Knowing this can save you HOURS of debugging! (5 Python Pitfalls)

Being aware of these 5 Python Pitfalls can save you hours of debugging effort.
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[@johnjoyce]

The single element tuple gotcha is half the reason I always always add the comma after the last element of every collection. It always expresses correctly and if aligned with each collection member or element on separate lines, then it is easier to reorder the collection in code and see deltas in diffs and help git better understand merges as it is so line oriented.

[@__________________________6910]

Thanks, "Happy Teachers Day" from INDIA

[@b07x]

You're the same person who said that Loi should be the next James Bond.

[@__________________________6910]

​@@b07xyou remembered me

[@__________________________6910]

@@b07x YES

[@coniferviveur3788]

Thanks for that. Your explanations are very clear and your use of examples is excellent.

[@imdadood5705]

Once you learn the basics of python. This solidified the understanding further. Thank you for this!

[@johnjoyce]

Finally, most of these can be avoided by adopting the emerging more explicitly typed coding style using the typing module extensively with mypy and using explicit constructors to avoid ambiguity even when it is visual ambiguity. The fast and loose nature of many scripting languages has begun to wear thin and we are seeing the emergence of explicit typing style as scalable and reducing a class of runtime errors by preventing them. TypeScript is an example of this along with Hack and others.

[@TylerThomas]

you're right but I don't want you to be.

[@13thk]

4:58 this tip applies to any built-in unnamed collection(list, tuple, str) For example (1,2,3) == ((1,2,3)) is true unless (1,2,3) == ((1,2,3),) which is false Or [2,3] == ([2,3]) which is true

[@caiyu538]

great lectures. Really tricky in python. Thank you so much.

[@raminmousivand4257]

Fantastic tutorials. Please keep going buddy 👌🙏

[@pacersgo]

It is a very good video. I have written at least three of those bugs, that did take me quite some time to figure out what happened..

[@patloeber]

Haha we’ve all been there 😄

[@JohnZakaria]

I have done all of these mistakes as I started doing python. Accuracy 100%

[@castlecodersltd]

Really helpful, thank you ☺

[@AR-fh2uh]

I was there today. Working on a client server model. It wouldn't work for love or money. Turns out, after a complete refactor the client and server were using a different message header length. I was setting specifically in thier init statements.

[@davidbeauchesne7399]

thanks! good tips for the new python user.

[@raiyan22]

learned sth new today !! Thanks

[@vivekan97]

Very informative 👍👍👍 Looking for more

[@patloeber]

Glad you like it

[@lawrencedoliveiro9104]

1:54 Note that implicit string-literal concatenation happens at compile time, not run-time. It’s a feature copied from C, also present in C++ but for some reason omitted in Java and PHP. I like it, and I make use of it frequently. It’s more convenient for breaking long strings across multiple lines than triple-quoted strings. I use it to write things like this:

[@lawrencedoliveiro9104]

sys.stdout.write \ ( " ♯ nr scanned: %d, nr hashed: %d, time taken = %ds " "♯ delete: %d, touch: %d, move: %d " "♯ unindexed: %d " %

[@lawrencedoliveiro9104]

( nr_scanned, nr_hashed, round(finish_time - start_time), to_delete, to_touch, to_move, nr_unindexed, ) )

[@personx9450]

Helpful 👏

[@vinicus508]

4:25 when you showed this i had to pause to try to understand what in the world is that. And I asked myseld “why tf is it like this?”. But actually this makes a lot of sense, and its super useful now that I think of it

[@victorpinasarnault9135]

Thanks a lot

[@rendomstranger8698]

I wish I had seen this video 2 weeks ago. I spent about an hour debugging a program because of the whole 1 item tuple situation. Took me a while to figure out that it was the tuple that was causing problems and even longer before I discovered that the function it was a part of was returning a string instead of a tuple. Thinking about it further, I should probably be checking for type instead of length in my program and just leave the string as a string.

[@urilou777]

or just use C instead cuz python is bad

[@rendomstranger8698]

@@urilou777 Nah. I'll stick with Python for now. I'm trying to get into professional programming so no point in switching languages in the middle of a project that I'm planning to put on my CV.

[@Tennisbull-match-statistics]

What other functions are in place operations?

[@Yotanido]

I knew about all of these and could correctly predict what each shown program was going to do. That said, append being an in-place operation and returning None has annoyed me a lot when I first started to use python. Coming from Haskell, mutating lists like that was just... weird. I still think it should return the list, even if it does change it in place, since it would allow you to chain calls.

[@chaddaifouche536]

Or at least it should return an error value or something that makes it clear your error was assigning the result of an in-place modification... Though your chain calls argument is good, as expected coming from Haskell where it's quite common to compose several functions.

[@vandelayindustries2971]

Chaining it would be useful for people like us who know the difference between in-place and copying, but for beginners it could be confusing. They'll see a list being returned and assume it's a copy and so they'll treat it as such, introducing bugs all over their code. By returning None for in-place stuff and returning a value when it's a copy, there's never any doubt (the same way list.sort() returns None, but sorted() returns a copy).

[@lawrencedoliveiro9104]

If you don’t want to mutate the list, use the functional construct. Python does not claim‡ to be a pure-functional language, but at least it gives you the choice of functional constructs. ‡Is there really such a thing as a “pure-functional” language? Or only languages that _claim_ to be pure-functional?

[@saurrav3801]

🔥🔥🔥🔥Great job bro

[@patloeber]

thanks!

[@saumodipdas3624]

Really good video. Though I used to get correctly 4 of these but never paid attention to the errors otherwise. So thanks for the info. Keep it up 😀😀😀

[@dominikwodarczyk6714]

Thanks

[@johnjoyce]

Yeah. That string concatenation “feature” is a misfeature in most contexts. Should be removed along with unparenthesized tuple because similarly hard to spot comma can cause syntactically valid but crazy bugs.

[@laugedyret]

I love it!

[@patloeber]

Happy to hear that :)

[@akshaysrivathsa227]

Can u pls make a pytorch project like the snake game

[@patloeber]

thanks for the suggestion. which project would you like to see?

[@akshaysrivathsa227]

@@patloeber Pls make a general video so that we can implement it on any game we want.

[@majkelpl8611]

I preferred your face rather than memes. Video as always, great.

[@patloeber]

thanks for the feedback :)

[@JOHNSMITH-ve3rq]

Appalled at this language. Though I also love it 😂

[@maman14141414]

for the tuple example there is actualy a trick you can just write ("one",) wth a trailing comma to have the desired behavior

[@patloeber]

yep great tip!

[@MrCmon113]

I wrote a conditional that always returns true in my bachelor thesis. Hundreds of hours of GPU time wasted, because I only found the mistake after weeks.

[@patloeber]

oh noooo :D now this will never happen to you again

[@siranjeevis1176]

Post video more videos like this

[@patloeber]

I try :)

[@evlezzz]

Explanation for conditional expression is wrong. It has nothing to do with consistency. It's caused by operations priority within expression. Since priority for comma operator is lower than for conditional operator, "(a, b) if x else c, d" is actually parsed as "((a, b) if x else c), d".

[@lawrencedoliveiro9104]

The Python conditional-expression construct is a total abortion.

[@evlezzz]

@@lawrencedoliveiro9104 It's not, if used properly.

[@nort1793]

I am sixth!!!

[@Jxrdy]

wtf python

[@JOHNSMITH-ve3rq]

My gosh that is such stupid behaviour by python. Ridiculous!!!

[@chaosopher23]

Those are not bugs, they are features.

[@hossumquat]

It's only a feature if the code does what you want it to. If it doesn't, it's a bug. So context matters for making the distinction.

[@chaosopher23]

@@hossumquat What would you call it if you put it in & didn't tell anyone but your dev team, just, let them find it? For example, a room or two in a video game where executable code could be run on purpose. Not like that log4j hot mess!

[@jesusmtz29]

i wonder who thought this was a good idea lol maybe ther'es a good reason

[@paulabraham2550]

Good grief. The more I learn about python ...

[@ktrivikram1311]

Your project name is wtf python 🤣

[@viddeshk8020]

😂 seeing this in 2023 😅

[@boem231]

This is exactly why I hate python

[@michalbotor]

i have never expected to burst into laughter once someone had explained to me where the flaw in the code lies... i'm talking about you: `x, y = (1, 0) if condition else None, None`

[@patloeber]

Haha glad I could entertain you