Comments by "Lawrence D’Oliveiro" (@lawrencedoliveiro9104) on "ArjanCodes" channel.

  1. 15:13 You could leave out both the “await” and the “async”. So “send‗async‗request” becomes a regular function which returns an awaitable.
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  2. ORMs don’t make any sense to me. The code doesn’t end up any simpler.
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  3. “Machine” does not have to mean “hardware”. For example, bytecode interpreters are commonly called “virtual machines” nowadays.
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  4. I started my career back in the early Apple Macintosh days. Back then, there was this document called the “User Interface Guidelines”, which carefully spelled out concepts like “interface stability” and “progressive disclosure” and feedback to confirm user actions. We were taught to care about actual user-interface testing, rather than just assuming that what we were doing would be “intuitive” to the user. But increasingly, I found that app vendors didn’t bother following these rules. And even Apple itself seemed to be moving away from them. Nowadays, it all seems to be about looks and following fashionable “design trends”. Hence the move away from the “3D” look to the “flat” look, which may be going back to “3D” now. Or what about this “dark theme” fad? What happened to usability testing? Seems nobody even bothers with that any more.
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  5. Another thing is, there are no language-independent ORMs. I do some stuff in PHP also, so I have to learn SQL anyway, I might as well do it properly.
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  6. 6:16 Just a note that splitting things out into separate files will slow down loading, compared to having it all in the same file.
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  7. An alternative way is to have the argument default to None. The function checks for this value, and replaces it with the current time (or other dynamically-computed value, as appropriate).
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  8. 12:35 But you could replace it with a docstring. Which could be dynamically generated, to incorporate the actual limit, and assigned to the ＿＿doc＿＿ property of the function object being returned.
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  9. 6:24 The argument is called “discount_perc”, but its interpretation is as a fraction, not as a percentage. I would say that is bad.
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  10. I think with nearly any GUI app, if it becomes really useful, then somebody will want to automate tasks with it. This is a good argument for separating the GUI frontend from the backend engine. So then you can invoke the backend via some kind of script or CLI, independent of the GUI. In fact, you could start your new app by writing it as CLI-only, and adding a GUI later.
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  11.  @ER-oj8mo  I have written seven-way joins in SQL. I don’t use triggers; all the business logic is in the application code, and anything repetitive can be put in a suitable function or class. That gives me much more power than SQL itself. Like being able to dynamically include/exclude fields/tables in a query.
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  12. Nothing specific to asyncio there.
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  13. 8:50 Properties are useful for wrapping getter/setter functions when you are creating a Python wrapper around an external C library using ctypes.
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  14. 2:04 I don’t have a problem with from-imports. If you search for “my_function”, eventually you will have to encounter either an actual definition or an import. That’s what your editor’s search function is for.
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  15. This is why we rely on the Olson zoneinfo database to manage all those headaches for us. Use standard library routines and let them worry about it.
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  16. If you have read/write properties on a class, specifying slots is a very good idea.
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  17. People seem to be very afraid of the various forms of injection attacks. In fact, they are quite easy to avoid.
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  18. 22:38 You shouldn’t have bothered with functools.partial. Just do with_default_logging = with_logging(logger)
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  19. 8:02 DBMSes themselves usually provide some kind of introspection facilities, though this varies a lot. For example, SQLite provides enough information that you should be able to programmatically derive the entire database schema without having to parse actual SQL, while MySQL/MariaDB is a bit more limited. The question is: do ORMs make use of this? Doesn’t seem like it.
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  20. I have used operator functions with functools.reduce(). Fun fact: reduce() was a built-in function in Python 2, demoted to being part of the functools module in Python 3.
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  21. 1:16 Unquoted brackets!
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  22. People think Emacs is old, but they forget that it was built by a whole bunch of smart hackers who lived and breathed coding, knew what they were doing, and were not beholden to marketing managers at any company. For example, they used an advanced programming language (LISP), which can still scare the pants off the Java/C♯/PHP crowd today. Does the automation language in your favourite editor understand closures and lexical binding? (Interestingly, the sort of concepts discussed in this very video.)
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  23. I would include an exception traceback as part of “some response our customer can send us”. Your subsystem writes logfiles, doesn’t it? Any exception crash should end up in there; tell them to send those.
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  24. 12:51 Yeah, but starting daylight saving is the easy transition to handle; what about ending daylight saving, when 3 a.m. occurs twice?
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  25. 7:38 As soon as you said it uses subclassing, I immediately thought “there must be a metaclass involved”. Had a look at the source code, and yes, that is how it works.
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  26. I notice you only talked about function decorators, not class decorators. They have their uses, too. I think the most extensive use I have made of custom decorators so far has been in my DBussy package, a pure-Python wrapper for libdbus. The information defining the D-Bus interface to a Python class is specified via a function decorator on each Python method implementing a D-Bus interface method, with a class decorator to tie it all together. Then when you register your class to receive messages, the dispatch mechanism knows how to decode incoming D-Bus method calls, convert the arguments and dispatch to the appropriate Python method. As a bonus, this same information is used to automatically generate the D-Bus XML introspection format, when another D-Bus peer sends you the introspection message. And conversely, when you introspect another D-Bus peer, this info is used to dynamically generate a “proxy interface class” -- a Python class whose methods simply send the appropriate D-Bus messages and return the responses.
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  27.  @kurt7020  Here’s a function which works in all cases: def sql_string_list(the_list) : "returns a list containing the quoted items of the_list, suitable" \ " for use in an “in” clause⋅" return \ "(" + ", "⋅join([sql_string(s) for s in the_list]) + ")" ♯end sql_string_list Another situation is: what about LIKE clauses?
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  28. A common use of a LIKE clause is to allow partial matches on user input, by bracketing it with “%” wildcard symbols. But consider, you want whatever the user types to be matched exactly, even if it happens to contain wildcard symbols.
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  29. 9:43 Still, it could be worse: it could be Java. I was doing some date/time conversions in an Android app some years ago, and it took me a while to realize that while every single method in a class might be deprecated, the class itself was still required elsewhere!
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  30. Perspective foreshortening, aka 1990s music video styleeee ...
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  31.  @christoferberruzchungata2722  It’s already a large chunk of the code in a single function. Splitting it off doesn’t seem very helpful, when the error message is already supposed to explain what the check is trying to achieve.
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  32. I don’t think there’s such a thing as “NoSQL” any more. Even the non-relational DBMSes are adopting forms of SQL for their query languages.
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  33. 12:50 I deal with that in one of two ways: * For some projects, there will be a schema file containing the requisite CREATE TABLE statements, included in the source tree and version-controlled along with everything else. * For other projects, particularly ones using SQLite, the program itself will automatically create the necessary tables each time it is asked to create a new database, so the CREATE TABLE statements will be in the program source code.
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  34.  @leftblank5315  Precisely. If you are after a “seamless” experience, then you have to avoid Windows.
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  35. I used islice() in a presentation I was giving on continued fractions. This was because I couldn’t be bothered putting a termination condition in the generator functions that were producing the coefficients, so islice() had the job of cutting an infinite series down to a finite length.
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  36. It can also help prevent typos.
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  37. Travelling faster than light inevitably leads to time travel.
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  38. It would be nice to make parts of the plumbing more declarative. For example, I share Arjan’s distaste for carrying around large amounts of XML. Why not define a Pythonic representation for that XML info? This is what I did in DBussy, my pure-Python wrapper for libdbus.
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  39. 4:07 Why not use the Decimal type?
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  40. Callable objects seem useful where you have a lot of state to hold. And perhaps you want to provide additional caller-visible methods to manage that state. Otherwise it would be simpler to use a closure.
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  41. You notice that Python effectively already has full generics, since function objects and class objects are constructed at runtime?
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  42.  @RitchieDiamond  Did you try assigning a suitably unique ＿name＿ to your lambda, to see if that helped with pickling? Presumably the problem is that pickling doesn’t actually include the code of the function, just some way to tie the recreation of the function object back to the original program code -- which almost certainly means the function name.
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  43. How about something as simple as mask = qah.ImageSurface.create \ ( format = CAIRO.FORMAT_A8, dimensions = resolution * raster_frac.denominator ) because I can never remember whether the format arg comes first, or the dimensions?
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  44. Just make sure your zoneinfo is up to date. Changes happen several times a year.
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  45. For long function/method calls, put the arguments one to a line, and give the whole expression a two-dimensional layout, e .g.:     aqsis_output = ReasonablePerms.subprocess.check_output \       (         args = ["aqsis"] + extra + [self._filename],         stdin = subprocess.DEVNULL,         stderr = subprocess.STDOUT,         universal_newlines = True,         cwd = self._parent._workdir,         timeout = self._parent.timeout       )
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  46. 4:50 Sounds like defining key fields in a database record.
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  47. 2:55 Have you looked at apsw? I prefer that to the standard Python sqlite module.
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  48. async-for needs the additional ‗‗aiter‗‗ mechanism in order to work, ‗‗await‗‗ on its own isn’t enough. I haven’t found async-for to be all that useful. So far, anyway.
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  49.  @ArjanCodes  That could be done if you could define your own custom operators, like “=>”.
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  50.  @Gnaritas42  Let’s compare actual code, then. Here’s the level-break example I posted in another comment: out․write("<TABLE>\n") out․write("<TR><TH>Planet<∕TH><TH>Moon<∕TH><∕TR>\n") items_iter = db_iter \ ( db, "select planets․name, moons․name" " from planets left join moons on planets․id = moons․parent" " order by planets․name, moons․name" ) cur_planet = None while True ∶ item = next(items_iter, None) if item == None or cur_planet != None and item[0] != cur_planet ∶ if cur_planet != None ∶ out․write \ ( "<TR><TD><I>Count∶<∕I><∕TD><TD>%d<∕TD><∕TR>\n" % count ) cur_planet = None ♯end if if item == None ∶ break ♯end if out․write("<TR><TD>") if cur_planet == None ∶ ♯ first moon for next planet cur_planet = item[0] count = 0 out․write("<B>" + html․escape(item[0]) + "<∕B>") else ∶ ♯ second or subsequent moon, don’t repeat planet name out․write(" ") ♯end if out․write("<∕TD><TD>") if item[1] != None ∶ ♯ there is a moon out․write(html․escape(item[1])) count += 1 else ∶ ♯ that’s no moon out․write("<I>(none)<∕I>") ♯end if out․write("<∕TD><∕TR>\n") ♯end while out․write("<∕TABLE>\n") Show us how an ORM will make that simpler.
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