python - tail stuck under the rocks?

Lost User

OriginalGriff wrote:

"no need to declare variables" sends a shiver down my spine.

Er, isn't that exactly why the "var" keyword was invented? A few years from now no one will be using proper typed variables any more.

OriginalGriff

Oh, no, no, no, no! Python's version is worse: you don't need to declare the variable using "var", or "Dim", or anything - just pick a name and assign a value. So if you misspell it ... that's a new variable. Just like FORTRAN was back in the day (1977). And that caused a probe to miss the planet Venus completely, so what it does in a banking app, or a Boeing 737 Max is not something you want to think about too hard, really. Strongly typed variables should be mandatory in all languages used in the 21st century!

Sent from my Amstrad PC 1640 Never throw anything away, Griff Bad command or file name. Bad, bad command! Sit! Stay! Staaaay... AntiTwitter: @DalekDave is now a follower!

Lost User

OriginalGriff wrote:

Python's version is worse

I agree, but you can still do quite a bit of damage with var.

OriginalGriff wrote:

Strongly typed variables should be mandatory in all languages used in the 21st century!

That is definitely true; but will teachers explain that properly to their students?

r_hyde

But a `var` (as in C#, say) isn't at all the same thing as an untyped (or rather, dynamically-typed) variable (as in Python). When you write `var x = 5;`, `x` is still an `int` just the same as if you'd written `int x = 5;`, you're just helping yourself save some keystrokes and letting the compiler infer the type (ok, you're not saving any keystrokes in that example, but not every type name is as succinct as `int` ;P ). You can't then turn around and write `x = "snuggles";` or the compiler will throw a fit, unlike Python where it would be perfectly legal. More and more people might be using `var`, but let's not confuse that with "no one will be using proper typed variables any more!"

Lost User

OriginalGriff wrote:

just pick a name and assign a value. So if you misspell it ... that's a new variable

but how do you misspell "i"

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OriginalGriff

'j'? 'u', 'o', 'k'? All easy to do, especially on a "soft keyboard". :laugh:

Sent from my Amstrad PC 1640 Never throw anything away, Griff Bad command or file name. Bad, bad command! Sit! Stay! Staaaay... AntiTwitter: @DalekDave is now a follower!

David ONeil

Use Cryllic. Word doesn't match the second as 'sit': sit sіt

The forgotten roots of science | C++ Programming | DWinLib

OriginalGriff

There is also the "Extra quote character": ''' which looks just like the ones around it, but will not compile in other peoples code - not that you would replace any, I'm sure ... :laugh:

Sent from my Amstrad PC 1640 Never throw anything away, Griff Bad command or file name. Bad, bad command! Sit! Stay! Staaaay... AntiTwitter: @DalekDave is now a follower!

Sander Rossel

Richard MacCutchan wrote:

I agree, but you can still do quite a bit of damage with var.

In what language? JavaScript? Certainly, but JavaScript doesn't really get much better than that... In C# it's still a typed variable, so it's exactly the same thing as explicitly using the type name except instead of the type name you use var. So no damage there, except to readability.

Best, Sander sanderrossel.com Continuous Integration, Delivery, and Deployment arrgh.js - Bringing LINQ to JavaScript Object-Oriented Programming in C# Succinctly

Sander Rossel

Dictionary<string, IEnumerable<IEnumerable<SomeValue>>> valuesPerLineFromACsvFileByKey = new Dictionary<string, IEnumerable<IEnumerable<SomeValue>>>();

or:

var valuesPerLineFromACsvFileByKey = new Dictionary<string, IEnumerable<IEnumerable<SomeValue>>>();

:D

Best, Sander sanderrossel.com Continuous Integration, Delivery, and Deployment arrgh.js - Bringing LINQ to JavaScript Object-Oriented Programming in C# Succinctly

Sander Rossel

I know Haskell has it too. I know, because I had a school assignment that I've been looking at for two hours because I mixed up a few spaces with a tab... X|

if x is a:
do //...

Isn't the same as:

if x is a:
do //...

:rolleyes: It does produce some really clean and concise code though!

Best, Sander sanderrossel.com Continuous Integration, Delivery, and Deployment arrgh.js - Bringing LINQ to JavaScript Object-Oriented Programming in C# Succinctly

David ONeil

OriginalGriff wrote:

- not that you would replace any, I'm sure

If I wasn't using a strongly-typed language, and had an asshole for a coworker that needed a lesson, I certainly would! Send him a copy in which a variable has unicode changes but looks the same: "It works for me, I can't understand why you are having problems!" :rolleyes: :rolleyes: :rolleyes:

The forgotten roots of science | C++ Programming | DWinLib

GuyThiebaut

I started looking at Python in my home hobby time around 6 months ago and while it is a bit strange at first, I now find the indentation makes the code easier to read without brackets. I know IDEs allow you to indent bracketed languages but I find that Python easier to read. If you find the indentation strange, wait until you get on to the coding standards where lines should not exceed 79 characters in length.

“That which can be asserted without evidence, can be dismissed without evidence.”

― Christopher Hitchens

GuyThiebaut

Which is why I see Python as a poor choice for teaching beginners to 'code'. Take this class definition containing a function:

class StringFormat(object):

@staticmethod
def FloatToStringFormat(num: float, decimalPlaces: int) -> str:
    return "{:.{}f}".format(num, decimalPlaces)

Calling it like this:

resultAsString = StringFormat.FloatToStringFormat(20.123, "2")

I would expect to get an error as I am passing in a string rather than an integer for decimalPlaces. But no, Python happily sets resultAsString to "20.12"

“That which can be asserted without evidence, can be dismissed without evidence.”

― Christopher Hitchens

Mike Winiberg

It's interesting to see in this discussion that one of python's more attractive features is seen as a disadvantage 8) Once again, the debate here about whether the language is 'good' or not seems to have nothing to do with whether it actually is good or otherwise, but simply amounts to 'does it fit my idea of how a language should work'. If I've learnt anything from over 40 years of software development, it is that (with a few domain specific exceptions) the skill of writing good software - don't mistake me here, I'm not saying that I write good software! - has almost nothing to do with the language you write it in, and everything to do with domain knowledge and the skill of the programmer(s). Every language has rules; every language has flaws. Being aware of both and using/avoiding them so you produce good code is what it's all about. The behaviour cited above as being 'problematic' is exactly why I use Python for certain types of project. 8)

GuyThiebaut

Mike Winiberg wrote:

has almost nothing to do with the language you write it in, and everything to do with domain knowledge and the skill of the programmer(s).

I agree. I am glad you used the word "almost", because using Windows batch scripting for some devops work I have been doing has resulted in me having to work around the language and do things in a manner that I would not see as particularly elegant. Of course I could rewrite it with powershell scripting, which is on my list, but when you are working on systems that are business critical - doing a large code refactor is not always possible largely due to the cost to the business.

“That which can be asserted without evidence, can be dismissed without evidence.”

― Christopher Hitchens

Mike Winiberg

Oh yes, I was careful to say "almost"! 8) It never ceases to amaze me how complex a process could be constructed with DOS batch scripts - often by relying on obscure side-effects of small .COM files etc. I've always liked Powershell (although I rarely use it!) because it seemed a genuine attempt to provide a full batch environment for windows with 'proper' controlled access to the entire system. I do find the verbosity of the naming convention somewhat off-putting though (as indeed is the case for some other languages) - ridiculously long and complex variable names can be as difficult to manage as i, ii, iii and iiii etc! (I once spent over a day hunting down a bug in some C++ code where a stupidly long descriptive variable name had been used in multiple places with two different internal spellings via a macro such that the compiler didn't 'notice' the variants!)

Fueled By Decaff

C#

var elapsedTime = stopwatch.ElapsedMilliseconds;
var processedCount = GetProcessedCount();
var processedPerSecond = processedCount / elapsedTime * 1000;

Spot the bug.

Sander Rossel

Fueled By Caffeine wrote:

var processedPerSecond = processedCount / elapsedTime * 1000;

Probably there, you get an int instead of a decimal? However, changing var to decimal will still result in a wrong output as an int is silently cast to a decimal, but that doesn't change outcome of the divide operation. The fix I think you're looking for is:

var processedPerSecond = (decimal)processedCount / elapsedTime * 1000;

Now here is a fun bug, which I've seen go wrong multiple times...

var query = databaseContext.SomeTable;
query = query.Where(x => x.SomeBoolLimitingTheResultFromThousandsToTens);
return query.ToList();

In this piece of code the query variable is of type IQueryable. That means the Where that is executed is actually Queryable.Where(IQueryable, Expression). The actual database call, with WHERE clause, is executed on the ToList method (or more precise, in the Enumerator). Now someone comes and changes the code, the first line becomes var query = databaseContext.SomeTable.ToList(); Suddenly, the type of query has changed to IEnumerable! The database query WITHOUT the WHERE clause is executed and Enumerable.Where(IEnumerable, Func) is executed to filter the collection in-memory. You now get thousands of records instead of tens, while the in-memory Where is probably more expensive than the database WHERE. All in all a nice performance hit... That is actually the only bug I've ever encountered while working with var, and it's pretty specific. And the only reason it goes wrong is because IQueryable and IEnumerable have pretty much the same extension methods, save for Expression and Func, but a Func can be implicitly cast to an Expression. Fun times :)

Best, Sander sanderrossel.com Continuous Integration, Delivery, and Deployment arrgh.js - Bringing LINQ to JavaScript

kalberts

lopatir wrote:

but how do you misspell "i"

Right. That cost me a couple days of work, in the days when Fortran, as well as hardcopy code, were still around. (Yes I know there are languages called Fortran today, but they look completely different!). The loop went trhough once (as Fortran always does), but wouldn't repeat. I didn't discover the problem until I sat down with a printout of the disassebled binary code. Fortunately, the disassembler made use of the symbol defintions in the debug info, and fortunately, the printer (as opposed to the screen) used serif fonts. Then I could distinguish an "l" from an "I", so a conditional jump out of the loop used a diferent variable from the intended one. There are several such "false friends". I should have known, because in my student days, one of my friends who was a TA in the elementary Fortran programming class caused and "incident": The professor insisted on Norwegian variable names, so instead of "QUEUE" the variable should be named "KØ". "Ø" isn't recognized in Fortran, but ø is commonly transcribed to English as oe, which makes it "K0E". Because we have Ø as a letter, we do not slash zeroes here. Depending on the typeface, KOE and K0E may look almost perfectly identical. They did on our screens. When Jon discovered, he exclaimed loudly so that everybody around could hear hear it to the very good-looking, 18 year old female freshman: "Look, here you are not saying k-oh-e, you are saying k-null-e!" Zero is "null" in Norwegian and "knulle" means f**k... Jon didn't realize was he was "suggesting" until the word had been pronounced, and he got so ashamed that he wanted to flee away. But the girl did accept his excuses. Actually, it doesn't take national characters, like ø, to confuse 0 and O - even in English-speaking environments, non-slashed zeroes are common. Some typeface do not distinguish much between 1 and l either - I have seen troubles caused by that pair as well.