Re: What python can NOT do?
Boot loaders are another type of software which would be impractical to write in existing Python implementations. I wonder if TinyPy (http://www.tinypy.org/) could be used to write a boot loader. It would probably need some more code to replace the services it uses from an OS, and perhaps it would need to work in 16bit program mode on x86 - but maybe it's doable? tinypy is a minimalist implementation of python in 64k of code -- дамјан ( http://softver.org.mk/damjan/ ) Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it. - Brian W. Kernighan -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
In article 0022052b$0$2930$c3e8...@news.astraweb.com, Steven D'Aprano st...@remove-this-cybersource.com.au wrote: On Fri, 28 Aug 2009 15:37:46 -0700, qwe rty wrote: i know that an interpreted language like python Languages are neither interpreted nor compiled. *Implementations* are interpreted or compiled. SNIP Thanks for an excellent overview. There is this one point I don't understand: Existing Python implementations don't give you direct access to hardware, and bit-manipulation has a lot of overhead in Python. Numerical Surely you don't mean that 0x17 0xAD has more overhead than 17 + 123 So what do you mean here? SNIP -- Steven Groetjes Albert -- -- Albert van der Horst, UTRECHT,THE NETHERLANDS Economic growth -- being exponential -- ultimately falters. alb...@spearc.xs4all.nl =n http://home.hccnet.nl/a.w.m.van.der.horst -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Tue, 08 Sep 2009 00:09:26 +, Albert van der Horst wrote: Existing Python implementations don't give you direct access to hardware, and bit-manipulation has a lot of overhead in Python. Numerical Surely you don't mean that 0x17 0xAD has more overhead than 17 + 123 So what do you mean here? What I mean is that bit-manipulation in low-level languages like C is very close to the metal, and hence very efficient. In Python, *all* operations (including bit-manipulation and arithmetic) has the overhead of the Python virtual machine. You won't notice the difference if you're just ANDing a handful of numbers, but if you're doing millions of them (say, you're doing industrial-strength encryption) you certainly will. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Aug 28, 5:37 pm, qwe rty hkh00...@gmail.com wrote: i know that an interpreted language like python can't be used to make an operating system or system drivers. what else can NOT be done in python? what are the limitations of the language? Neither of those is strictly true. It is true, though, that Python cannot be used to write arbitrarily complex one-liners, though. -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Fri, 04 Sep 2009 08:21:15 -0700, Mike Coleman wrote:
It is true, though, that Python
cannot be used to write arbitrarily complex one-liners, though.
Incorrect.
exec x=1\0while x 5:\0 x+=1\0print x.replace('\0','\n')
5
Take (almost) any arbitrary piece of Python code. Replace all newlines by
nulls. Escape any quotation marks. Wrap the whole thing in quotes, and
pass it to exec as above, and you have an arbitrarily complex one-liner.
--
Steven
--
http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On 2009-09-05, Steven D'Aprano st...@remove-this-cybersource.com.au wrote:
On Fri, 04 Sep 2009 08:21:15 -0700, Mike Coleman wrote:
It is true, though, that Python
cannot be used to write arbitrarily complex one-liners, though.
Incorrect.
exec x=1\0while x 5:\0 x+=1\0print x.replace('\0','\n')
5
Take (almost) any arbitrary piece of Python code. Replace all newlines by
nulls. Escape any quotation marks. Wrap the whole thing in quotes, and
pass it to exec as above, and you have an arbitrarily complex one-liner.
I don't understand the reason for the newline/null swapping.
Why not just do this?
exec x=1\nwhile x 5:\n x+=1\nprint x\n
5
--
Grant
--
http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Fri, 04 Sep 2009 22:27:39 -0500, Grant Edwards wrote: Take (almost) any arbitrary piece of Python code. Replace all newlines by nulls. Escape any quotation marks. Wrap the whole thing in quotes, and pass it to exec as above, and you have an arbitrarily complex one-liner. I don't understand the reason for the newline/null swapping. Good point. I was just over-complicating it. Oops. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Non-deterministic computing (was: What python can NOT do?)
Steven D'Aprano st...@remove-this-cybersource.com.au writes: On Sat, 29 Aug 2009 05:37:34 +0200, Tomasz Rola wrote: My private list of things that when implemented in Python would be ugly to the point of calling it difficult: 1. AMB operator - my very favourite. In one sentence, either language allows one to do it easily or one would not want to do it (in an ugly way). http://www.randomhacks.net/articles/2005/10/11/amb-operator Fascinating, but I don't exactly see how that's actually *useful*. It strikes me of combining all the benefits of COME FROM with the potential performance of Bogosort, but maybe I'm being harsh. There's a chapter on this (non-deterministic computing in general, and `amb' in particular) in Abelson's Sussman's book, `Structure and Interpretation of Computer Programs': http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-28.html#%_sec_4.3 It's an interesting read (the chapter, as well as the rest of the book). On the other hand, it sounds rather like Prolog-like declarative programming. I fear that, like Prolog, it risks massive performance degradation if you don't apply the constraints in the right order. One of the classic arguments in the other direction is that imperative programming (as is common in Python ;)) risks massive *incorrect results* if you don't apply the side-effects in the right order :) -- Don't be afraid to ask (Lf.((Lx.xx) (Lr.f(rr. -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Sat, 29 Aug 2009 23:07:17 +, exarkun wrote: Personally, I consider Python to be a good language held back by too-close ties to a naive interpreter implementation and the lack of a formal standard for the language. Name one language under active development that has not been harmed by a formal standard. (I think C doesn't count -- there was relatively little development of C after the standards process started.) I think you must mean harmed by a formal standard more than it has been helped, since that's clearly the interesting thing. And it's a pretty difficult question to answer. How do you quantify the harm done to a language by a standarization process? How do you quantify the help? These are extremely difficult things to measure objectively. For a start, you have to decide how to weight the different groups of users. For an application which is designed for end users and will be in a permanent state of flux, dealing with revisions to the language or its standard libraries are likely to be a small part of the ongoing development effort. For libraries or middleware which need to maintain a stable interface, or for code which needs extensive testing, documentation, audits, etc, even a minor update can incur significant costs. Users in the latter group will prefer languages with a stable and rigorous specification, and will tend to view any flexibility granted to the language implementors as an inconvenience. -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
exar...@twistedmatrix.com wrote: On 10:23 pm, a...@pythoncraft.com wrote: In article 4a998465$0$1637$742ec...@news.sonic.net, John Nagle na...@animats.com wrote: Personally, I consider Python to be a good language held back by too-close ties to a naive interpreter implementation and the lack of a formal standard for the language. ... For my part, I will agree with John. I feel like Python's big shortcomings stem from the areas he mentioned. They're related to each other as well - the lack of a standard hampers the development of a less naive interpreter (either one based on CPython or another one). It doesn't completely prevent such development (obviously, as CPython continues to undergo development, and there are a number of alternate runtimes for Python-like languages), but there's clearly a cost associated with the fact that in order to do this development, a lot of time has to be spent figuring out what Python *is*. This is the kind of thing that a standard would help with. Right. Python is a moving target for developers of implementations other than CPython. IronPython's production version is at Python 2.5, with a beta at 2.6. Shed Skin is at 2.x and lacks the manpower to get to 3.x. Psyco I'm not sure about, but it's 2.x. PyPy is at Python 2.5, but PyPy is currently slower than CPython. A solid Python 3 standard would give everyone a target to shoot for that would be good for five years or so. John Nagle -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Saturday 29 August 2009 02:14:39 Tim Chase wrote: I've also been sorely disappointed by Python's ability to make a good chocolate cream silk pie. This is not pythons fault - it is yours, for failing to collaborate with a good hardware designer for the robotics. - Hendrik -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Aug 29, 4:26 am, qwe rty hkh00...@gmail.com wrote: On Aug 29, 3:14 am, Tim Chase python.l...@tim.thechases.com wrote: what else can NOT be done in python? what are the limitations of the language? I understand there's a little trouble getting Python to prove that P=NP You'll also find that it only comes close to solving the unrestricted three-body problem and the Traveling Salesman problem is still limited to fallible heuristics and searching the entire solution set in better than O(2**n) time. I forgot about solving the Spam problem entirely. And answering poorly worded/thought-out questions on the internet... I've also been sorely disappointed by Python's ability to make a good chocolate cream silk pie. -tkc if you don't know the answer please don't reply If you want to ask a silly question don't ask it. -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Sat, 29 Aug 2009, Timothy N. Tsvetkov wrote: On Aug 29, 4:26 am, qwe rty hkh00...@gmail.com wrote: On Aug 29, 3:14 am, Tim Chase python.l...@tim.thechases.com wrote: what else can NOT be done in python? what are the limitations of the language? [...] I forgot about solving the Spam problem entirely. And answering poorly worded/thought-out questions on the internet... I've also been sorely disappointed by Python's ability to make a good chocolate cream silk pie. -tkc if you don't know the answer please don't reply If you want to ask a silly question don't ask it. The question the OP asked was not silly. Regards, Tomasz Rola -- ** A C programmer asked whether computer had Buddha's nature. ** ** As the answer, master did rm -rif on the programmer's home** ** directory. And then the C programmer became enlightened... ** ** ** ** Tomasz Rola mailto:tomasz_r...@bigfoot.com **-- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Sat, 29 Aug 2009, Steven D'Aprano wrote: On Sat, 29 Aug 2009 05:37:34 +0200, Tomasz Rola wrote: My private list of things that when implemented in Python would be ugly to the point of calling it difficult: 1. AMB operator - my very favourite. In one sentence, either language allows one to do it easily or one would not want to do it (in an ugly way). http://www.randomhacks.net/articles/2005/10/11/amb-operator Fascinating, but I don't exactly see how that's actually *useful*. It strikes me of combining all the benefits of COME FROM with the potential performance of Bogosort, but maybe I'm being harsh. Usefullness is totally different thing, I agree. However, amb could still find some following. I guess it is more about personal taste and willingness to look for better idioms in programming. I can imagine when they introduced for and while loops, people were pointing at conditional goto as more practical (I think every control structure can be modeled with it). Id doesn't mean amb is better idiom, but it is something that could be tried - or not. One could write like this: (partially stolcopied from the above link) a = amb 1, 2, 3 b = amb 4, 5, 6 c = amb 7, 8, 9 if a*b + c != 27 : amb print a,b,c or one could write like this: for a in [1, 2, 3]: for b in [4, 5, 6]: for c in [7, 8, 9]: if a*b+c == 27 : print a,b,c break Which one would I choose? Well, amb of course. I consider it to be more readable which is, for me at least, useful. Now, try to imagine the same with ten variables. And longer lists. And some problems do not fit well into numpy (they could be non-numerical in nature). On the other hand, it sounds rather like Prolog-like declarative programming. I fear that, like Prolog, it risks massive performance degradation if you don't apply the constraints in the right order. Of course, but this can be optimised. Either by hand or by a good compiler (whatever this means). Performance degradation is connected with abuse of every other programming technique, too. And besides, I believe one would sometimes trade performance for the ability to clearly express the idea behind the algorithm. Just as is the case with choosing Python rather than Java. For things I use Python for, I wouldn't use Java or C. Even though C is one of my beloved languages. If I ever used Prolog for anything, I wouldn't like to rewrite it in C or Python. I mean, languages should (in theory) be chosen and used with some consideration. 2. Changing the language from the inside. Everybody can change the interpreter, right? But how about doing some bigger, maybe even fundamental change to the language by means offered by the language itself? Like Forth. You need it in Forth, because it has a very sparse set of language features, and everything is bootstrapped from a small set of commands, so the ability to re-define the language as you go is (1) necessary and (2) free. It also leads to writing code in an incredibly expressive manner. I've never done anything big in Forth. I only had a two weeks long exposure to it in times, when you loaded such things from casette recorder ;-/... But from time to time I find some interesting pieces, like a disk driver whose source would fit into a comment of one Python function :-). But for Python, I don't know... it sounds cool, but in practice? It sounds like the sort of thing that allows programmers to spend three hours writing a new control structure which will save them three minutes. It really is not so. Writing something for three hours and using it only once sounds more like programming excercise, less like real life work. To write a function I need to know at least two places in my code where it would be used (well, I am oversimplifying, ok? sometimes one place is sufficient). I think reasonable people would judge language extension by similar criteria. They would possibly stay away from this as long as possible (I have such possibility from some time but I just don't touch macros, which by my own words makes me reasonable, wow :-)... or a coward...). And of course, for all but the tiniest, one-man-band applications, readability is important. Sure, you've created a gee-whizz control structure which combines try, while and if into one keyword, and it automatically does logging and threading, fantastic. But how will anyone else be able to maintain it when you're gone? This is comparable to me creating a gee-whizz function library and using it. I cannot see a problem as long as I document (with use cases, tests etc). There is something better in this idea. Suppose I would have invented a better control structure and posted the source code here? Some would have found it amusing, others would have tried it, posted their comments, leading to improvements and further spreading. Finally - who knows - it could have found a way in to a standard. And
Re: What python can NOT do?
Theoretically a microkernel could be used to do the stuff python directly couldn't do and the rest could be done once an interpreter was loaded in theory. On Fri, Aug 28, 2009 at 4:37 PM, qwe rty hkh00...@gmail.com wrote: i know that an interpreted language like python can't be used to make an operating system or system drivers. what else can NOT be done in python? what are the limitations of the language? -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Aug 28, 7:05 pm, Tim Chase python.l...@tim.thechases.com wrote: qwe rty wrote: i know that an interpreted language like python can't be used to make an operating system or system drivers. As long as you are willing to write the OS hooks in C, you can write the userspace device drivers in Python: Writing your OS hooks in C isn't a problem because you could write a C compiler in Python ;-) -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Aug 28, 6:37 pm, qwe rty hkh00...@gmail.com wrote: i know that an interpreted language like python can't be used to make an operating system or system drivers. what else can NOT be done in python? what are the limitations of the language? Now that you have some good answers, may I ask what what your reason was for posting this question? -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
qwe rty wrote: On Aug 29, 5:11 am, Nobody nob...@nowhere.com wrote: On Fri, 28 Aug 2009 17:26:06 -0700, qwe rty wrote: if you don't know the answer please don't reply If you don't understand the question, don't post it in the first place. don't be so angry ,not good for your health You forgot your smiley emoticon! Since everyone else is posting in a light-hearted manner (not angry as you say), I choose to read your post in this light as well. What Nobody was really trying to say, is ask your question in a better way and you'll get a better answer. -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
exar...@twistedmatrix.com wrote: For my part, I will agree with John. I feel like Python's big shortcomings stem from the areas he mentioned. They're related to each other as well - the lack of a standard hampers the development of a less naive interpreter (either one based on CPython or another one). The reference manual is *intended* to define the 'standard' Python language. It doesn't completely prevent such development (obviously, as CPython continues to undergo development, and there are a number of alternate runtimes for Python-like languages), but there's clearly a cost associated with the fact that in order to do this development, a lot of time has to be spent figuring out what Python *is*. This is the kind of thing that a standard would help with. Such developers occasionally raise questions about ambiguities in the ref manual on the pydev list. This is part of the editing process. There is an effort underway to separate the CPython test suite into two parts: test of standard Python behavior, which all implementations should pass, and tests of the CPython implementation, which other implementations need not pass. It will move as fast as volunteer effort moves it. tjr -- http://mail.python.org/mailman/listinfo/python-list
What python can NOT do?
i know that an interpreted language like python can't be used to make an operating system or system drivers. what else can NOT be done in python? what are the limitations of the language? -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
qwe rty wrote: i know that an interpreted language like python can't be used to make an operating system or system drivers. what else can NOT be done in python? what are the limitations of the language? Python is a high level language. It's not designed for low level stuff like bit operations or direct hardware access. However it can be used as a glue language for low level code written in C or ASM. Christian -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Aug 28, 5:37 pm, qwe rty hkh00...@gmail.com wrote: what else can NOT be done in python? what are the limitations of the language? Why would you even want to know what can't be done? What is it that you would like to do with Python? If you want a one size fits all language you may be looking for a very long time... -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
qwe rty wrote: i know that an interpreted language like python can't be used to make an operating system or system drivers. As long as you are willing to write the OS hooks in C, you can write the userspace device drivers in Python: https://www.linuxquestions.org/questions/programming-9/how-to-write-device-driver-program-using-python-in-linux-687277/ Since Python is Turing-complete, there's no reason a whole OS couldn't be authored in Python. what else can NOT be done in python? what are the limitations of the language? I understand there's a little trouble getting Python to prove that P=NP You'll also find that it only comes close to solving the unrestricted three-body problem and the Traveling Salesman problem is still limited to fallible heuristics and searching the entire solution set in better than O(2**n) time. -tkc -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
what else can NOT be done in python? what are the limitations of the language? I understand there's a little trouble getting Python to prove that P=NP You'll also find that it only comes close to solving the unrestricted three-body problem and the Traveling Salesman problem is still limited to fallible heuristics and searching the entire solution set in better than O(2**n) time. I forgot about solving the Spam problem entirely. And answering poorly worded/thought-out questions on the internet... I've also been sorely disappointed by Python's ability to make a good chocolate cream silk pie. -tkc -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Aug 29, 3:14 am, Tim Chase python.l...@tim.thechases.com wrote: what else can NOT be done in python? what are the limitations of the language? I understand there's a little trouble getting Python to prove that P=NP You'll also find that it only comes close to solving the unrestricted three-body problem and the Traveling Salesman problem is still limited to fallible heuristics and searching the entire solution set in better than O(2**n) time. I forgot about solving the Spam problem entirely. And answering poorly worded/thought-out questions on the internet... I've also been sorely disappointed by Python's ability to make a good chocolate cream silk pie. -tkc if you don't know the answer please don't reply -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Aug 28, 7:05 pm, Tim Chase python.l...@tim.thechases.com wrote: (snip) Since Python is Turing-complete, there's no reason a whole OS couldn't be authored in Python. Yes, and one could go from NY to LA on a unicycle but would one really want to? Talk about some redass and blueballs! *yikes* Yes, if i have learned anything in my life, i can say there are absolutely no boundaries to what humans can achieve short the limit of their own imagination and the ever fading remainder of ones life. -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Fri, 28 Aug 2009 15:37:46 -0700, qwe rty wrote: i know that an interpreted language like python Languages are neither interpreted nor compiled. *Implementations* are interpreted or compiled. Perl has only one implementation, which is interpreted (as far as I know); Java has a number of implementations, some of which compile to byte-code, some compile to machine-code. There are C interpreters as well as C compilers. And languages like Forth have an unusual programming model which doesn't easily match the conventional interpreted/compiled distinction. Python has a number of implementations, all of which are compiled to byte- code, like early Java. None are purely interpreted; none are compiled to machine-code, although there are add-ons to CPython which will compile most Python code to machine-code. Some day, Python may include implementations which compile directly to machine-code. can't be used to make an operating system or system drivers. With existing Python implementations, it would be difficult to write an OS, because the implementations assume there is already an operating system available to handle things like memory and disk IO. So before you could write an OS in Python, you would need to write a new Python implementation. However, you could easily write a virtual OS in Python which sat on top of the regular OS. Device drivers would be less difficult, but performance may be slow compared to drivers written in (say) C. Boot loaders are another type of software which would be impractical to write in existing Python implementations. what else can NOT be done in python? what are the limitations of the language? As a language, Python has no theoretical limits -- it is Turing Complete, which means anything you can do in C, Java, Lisp, or any other Turing Complete language, you could do in Python -- with sufficient effort, and provided you don't care about efficiency. In practice, though, we *do* care about efficiency, and about the effort required to write the program in the first case. In practical terms, Python the language makes most things easy to write but slower to run, so there are very few applications which couldn't be written in Python. A few things are more difficult than others. One of the hardest things to do is to sandbox some arbitrary Python code from an untrusted source and execute it in a restricted environment. In practical terms, Python will let you write nearly any sort of program you want, provided absolute performance isn't your provided. (To put it another way, Python code is rarely the fastest, but it is usually fast enough.) If performance is too slow, Python is an excellent glue language, letting you write the bulk of your program in Python for ease, the performance-critical parts in C for speed. Some practical restrictions... if you are writing a web app, some hosting providers don't provide access to Python on their webserver, so you're limited to using whatever languages they provide, or finding another provider. All existing Python implementations require a minimum amount of memory to operate. This is relatively high, so you probably couldn't use Python on a device where you only had (say) 64K of memory. There's no Python implementation for your ancient Mac Plus or Commodore 64, and there probably never will be. Python the language is based on an execution model with relatively high overhead, so even if you wrote an implementation for such ancient machines, you probably couldn't do much with it. Existing Python implementations don't give you direct access to hardware, and bit-manipulation has a lot of overhead in Python. Numerical calculations (e.g. scientific array calculations) also suffer from overhead, which is barely noticeable if you're doing a few thousand calculations, but if you're doing a few tens of millions may be a little slow. For these, you should use Python as an interface to numeric libraries written in C, like Scipy and Numpy. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
qwe rty hkh00...@gmail.com wrote in message news:00a36f89-52dd-4d90-a455-cee6a0c9d...@q5g2000yqh.googlegroups.com... i know that an interpreted language like python can't be used to make an operating system or system drivers. what else can NOT be done in python? what are the limitations of the language? It's a floor wax and a dessert topping too! :-) -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
qwe rty wrote: On Aug 29, 3:14 am, Tim Chase python.l...@tim.thechases.com wrote: what else can NOT be done in python? what are the limitations of the language? I understand there's a little trouble getting Python to prove that P=NP You'll also find that it only comes close to solving the unrestricted three-body problem and the Traveling Salesman problem is still limited to fallible heuristics and searching the entire solution set in better than O(2**n) time. I forgot about solving the Spam problem entirely. And answering poorly worded/thought-out questions on the internet... I've also been sorely disappointed by Python's ability to make a good chocolate cream silk pie. if you don't know the answer please don't reply I'm not sure you understand -- Being a Turing complete language, anything you can do in any other language, you can do in Python. As r observed, it might not be a pleasant experience (though there are a lot of things I'd rather do in Python than in C or Assembly) but certainly doable. So clearly the issue resides in your nonsensical question. You asked for things you can't do with Python so I listed some. The things you can't do in Python are things you can't do in any other language either. To turn your snark on end, If you can't post a sensible question, please don't post in the first place. But this is usenet, and Python can't solve the problem of nonsensical questions posted on usenet. :-/ -tkc -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
if you don't know the answer please don't reply I'm not sure you understand -- Being a Turing complete language, anything you can do in any other language, you can do in Python. As r observed, it might not be a pleasant experience (though there are a lot of things I'd rather do in Python than in C or Assembly) but certainly doable. So clearly the issue resides in your nonsensical question. You asked for things you can't do with Python so I listed some. The things you can't do in Python are things you can't do in any other language either. To turn your snark on end, If you can't post a sensible question, please don't post in the first place. But this is usenet, and Python can't solve the problem of nonsensical questions posted on usenet. :-/ -tkc i am free to post , you are free to ignore -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Aug 29, 4:17 am, Steven D'Aprano st...@remove-this- cybersource.com.au wrote: On Fri, 28 Aug 2009 15:37:46 -0700, qwe rty wrote: i know that an interpreted language like python Languages are neither interpreted nor compiled. *Implementations* are interpreted or compiled. Perl has only one implementation, which is interpreted (as far as I know); Java has a number of implementations, some of which compile to byte-code, some compile to machine-code. There are C interpreters as well as C compilers. And languages like Forth have an unusual programming model which doesn't easily match the conventional interpreted/compiled distinction. Python has a number of implementations, all of which are compiled to byte- code, like early Java. None are purely interpreted; none are compiled to machine-code, although there are add-ons to CPython which will compile most Python code to machine-code. Some day, Python may include implementations which compile directly to machine-code. can't be used to make an operating system or system drivers. With existing Python implementations, it would be difficult to write an OS, because the implementations assume there is already an operating system available to handle things like memory and disk IO. So before you could write an OS in Python, you would need to write a new Python implementation. However, you could easily write a virtual OS in Python which sat on top of the regular OS. Device drivers would be less difficult, but performance may be slow compared to drivers written in (say) C. Boot loaders are another type of software which would be impractical to write in existing Python implementations. what else can NOT be done in python? what are the limitations of the language? As a language, Python has no theoretical limits -- it is Turing Complete, which means anything you can do in C, Java, Lisp, or any other Turing Complete language, you could do in Python -- with sufficient effort, and provided you don't care about efficiency. In practice, though, we *do* care about efficiency, and about the effort required to write the program in the first case. In practical terms, Python the language makes most things easy to write but slower to run, so there are very few applications which couldn't be written in Python. A few things are more difficult than others. One of the hardest things to do is to sandbox some arbitrary Python code from an untrusted source and execute it in a restricted environment. In practical terms, Python will let you write nearly any sort of program you want, provided absolute performance isn't your provided. (To put it another way, Python code is rarely the fastest, but it is usually fast enough.) If performance is too slow, Python is an excellent glue language, letting you write the bulk of your program in Python for ease, the performance-critical parts in C for speed. Some practical restrictions... if you are writing a web app, some hosting providers don't provide access to Python on their webserver, so you're limited to using whatever languages they provide, or finding another provider. All existing Python implementations require a minimum amount of memory to operate. This is relatively high, so you probably couldn't use Python on a device where you only had (say) 64K of memory. There's no Python implementation for your ancient Mac Plus or Commodore 64, and there probably never will be. Python the language is based on an execution model with relatively high overhead, so even if you wrote an implementation for such ancient machines, you probably couldn't do much with it. Existing Python implementations don't give you direct access to hardware, and bit-manipulation has a lot of overhead in Python. Numerical calculations (e.g. scientific array calculations) also suffer from overhead, which is barely noticeable if you're doing a few thousand calculations, but if you're doing a few tens of millions may be a little slow. For these, you should use Python as an interface to numeric libraries written in C, like Scipy and Numpy. -- Steven thank you very much ,THIS is the sort of answer i wanted -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Fri, 28 Aug 2009 17:31:22 -0700, r wrote: Since Python is Turing-complete, there's no reason a whole OS couldn't be authored in Python. Yes, and one could go from NY to LA on a unicycle but would one really want to? Talk about some redass and blueballs! *yikes* Yes, if i have learned anything in my life, i can say there are absolutely no boundaries to what humans can achieve short the limit of their own imagination and the ever fading remainder of ones life. Well, other than writing a program to determine whether a program in a Turing-complete language will terminate on some input, or devising a formal system which is sound, complete, and able to express its own metatheory, or ... Some things are actually impossible. -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Fri, 28 Aug 2009 17:26:06 -0700, qwe rty wrote: if you don't know the answer please don't reply If you don't understand the question, don't post it in the first place. -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Aug 29, 5:11 am, Nobody nob...@nowhere.com wrote: On Fri, 28 Aug 2009 17:26:06 -0700, qwe rty wrote: if you don't know the answer please don't reply If you don't understand the question, don't post it in the first place. don't be so angry ,not good for your health -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Fri, 28 Aug 2009, qwe rty wrote: i know that an interpreted language like python can't be used to make an operating system or system drivers. what else can NOT be done in python? what are the limitations of the language? Oh, my. And now everybody points at you this Turing-completeness. The issue, in my opinion, is not that something cannot be done. The truth about Turing-completeness is, I would say, you can do whatever but sometimes you will not because it would be too ugly. My private list of things that when implemented in Python would be ugly to the point of calling it difficult: 1. AMB operator - my very favourite. In one sentence, either language allows one to do it easily or one would not want to do it (in an ugly way). http://www.randomhacks.net/articles/2005/10/11/amb-operator After quite some googling I was finally able to locate sample implementation, but I cannot say ATM how well it works and if it is practical enough to use it in any of my programs. If time permits, I will try it, hopefully. http://www.c2.com/cgi/wiki?AmbInPython 2. Changing the language from the inside. Everybody can change the interpreter, right? But how about doing some bigger, maybe even fundamental change to the language by means offered by the language itself? Example: If Python had no object system, or if I wanted to implement one in different way (say, I would like to experiment or I would not want to wait for a new release). In some languages that interest me now, it is possible and practical, more or less. So it can sometimes backfire - what OO system should I choose for my next Scheme program, etc. Because there are few of them :-), all (? - I believe) implemented as a code library. Just install it and off you go, now you have OO programming. Actually, I don't use OO all that much recently (maybe I feel disapointed a bit, or something). Also, I have read (but not checked it myself) that for some time Common Lisp had it's now-official CLOS distributed and tested in a form of library. Say, have they adopted OO with single inheritance as a part of CL ANSI standard - I would still be able to have OO with multiple inheritance. I would just have to download and install CLOS. No change to interpreter or compiler. From their point of view, CLOS would be just another library. http://en.wikipedia.org/wiki/Common_Lisp_Object_System Judging by this code, introducing OO to the language is relatively easy: http://www.ccs.neu.edu/home/dorai/t-y-scheme/t-y-scheme-Z-H-14.html It is not possible to alter Python in a minor way, I think. Something simpler than OO, like a new keyword or structures: http://www.ccs.neu.edu/home/dorai/t-y-scheme/t-y-scheme-Z-H-10.html http://www.ccs.neu.edu/home/dorai/t-y-scheme/t-y-scheme-Z-H-11.html Some readers could oppose the above by saying that Lisp's syntax is so primitive that it can be used to implement just any programming paradigm, so having it as a loadable code is not a big achievement. Well, it seems to me that Python has even simpler syntax or on par with Lisp family, so... Some (perhaps other) readers could also say, that there is no need to extend Python. It already has sets and yield and... But some time ago it did not. As far as I can tell, it can be a bit too hard to go into experimenting mode with Python. Something like adding yield all but myself. It only takes few kilos of code for a working OO in another language, so how hard could such yield be? Well, in Python I probably wouldn't dare. BTW I hope nobody's feeling have been hurt. This was meant to be informative, not offensive. BTW2. As I said, these are _possible_ things (Turing complete language, and so on). But adding them would require some hard work and would produce ugly and/or fragile code, so I decided it could be easier to learn another language... Regards, Tomasz Rola -- ** A C programmer asked whether computer had Buddha's nature. ** ** As the answer, master did rm -rif on the programmer's home** ** directory. And then the C programmer became enlightened... ** ** ** ** Tomasz Rola mailto:tomasz_r...@bigfoot.com ** -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
In article bbe16797-95c6-4fc3-89d5-8d69c4744...@f10g2000vbf.googlegroups.com, qwe rty hkh00...@gmail.com wrote: if you don't know the answer please don't reply I'm not sure you understand -- Being a Turing complete language, anything you can do in any other language, you can do in Python. =A0 As r observed, it might not be a pleasant experience (though there are a lot of things I'd rather do in Python than in C or Assembly) but certainly doable. So clearly the issue resides in your nonsensical question. =A0You asked for things you can't do with Python so I listed some. =A0The things you can't do in Python are things you can't do in any other language either. =A0To turn your snark on end, If you can't post a sensible question, please don't post in the first place. But this is usenet, and Python can't solve the problem of nonsensical questions posted on usenet. :-/ -tkc i am free to post , you are free to ignore Well -- don't you think the same applies in reverse? Remember that Python is named after the comedy group Monty Python, and jokes are a frequent occurrence on this group. -- Aahz (a...@pythoncraft.com) * http://www.pythoncraft.com/ I support family values -- Addams family values --www.nancybuttons.com -- http://mail.python.org/mailman/listinfo/python-list
Re: What python can NOT do?
On Sat, 29 Aug 2009 05:37:34 +0200, Tomasz Rola wrote: My private list of things that when implemented in Python would be ugly to the point of calling it difficult: 1. AMB operator - my very favourite. In one sentence, either language allows one to do it easily or one would not want to do it (in an ugly way). http://www.randomhacks.net/articles/2005/10/11/amb-operator Fascinating, but I don't exactly see how that's actually *useful*. It strikes me of combining all the benefits of COME FROM with the potential performance of Bogosort, but maybe I'm being harsh. On the other hand, it sounds rather like Prolog-like declarative programming. I fear that, like Prolog, it risks massive performance degradation if you don't apply the constraints in the right order. 2. Changing the language from the inside. Everybody can change the interpreter, right? But how about doing some bigger, maybe even fundamental change to the language by means offered by the language itself? Like Forth. You need it in Forth, because it has a very sparse set of language features, and everything is bootstrapped from a small set of commands, so the ability to re-define the language as you go is (1) necessary and (2) free. But for Python, I don't know... it sounds cool, but in practice? It sounds like the sort of thing that allows programmers to spend three hours writing a new control structure which will save them three minutes. And of course, for all but the tiniest, one-man-band applications, readability is important. Sure, you've created a gee-whizz control structure which combines try, while and if into one keyword, and it automatically does logging and threading, fantastic. But how will anyone else be able to maintain it when you're gone? The ability to change the language is one step into a tarpit, where everything is possible but nothing is easy, and where you spend all your time writing language features and none of your time building the useful functionality you actually want. It sounds like something you want in a language you use for designing languages, rather than writing applications. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
