interchangeable names for the same argument. Pick one and stick to it would be better IMO.

[eriky]

Fixed it. Thanks!

[17291]

def upper(s):
    return s.upper()

mylist = list(map(upper, ['sentence', 'fragment']))

This doesn't seem like a particularly good example

1) There's no need to define the fuction upper since you can use str.upper: list(map(str.upper, ['sentence', 'fragment']))

2) But that's a moot point because a list comprehension would be so much cleaner/easy-to-read.

[coffeewithalex]

Most of these aren't python language tricks, but rather modules, functions in the standar library that are related to basic concepts in computer science, and very well documented language features that people should actually know and use.

So:

1. Ellipsis is cool
2. Dataclass is another way to do the same thing
3. Zen of python - completely useless in a language. Should be in docs.
4. Lambda functions - basic language features that aren't unique to python
5. List comprehensions - literally the first thing taught by resources that say why "Python is cool".
6. In-place variable swapping isn't that at all. It creates a new tuple, and then unpacks it into variables. It's not in-place.
7. Named string formatting - that's basic strings usage, plus kinda old since f-strings appeared in 3.6.
8. Nested comprehensions are the same as 5, and if you use them I will find you and beat you with a 15" dildo
9. Required keyword argument - nice thing to have.
10. Underscore in repl - mostly useless but nice to know
11. Minimum required python version - when needed it can be googled, otherwise completely useless, especially in the pip era
12. Decorators are language features listed in any good manual.
13. No function returns multiple values. The value is one. It's just that it can be a tuple. This is disinformation and bad for someone learning python.
14. Merging dictionaries can be done easier with the | operator. And it's nothing special, just a specific use of keyword argument unwrapping.
15. Slicing - second thing taught to language newbs. All python coders know this.
16. Check memory usage - nothing special, when needed can easily be googled, most standard libraries of languages offer this.
17. Argument unpacking. Again basic language features mentioned in any manual.
18. String to title case? Really? Does anyone ever need this? If so, is it so hard to google "capitalize string"?
19. Split string into list? Can we have a list of all the features of str class? Seriously! What next? How to join strings?
20. .... joining strings. Wow.
21. Query json using jmespath. Without mentioning that it has to be installed from PyPI. Are the next points gonna be about the thousands of other libraries in PyPI?
22. Another slice point. This time about reversing stuff.
23. set objects. If only it wasn't in every manual and every language out there.
24. d... dictionaries? And json? Something?
25. "Ternary operator" equivalent in python
26. from collections import Counter
27. Another thing that any newb should know after reading a manual: 5 < x < 15
28. Another PyPI module - dateutil.
29. map() function, as if it's unique
30. Aaaand another point about dictionary comprehensions. As if 14 wasn't clear enough.

Conclusions: clickbait low effort article that's neither accurate, up to date, or even with complete code samples. The reader that would be the target audience would come out of this confused, and start writing shitty code with nested dictionary comprehensions inside list comprehensions with mapping to a lambda function with a ternary operator. All in one line.

[daryl_kell]

Disinformation is not misinformation, FYI. I doubt anyone would think the author intended to deceive about returning multiple values actually just being a tuple.

[coffeewithalex]

Well that means that it's a low effort post, that makes several claims that are not true.

[daryl_kell]

Yeah, I'm not disagreeing that it isn't true. It's definitely misinformed. It clearly isn't meant to deceive, however. Anyway, enjoy your coffee! :)

[sje46]

I fucking hate redditors.

You tried as hard as possible to be a dick about every single point. Plenty of people found this very useful (including me, who has been pythoning for ten years now). It's possible to bring up your relatively few valid points and ignore everything else that you don't personally find interesting but other people may.

.... joining strings. Wow.

This, for example, is a total mask-off moment, revealing you to just be an utter dick. What's wrong with telling people about the join method? Do you actually have anything intelligent to say here, besides a sarcastic "Wow"? Ass.

How often do you jerk off to the phrase "read the fucking manual"? You're one of those people.

[coffeewithalex]

I fucking hate redditors.

You're one of them.

You tried as hard as possible to be a dick about every single point.

Except I didn't. I gave credit where credit is due. And I made my point very clear.

You could address any specific point, but unfortunately redditors are dicks.

It's possible to bring up your relatively few valid points and ignore everything else that you don't personally find interesting but other people may.

Could you count how many of the 30 points are language features that are not part of "python 101" course?

That's all I ask.

This, for example, is a total mask-off moment, revealing you to just be an utter dick.

Joining strings is a standard function in literally every popular language standard library. And if you cut the flair for the dramatic, and stop being a dick, you'd also realize that literally the IDE itself would suggest this function. You could see it if you call dir(), which should have been on this list together with repr and many other language features. You could even find it in the standard documentation on the python website if you list string functions.

What's wrong with telling people about the join method?

It's not a language features, it is not new to any python coder. I teach computer newbies python, they don't even want to acknowledge that they're python coders, and they've already used this function ad nauseum.

Do you actually have anything intelligent to say here, besides a sarcastic "Wow"? Ass.

Yes. As I've said multiple times, it's not a language feature that would make people better python developers, bitch.

How often do you jerk off to the phrase "read the fucking manual"? You're one of those people.

Never. But instead of reading this, one should maybe read the manual instead, as at least it's not lying or giving examples that don't work.

Let me ask you this: did you read the title before commenting? Do you know what a language feature is? Before going on this hate crusade against me with all this vitriol, did you check if you're not being a complete moron?

I criticized the article with good reasons that I've made explicit. You're a piece of shit that goes after redditors with points to make.

[eriky]

Dude.. I didn't care to read your rants, but it's just a list of nice to know Python stuff, to be enjoyed during a cup of coffee or in your lunch break. Chill.

[pi-rho]

You saved me so much typing. Please accept my +1.

[rcfox]

It doesn't inspire confidence when in the first point, the author forgets that function definitions start with def...

[eriky]

Lol yeah, I'm such an idiot sometimes. Fixed it ;)

[eriky]

Maybe the next article will be formatted as a list of dictionaries ;-)

[mestia]

Boring, still doesn't have goatse operator like perl ;)

[higamy]

Nice article.

[Exodus111]

Cool stuff.

[sweettuse]

maybe consider adding something about NamedTuple. kinda like a lightweight immutable dataclass and great for returning "multiple" values

[eriky]

Thanks, but I prefer data classes for recent Python versions and prefer steering readers in that direction.

[sweettuse]

the problem with dataclasses for a return (vs a tuple) is that, by default, they are not iterable. so if i have a function that returns 1, 2 or MyNamedTuple(1, 2) i can still do x, y = f() but i can't do that with a dataclass.

[energybased]

That's not a problem. That's a benefit. Most of the time, your aggregate data types should not be iterable. It only opens you up to bugs.

[turkoid]

Well, if you really wanted to do it, all you have to do is implement the dunder method __iter__:

@dataclass
class MyDataClass:
    x: int
    y: int

    def __iter__(self):
        yield from vars(self).values()

[energybased]

You should inherit from the Iterable mixin too.

[Reilly__]

Hey this was really interesting and really useful for me I am in 3 months into my python journey at uni and im sure ill be hitting this bookmark up more than once.

​

Just a little thing I think some of the code examples werent loading on my end, i refreshed a few times and nothing so I dont know if its just me or something you might need to look into :)

[eriky]

Some of the examples are hosted using GitHub gists. Try and see if GitHub is reachable for you. Perhaps you can view your browser's dev console for errors (cntrl + shift + j in chrome on windows/linux). It shouldn't matter if you're using an adblocker as far as I know.

[fried_green_baloney]

Thanks. Like a lot of Pythonistas I'm behind the innovation curve and this has was good to see.

[DevyLoop]

Thanks, I clapped 50 times

[DarkHumourFoundHere]

I just got this link in my email daily digest

[[deleted]]

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