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Python Mutability (programming.dev)
submitted 1 year ago by to c/python@programming.dev
19 comments fedilink hide all child comments
 

See the Solution and Explanation.

all 19 comments

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[–] 6 points 1 year ago (3 children)

There's also a gotcha with default parameters:

def fun(a = []):
    a += [1]
    return a

fun()
print(fun()) # [1, 1]

issues I had with the tool you linkedI tried to make a link to this code in this visual debugger, but a link is made broken and can't be used without urlencoding spaces (I guess). Also the tool doesn't produce visual output in DuckDuckGo browser on Android

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  • [–] [S] 2 points 1 year ago (2 children)

    You can just write your code and then press "Get URL" to get the link: https://memory-graph.com/#code=def+fun%28a+%3D+%5B%5D%29%3A%0A++++a+%2B%3D+%5B1%5D%0A++++return+a%0A%0Afun%28%29%0Aprint%28fun%28%29%29+%23+%5B1%2C+1%5D

    DuckDuckGo problem, thanks for reporting.

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  • [–] 2 points 1 year ago (1 child)

    Yeah, I wrote code and pressed get URL, but then I copied what was shown in the window

    The clipboard content:

    https://memory-graph.com/#code=+%23+What+is%2Bthe+output+of+this+Python+program%3F%0A+++%0Adef+fun%28a+%3D+%5B%5D%29%3A+%0A++++a+%2B%3D+%5B1%5D%0A++++return+a%0Afun%28%29+print%28fun%28%29%29

    The window text:

    The following URL has been copied to your clipboard with:

    The current code
    Set breakpoints
    Playback timestep
    Play/Pause state

https://memory-graph.com/#code=+%23+What+is+the+output+of+this+Python+program? +++ def+fun(a+=+[]):+ ++++a++=+[1] ++++return+a fun()+print(fun())

    The latter doesn't work, and I didn't think of checking the former

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    • [–] 5 points 1 year ago (1 child)

    Wow, nice project!β€― I'm a 'visual person', I understand better when I see what's happening.

    That can help me a lot! :)

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    • [–] 2 points 1 year ago (6 children)

    As I would expect. Does the result surprise people?

    If so, rename the arguments to fun() to be r, s, t, and u. Just inside the function. Does the obvious two scopes now make it clearer?

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  • [–] 7 points 1 year ago (2 children)

    The fact that x += y modifies lists in place might be surprising if you're expecting it to be exactly equivalent to x = x + y.

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  • [–] 2 points 1 year ago

    To be fair, I had to read the linked question on SO to understand what was the possible alternative. I do expect that if I use += it is in place.

    On the other hand with Python and Java I always keep forgetting if everything is by value or by reference, I really miss some extra clarity of the languages where you can see if something is mutable when passed to a function

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  • [–] 3 points 1 year ago (2 children)

    Looks like this whole post is an ad for someone's project. The links hardly have to do with the post.

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    • [–] 1 point 1 year ago (5 children)

    Here is the link to the code which is being in-browser remote executed

    exercise14.py

    There is no "explanation" next to or within the file. A exercise14.rst or test_exercise14.py would be nice.

    The Explanation link provided contains a mountain of visual shit (aka noise) none of which looks like exercise14.py code.

    The OP is trying to teach us, i get that. Looks like i'm failing the (mountain of visual shit) reading comprehension section of this exercise.

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  • [–] [S] 2 points 1 year ago* (last edited 1 year ago) (4 children)

    Thanks for your feedback, much appriciated.

    I agree that an exercise14.rst would be nice, but to save time I've let the code speak for itself now together with the visualizaion. I'll probably revisit and better document the exercises later.

    At the Explanation link I try to give a general explanation about Pyrhon mutability (and copy later on), I agree some readers might find it hard to relate that to a specific exercise, but I don't want to write a specific explanation for each exercise.

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  • [–] 1 point 1 year ago (3 children)

    First i love the visualizations. It grew on me. And supportive of coding challenges posts. As long as there isn't a flood of them. Which there isn't.

    I get your position. That there just isn't an explanation for each and every exercise. The other comments made it seemed like there was.

    When i clicked on the Explanation link, the browser didn't initially scroll to the Mutability section. Went downhill from there.

    btw i'm too dumb to know the answer and too lazy to copy+paste the code into a REPR.

    All the other commenters are just dishonest pretending they totally got it without running the code ;-)

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  • [–] [S] 2 points 1 year ago* (2 children)

    Actually running the code? I got to the stage where only AI can help me understand anything ;-)

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  • [–] 1 point 1 year ago

    Ah! Haven't yet reached stubborn old geezer stage.

    Don't immediately understand exactly what the code does? Must be cuz of mental slippage. Like brain plague or residual PHP or jinja2 knowhow that can't be purged.

    We all know it's not from drug use or excessive party lifestyle. Maybe excessive retro Linux gaming?

    Whatever it is, those exercises are great diagnosis tool.

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  • [–] 1 point 1 year ago

    AI reads github issues and crapoverflow for us cuz that is where packages are mainly documented.

    The package documentation is a historical document according to every PEP ever. ;-)

    What if github issues&discussions disappeared tomorrow? That feeling in your ballsack is what free falling feels like?

    Forever wars? np we are due for some excitement.

    github disappearing suddenly ... that keeps me awake at night

    Is Copilot unemployment in it's future?

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