On Jan 15, 9:00 pm, Bruno Desthuilliers <bruno. [EMAIL PROTECTED]> wrote: > Lie a écrit : > > > > > On Jan 7, 2:46 am, Bruno Desthuilliers > > <[EMAIL PROTECTED]> wrote: > >> Lie a écrit : > > >>> On Jan 5, 5:40 pm, [EMAIL PROTECTED] wrote: > >>>> Jeroen Ruigrok van der Werven wrote: > >>>>> Shouldn't this be: > >>>>> self.startLoc = start > >>>>> self.stopLoc = stop > >>>> Thanks! Of course it should. Old Java habits die slowly. > >>> No, seriously it isn't Java habits only, most other languages wouldn't > >>> need explicit calling of class name. > >> Where is the "explicit calling of class name" exactly ? > > > Perhaps I was a bit tired when writing that (I wouldn't understand > > what I wrote if I were you)... what I meant is most other languages > > doesn't usually enforce us to explicitly state the containing class > > name, which in python is generally called "self". > > 'self' (or whatever you name it) is not the "containing class name",
Current instance is what I meant, thanks for pointing out the incorrect term I used. > it's the first argument of the function - which usually happens to be > the current instance when the function is used as a method. And that's the point, self (or anything you name it) is almost always the current instance and that makes it functionally the same as Me and this in VB and Java. > > Most other languages > > 1) automatically assign the containing class' object > > s/containing class' object/current instance/ > > > in a keyword > > (Java: this, VB: Me) behind the screen, > > That's not very far from what a Python method object does - > automatically assign the current instance to something. The difference > is that Python uses functions to implement methods (instead of having > two distinct contructs), so the only reliable way to "inject" the > reference to the current instance is to pass it as an argument to the > function (instead of making it pop from pure air). It isn't very far, but Python makes it obvious about the assignment (not behind the screen). > There are some benefits to this solution. One of them is the ability to > dynamically assign functions as methods. So if you do have some > function taking an object as first argument, you can easily turn it into > a method. Indeed, many languages doesn't allow dynamic assignment of function which makes having an automatic assignment of current instance to Me/ this possible and with minimal harm. > > and 2) automatically searches > > variable name in both the local variable table and the containing > > class variable table (so to refer to a class variable named var from a > > method inside the class, we only need to write var, not self.var as in > > python). > > This - as you know - cannot work well with Python's scoping rules and > dynamicity. Anyway, implicit object reference is definitively a > BadThing(tm) wrt/ readbility, specially with multiparadigm languages > (like Python or C++). Why do you think soooo many C++ shops impose the > m_something naming scheme ? Implicit object reference for the containing class has little harm, if a class is so complex that there are more than 10 class-level variable, then it is obvious that that class needs to be fragmented to smaller classes. Remembering less than 10 variable and avoiding naming collision among just 10 variable is not hard (and 10 is really too many, most classes should only use 2-4 variables), especially if you have a good IDE that employs Intellisense-like technology (IDLE has it). And it is always a Bad Thing(tm) to use the same name for two variable in the class and in function (which is the main and only source of possible ambiguity) in ANY language, even in Python. > Anyway, I actually know 3 languages (4 if C# works the same) that has > this implicit 'this' (or whatever the name) 'feature', and at least 5 > that don't. So I'm not sure that the "most other languages" qualifier > really applies to point 2 !-) What's this 5 languages? Are they a mainstream, high-level languages or lesser known, low-level languages? C-family, Java, and Basic are the Big Three of high-level programming language. > > In VB, Me is extremely rarely used, > > I used to systematically use it - like I've always systematically used > 'this' in C++ and Java. And that is what reduces readability. A proficient VB/C/Java programmer would frown upon the extra, unneeded garbage as they thought it was clear already that the variable refers to a class-level variable. It is a different story if, like Python, the use of self is enforced by the language, the self wouldn't be viewed as extra unnecessary garbage. > > in Python, self is all > > over the place. Well, there is positive and negative to both sides, > > convenience in VB, and flexibility in Python. > > As far as I'm concerned, there's *no* positive point in implicit object > reference, and there has never been (and before some paranoid nutcase > around accuse me of overzealous biggotry : I already held this very same > opinion years before I discovered Python). There is one major positive point: convenience and shorter code. (isn't that two?) As I've pointed out, there is little harm in class-level variable's implicit reference. > > Compare the following codes: > > VB.NET: > > Public Class A > > Dim var > > Public Function aFunction() > > return var > > Add three levels of inheritence and a couple globals and you'll find out > that readability count !-) It's the mental model that have to be adapted here, if the current class is inheriting from another class, you've got to think it as names from parent class as it is a native names, so you don't actually need to know where the variable comes from since knowing where it comes from is breaking the encapsulation (which, in Python is very weakly implemented, which favors flexibility in many cases[1]). [1] In Python, it is impossible to create a completely private variable, which is the reason why the mental model of these other languages doesn't fit Python. > In any non-trivial piece of C++ code, and unless the author either used > the explicit 'this' reference or the 'm_xxx' naming convention, you'll > have hard time figuring out where a given name comes from when browsing > a function's code. If you're used to the implicit naming scheme it's easy to know where a variable came from, if not the current scope, it's the class' scope and searching two short variable tables (SHORT! Creating complex classes is for stupid programmers[2]) at the same time isn't an expensive operation for human-being, especially if memoization is implemented. [2] I used to create an extremely complex classes when I was still green in programming, and that hits me back many times. Small, simple class is A Good Thing(tm). Class should use less than 10 variables, although the recommended number is 2-3 variables. Function names should be as little as possible, the use of overloading and overriding should be maximized. As a final note: I don't think implicit class reference is superior to explicit class reference, neither do I think explicit class reference is superior to implicit class reference. I think both have their own +s and -s. I only pointed out that implicit do have its benefits, depending on the language used (obviously Python wouldn't benefit from using implicit behavior, due to it being extremely dynamic). -- http://mail.python.org/mailman/listinfo/python-list