Re: function v. method
Gerhard Fiedler [EMAIL PROTECTED] wrote: On 2006-07-25 05:16:04, Wesley Brooks wrote: prefix your names with _ or __. Both are ommited from autogenerated docuementation and both are OFFICALLY not supposed to be used. Could you elaborate on that a little or point me in the right direction to read up on it? I'm currently re-writing a large lump of my coding and trying to use best practice. I thought it was considered good practice to make stuff private (in this case using __ ) that wasn't intened to be accessed from outside the function/class? I think fuzzylollipop meant that such members should not be used from the outside of the class; that is, they should be considered implementation, not API. (Which is why apparently autogenerated docs leave them out.) Unfortunately, there is a slight ambiguity here. Consider for example the wonderful Queue class. Its methods _put, _get are not documented in help(Queue.Queue) nor on http://docs.python.org/lib/QueueObjects.html, respecting the private convention. But if you read Queue.py, you'll see...: # Override these methods to implement other queue organizations # (e.g. stack or priority queue). # These will only be called with appropriate locks held ... # Put a new item in the queue def _put(self, item): ... etc -- i.e., Queue.py itself strongly appears to consider these methods *protected* (in C++ parlance), NOT *private*. Indeed, the only reason these methods are factored out is exactly as hook methods (meant to be overridden by subclasses), in a beautiful example of the Template Method design pattern (in the specific variant in which the methods MAY but DON'T HAVE TO be overridden, because the base class, Queue.Queue, already provides them with useful functionality -- a LIFO queue). Unfortunately Python does not have any specific naming convention to indicate methods that should never be CALLED by client code, but may be usefully OVERRIDDEN in subclasses, so the leading-underscore one does double duty -- and since the simpler interpretation this is a private implementation detail, ignore it completely is so much more common than the one about this is a hook method which you should override in a subclass if you want to tweak some detail of functionality, it's all too easy to forget about the latter case (fortunately Queue.Queue is there to remind us of it:-). Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
(Apollogies to fuzzylollipop for replying to them rather than the list!)Python does have ALREADY have an OFFICAL mechanism for private members, prefix your names with _ or __. Both are ommited from autogenerateddocuementation and both are OFFICALLY not supposed to be used.Could you elaborate on that a little or point me in the right direction to read up on it? I'm currently re-writing a large lump of my coding and trying to use best practice. I thought it was considered good practice to make stuff private (in this case using __ ) that wasn't intened to be accessed from outside the function/class? Cheers for your help.Wesley Brooks. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
On 2006-07-25 05:16:04, Wesley Brooks wrote: prefix your names with _ or __. Both are ommited from autogenerated docuementation and both are OFFICALLY not supposed to be used. Could you elaborate on that a little or point me in the right direction to read up on it? I'm currently re-writing a large lump of my coding and trying to use best practice. I thought it was considered good practice to make stuff private (in this case using __ ) that wasn't intened to be accessed from outside the function/class? I think fuzzylollipop meant that such members should not be used from the outside of the class; that is, they should be considered implementation, not API. (Which is why apparently autogenerated docs leave them out.) Gerhard -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
Antoon Pardon wrote:
On 2006-07-21, Bruno Desthuilliers [EMAIL PROTECTED] wrote:
Antoon Pardon wrote:
On 2006-07-21, fuzzylollipop [EMAIL PROTECTED] wrote:
danielx wrote:
(snip)
if you prefix with a single underscore, that tells the user, DON'T MESS
WITH ME FROM OUTSIDE! I AM AN IMPLEMENTATION DETAIL!
Personnaly I don't like this convention.
To bad for you.
I'll survive.
It isn't clear enough.
Oh yes ?
Suppose I am writing my own module, I use an underscore, to
mark variables which are an implementation detail for my
module.
Now I need to import an other module in my module and need access
to an implementation variable from that module.
So now I have
variables with an underscore which have two different meanings:
1) This is an implemantation detail of this module, It is the
users of my module who have to be extra carefull using it.
2) This is an implemantation detail of the other module,
I should be extra carefull using it.
Either you imported with the from othermodule import * form (which you
shouldn't do), and you *don't* have the implementation of othermodule,
or your used the import othermodule form, in which case it's pretty
obvious which names belongs to othermodule.
As far as I understand the _name convention is often defended with the
argument that it stands out.
It does.
Now if you have to go and look at the
import statements to make a disticntion, then it seems that the
way _names standout isn't that usefull.
Please re-read the Fine Manual and try to understand what I wrote above.
You don't have to parse the import statements to know if you're dealing
with a local implementation detail or implementation of another module,
unless you do braindead renames of imported symbols.
Anyway, messing with another module's implementation should be *very* rare.
And I find variable starting or ending with an underscore ugly. :-)
Too bad for you. Choose another language then... PHP, Perl, Ruby ?-)
Not a very strong argument. Whether or not someone has a legitimat point
of criticism against Python or some of the conventions used. You can
always reply: Too bad, better choose another language then.
There are very few chances this convention will change anytime soon. You
may not like it for any good or bad reason, the fact is that you have to
live with it.
FWIW, the choice of other languages I proposed as an alternative is not
totally innocent : they all are possible replacements for Python, and
they all have their share of ugly cryptic notations... I'm not myself a
big fan of the leading underscore, but it's certainly a lesser evil when
compared to $php_vars or others @myperlishstuff. Or with C++
m_myMemberVar FWIW.
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
--
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Re: function v. method
Antoon Pardon wrote:
On 2006-07-21, fuzzylollipop [EMAIL PROTECTED] wrote:
Antoon Pardon wrote:
Suppose I am writing my own module, I use an underscore, to
mark variables which are an implementation detail for my
module.
Now I need to import an other module in my module and need access
to an implementation variable from that module. So now I have
variables with an underscore which have two different meanings:
you don't understand what implementation detail means, it means it is
NOT part of the public API and no client code should ever use it.
If you reference _vara in your code and it is in someone elses module
you don't understand YOU ARE NOT SUPPOSED TO DO THAT!
Why do you assume that in my example the other module is
not understood?
He doesn't, but it's clear that *you* didn't understand what
fuzzylollipop meant !-)
Hint : add a comma at the right place so parsing is unambigous:
If you reference _vara in your code and it is in someone elses module,
you don't understand YOU ARE NOT SUPPOSED TO DO THAT!
1) This is an implemantation detail of this module, It is the
users of my module who have to be extra carefull using it.
Users of your module should NEVER KNOW any of the _ or __ stuff exists
to begin with.
2) This is an implemantation detail of the other module,
I should be extra carefull using it.
You should NEVER use it.
Well that may be your view, but AFAICS it is not the view of
the python community. Because each time some mechanism is
proposed for real private variable, people oppose it, they
want people to have access to what are supposed to be
private variables.
I'd express it in a somewhat different way: the view of the Python
community is that language-inforced access restrictions are useless and
annoying, IOW an unnecessary pain. Which doesn't imply that messing with
implementation of other modules is actually *encouraged*. Having the
possibility to easily do so is quite handy when that's the only/less
worse solution, but is not a recommended approach in general.
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
--
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Re: function v. method
Gerhard Fiedler wrote: On 2006-07-22 16:32:38, danielx wrote: ...and source code... *shudders* What happened to all the goodness of abstraction? Abstraction as you seem to use it requires complete docs of the interface. Which is what you said you don't have... So the original abstractor broke the abstraction when publishing insufficient docs, not the one who looks into the sources to find out what actually happens. Absolutely. I didn't mean the user was breaking abstraction (let's not blame the victim). I was saying that we should really have more sympathy for him. I have all the sympathy in the world for him... after all, he's me :) But one reason why I try to write (and insist on as much as possible from people writing for or with me) self-documenting code is that wherever you have documentation and code separated (which is the case of API docs), you can bet (without losing) that sooner or later code and doc will diverge. This has a probability that approaches 1 :) So, I agree with you that good API docs are a good thing, as they tell me everything I need to know without having to wade through tons of implementation details that may be interesting but don't serve my immediate need (of having to use the API). But reality seems to be (and mine so far definitely is) that these docs, even the good ones, are not completely in alignment with the reality of the code. (We all know that code has bugs... and the API always describes, at best, how the code /should/ work. It never describes how it actually works, including the bugs g (this notwithstanding the bugs that have been elevated to features and henceforth been described in the API docs). So... the final authority /is/ the code. I don't see an alternative. For me, good abstraction doesn't mean I don't have to read the sources; good abstraction means (among other things) that I can read the sources easily. Gerhard having auto generated docs, which means the documentatin is in the code as doc strings, javadoc, reflex, or whatever format is the BEST way of doing API documentation, period. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
Antoon Pardon wrote: On 2006-07-21, fuzzylollipop [EMAIL PROTECTED] wrote: Antoon Pardon wrote: Suppose I am writing my own module, I use an underscore, to mark variables which are an implementation detail for my module. Now I need to import an other module in my module and need access to an implementation variable from that module. So now I have variables with an underscore which have two different meanings: you don't understand what implementation detail means, it means it is NOT part of the public API and no client code should ever use it. If you reference _vara in your code and it is in someone elses module you don't understand YOU ARE NOT SUPPOSED TO DO THAT! Why do you assume that in my example the other module is not understood? 1) This is an implemantation detail of this module, It is the users of my module who have to be extra carefull using it. Users of your module should NEVER KNOW any of the _ or __ stuff exists to begin with. 2) This is an implemantation detail of the other module, I should be extra carefull using it. You should NEVER use it. Well that may be your view, but AFAICS it is not the view of the python community. Because each time some mechanism is proposed for real private variable, people oppose it, they want people to have access to what are supposed to be private variables. -- Antoon Pardon actually you are really way off base, the _ and __ convention IS the INTENDED way of doing private and really private documentation of members in Python. I didn't make this up, it is in the official Python documentation. You need to read my previous response for COMPREHENSION one more time. There is LESS THAN ZERO value in having a runtime enforcement of member access control. Python does have ALREADY have an OFFICAL mechanism for private members, prefix your names with _ or __. Both are ommited from autogenerated docuementation and both are OFFICALLY not supposed to be used. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
On 2006-07-24 13:25:14, fuzzylollipop wrote: So... the final authority /is/ the code. I don't see an alternative. For me, good abstraction doesn't mean I don't have to read the sources; good abstraction means (among other things) that I can read the sources easily. having auto generated docs, which means the documentatin is in the code as doc strings, javadoc, reflex, or whatever format is the BEST way of doing API documentation, period. It may be the best way, no contest to that. But it still is not the code. (I actually think that possibly the current way of embedding javadoc-like documentation into sources is only a stepping stone into the direction generally pointed to by what Wirth called literate programming. In any case, I'd rather not call it the best way, period; calling it the best currently widely supported way seems more appropriate to me.) Even doc strings tend to get out of sync with the code. And even doc strings document (at best) what the code should do, not what it actually does. And even doc strings are not always complete in describing the functionality. So auto generated docs are also incomplete and out of sync with the code, sometimes more, sometimes less, sometimes so little that it is not relevant. But you can't know how much out of sync they are from reading the docs alone. So when push comes to shove (or so the saying goes? :), the code is the authority. Even with auto generated docs. Period... ?!? g Gerhard -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
On 2006-07-24 14:41:02, Gerhard Fiedler wrote: (I actually think that possibly the current way of embedding javadoc-like documentation into sources is only a stepping stone into the direction generally pointed to by what Wirth called literate programming. That was Knuth, not Wirth. But this is not really that relevant. Gerhard -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
On 2006-07-21, Bruno Desthuilliers [EMAIL PROTECTED] wrote: Antoon Pardon wrote: On 2006-07-21, fuzzylollipop [EMAIL PROTECTED] wrote: danielx wrote: (snip) if you prefix with a single underscore, that tells the user, DON'T MESS WITH ME FROM OUTSIDE! I AM AN IMPLEMENTATION DETAIL! Personnaly I don't like this convention. To bad for you. I'll survive. It isn't clear enough. Oh yes ? Suppose I am writing my own module, I use an underscore, to mark variables which are an implementation detail for my module. Now I need to import an other module in my module and need access to an implementation variable from that module. So now I have variables with an underscore which have two different meanings: 1) This is an implemantation detail of this module, It is the users of my module who have to be extra carefull using it. 2) This is an implemantation detail of the other module, I should be extra carefull using it. Either you imported with the from othermodule import * form (which you shouldn't do), and you *don't* have the implementation of othermodule, or your used the import othermodule form, in which case it's pretty obvious which names belongs to othermodule. As far as I understand the _name convention is often defended with the argument that it stands out. Now if you have to go and look at the import statements to make a disticntion, then it seems that the way _names standout isn't that usefull. And I find variable starting or ending with an underscore ugly. :-) Too bad for you. Choose another language then... PHP, Perl, Ruby ?-) Not a very strong argument. Whether or not someone has a legitimat point of criticism against Python or some of the conventions used. You can always reply: Too bad, better choose another language then. -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
On 2006-07-21, fuzzylollipop [EMAIL PROTECTED] wrote: Antoon Pardon wrote: Suppose I am writing my own module, I use an underscore, to mark variables which are an implementation detail for my module. Now I need to import an other module in my module and need access to an implementation variable from that module. So now I have variables with an underscore which have two different meanings: you don't understand what implementation detail means, it means it is NOT part of the public API and no client code should ever use it. If you reference _vara in your code and it is in someone elses module you don't understand YOU ARE NOT SUPPOSED TO DO THAT! Why do you assume that in my example the other module is not understood? 1) This is an implemantation detail of this module, It is the users of my module who have to be extra carefull using it. Users of your module should NEVER KNOW any of the _ or __ stuff exists to begin with. 2) This is an implemantation detail of the other module, I should be extra carefull using it. You should NEVER use it. Well that may be your view, but AFAICS it is not the view of the python community. Because each time some mechanism is proposed for real private variable, people oppose it, they want people to have access to what are supposed to be private variables. -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
On 2006-07-22 16:32:38, danielx wrote: ...and source code... *shudders* What happened to all the goodness of abstraction? Abstraction as you seem to use it requires complete docs of the interface. Which is what you said you don't have... So the original abstractor broke the abstraction when publishing insufficient docs, not the one who looks into the sources to find out what actually happens. Absolutely. I didn't mean the user was breaking abstraction (let's not blame the victim). I was saying that we should really have more sympathy for him. I have all the sympathy in the world for him... after all, he's me :) But one reason why I try to write (and insist on as much as possible from people writing for or with me) self-documenting code is that wherever you have documentation and code separated (which is the case of API docs), you can bet (without losing) that sooner or later code and doc will diverge. This has a probability that approaches 1 :) So, I agree with you that good API docs are a good thing, as they tell me everything I need to know without having to wade through tons of implementation details that may be interesting but don't serve my immediate need (of having to use the API). But reality seems to be (and mine so far definitely is) that these docs, even the good ones, are not completely in alignment with the reality of the code. (We all know that code has bugs... and the API always describes, at best, how the code /should/ work. It never describes how it actually works, including the bugs g (this notwithstanding the bugs that have been elevated to features and henceforth been described in the API docs). So... the final authority /is/ the code. I don't see an alternative. For me, good abstraction doesn't mean I don't have to read the sources; good abstraction means (among other things) that I can read the sources easily. Gerhard -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
Bruno Desthuilliers wrote:
danielx wrote:
Bruno Desthuilliers wrote:
danielx wrote:
(snip)
Obviously, such things would be omitted from your docs, but users also
learn by interacting with Python, which is really one of Python's great
virtues. When supporting documents aren't sufficient to learn an api
(I'm sure this never happens, so just humor me), you can always turn to
interactive Python.
...and source code...
*shudders* What happened to all the goodness of abstraction?
Compared to machine language, Python source code is really abstration.
And machine language is an abstraction of pushing electrons around
circuits. I'm not sure I see your point, unless it is simply that
Python is easier than asm.
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
--
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Re: function v. method
Gerhard Fiedler wrote: On 2006-07-20 18:10:21, danielx wrote: When supporting documents aren't sufficient to learn an api (I'm sure this never happens, so just humor me), you can always turn to interactive Python. ...and source code... *shudders* What happened to all the goodness of abstraction? Abstraction as you seem to use it requires complete docs of the interface. Which is what you said you don't have... So the original abstractor broke the abstraction when publishing insufficient docs, not the one who looks into the sources to find out what actually happens. Absolutely. I didn't mean the user was breaking abstraction (let's not blame the victim). I was saying that we should really have more sympathy for him. (This independently of the merits of abstraction.) Gerhard -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
danielx a écrit : Bruno Desthuilliers wrote: danielx wrote: Bruno Desthuilliers wrote: danielx wrote: (snip) Obviously, such things would be omitted from your docs, but users also learn by interacting with Python, which is really one of Python's great virtues. When supporting documents aren't sufficient to learn an api (I'm sure this never happens, so just humor me), you can always turn to interactive Python. ...and source code... *shudders* What happened to all the goodness of abstraction? Compared to machine language, Python source code is really abstration. And machine language is an abstraction of pushing electrons around circuits. I'm not sure I see your point, unless it is simply that Python is easier than asm. Python is very hi-level, and very often well-written Python code is it's own better documentation. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
fuzzylollipop wrote: danielx wrote: Bruno Desthuilliers wrote: danielx wrote: At first I was going to post the following: !-- beginning of my original post -- (snip) !-- end of my original post, with ending censored -- but then I tried this: res = Foo.__dict__['func'] res is dan True And it all started to make sense. The surprising thing turned out to be not so surprising: When the expression Foo.func gets evaluated, we get a method which is just a wrapper around dan. Therefore, f is not dan! This is still a little bit of magic, FWIW, the function class implements the descriptor protocol... Here's the magic. which gets me thinking again about the stuff I self-censored. Since the dot syntax does something special and unexpected in my case, unexpected ? Did you ever wondered how the instance or class was passed as first arg when doing method calls ? Not knowing what's going on during method calls is exactly what motivated me to post. why not use some more dot-magic to implement privates? What for ? What makes you think we need language-inforced access restriction ? I knew someone would bring this up. The motivation would not be to provide restriction, but to help maintain clean api's. If you intended for users to use only a subset of the methods in your class, why not help them learn your api by presenting the stuff they can use not along side the stuff they should not? Obviously, such things would be omitted from your docs, but users also learn by interacting with Python, which is really one of Python's great virtues. When supporting documents aren't sufficient to learn an api (I'm sure this never happens, so just humor me), you can always turn to interactive Python. This is exactly what it's there for. If nothing is hidden, a user could be easily mislead to believe he can use a method when he really shouldn't. if you prefix with a single underscore, that tells the user, DON'T MESS WITH ME FROM OUTSIDE! I AM AN IMPLEMENTATION DETAIL! and it gets ommited from all the doc generation if you prefix with a double underscore, then they have to go even FARTHER out of their way to shoot themselves in the foot. Python takes the stance of personal responsiblity when it comes to access control. Which in NO WAY dimishes its robustness or anything else. just read the DailyWTF.com, incompentent people will abuse any language features in any language, and will figure out how to break programatic access control no matter how it is implemented. Matter of fact, Java which in another thread someone was ADAMANT that did not expose private anything from reflection ( and was wrong ) specifically allows you to access all the private members, functions, everything. You just need to tell it to turn all the safeties off. From the api: public void setAccessible(boolean flag) throws SecurityException Set the accessible flag for this object to the indicated boolean value. A value of true indicates that the reflected object should suppress Java language access checking when it is used. A value of false indicates that the reflected object should enforce Java language access checks. Setting the accessible flag in a reflected object permits sophisticated applications with sufficient privilege, such as Java Object Serialization or other persistence mechanisms, to manipulate objects in a manner that would normally be prohibited. so anything added to Python to enforce access control would immediately be forced to provide some means to over-ride the checks for pickle and the like. Not to even mention the argument that it would break crap loads of existing code base. Sigh. I TOTALLY realize that Python works by politeness and not enforcement. I think you are misinterpreting why I think this would be a good idea. My concern is not with control, but with convenience. My suggestion was that privates would only be invisible if you use the dot syntax (ie if you are an external user); they would not be invisible altogether (they would still be in __dict__ with no name games). One problem which was brought up about this was that self.meth and outsider.meth would have to be interpretted differently. I suspect (but I haven't finished my reading assignment :P) that you could find a good way around this. With respect to breaking stuff. I'm not sure why that would be necessary. If current code does not say any member is private, everything that was visible before (ie everything) would still be visible after. Last thing. You mentioned that auto doc generation omits underscore-prefixed and name mangled members. dir on the other hand does not. Maybe this suggests only a minor future improvement. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
Bruno Desthuilliers wrote: danielx a écrit : Bruno Desthuilliers wrote: danielx wrote: Bruno Desthuilliers wrote: danielx wrote: (snip) Obviously, such things would be omitted from your docs, but users also learn by interacting with Python, which is really one of Python's great virtues. When supporting documents aren't sufficient to learn an api (I'm sure this never happens, so just humor me), you can always turn to interactive Python. ...and source code... *shudders* What happened to all the goodness of abstraction? Compared to machine language, Python source code is really abstration. And machine language is an abstraction of pushing electrons around circuits. I'm not sure I see your point, unless it is simply that Python is easier than asm. Python is very hi-level, and very often well-written Python code is it's own better documentation. Yes, Python is very easy to read, but who's supposed to be reading it? Maintainers or users? I'm really against code acting as its own documentation. Of course the code is authoritative, but should we really EXPECT it to serve as a reference to users?? Appearantly, this view puts me in the minority... -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
danielx a écrit : (snip) Sigh. I TOTALLY realize that Python works by politeness and not enforcement. I think you are misinterpreting why I think this would be a good idea. My concern is not with control, but with convenience. Having free access to implementation is convenient IMHO. My suggestion was that privates would only be invisible if you use the dot syntax (ie if you are an external user); they would not be invisible altogether (they would still be in __dict__ with no name games). How would this work for class attributes ? (implementation methods, implementation descriptors etc...) Also, it would impact lookup perfs, which is already a somewhat weak point in Python. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
Bruno Desthuilliers wrote: Antoon Pardon wrote: On 2006-07-21, fuzzylollipop [EMAIL PROTECTED] wrote: danielx wrote: (snip) if you prefix with a single underscore, that tells the user, DON'T MESS WITH ME FROM OUTSIDE! I AM AN IMPLEMENTATION DETAIL! Personnaly I don't like this convention. To bad for you. It isn't clear enough. Oh yes ? Suppose I am writing my own module, I use an underscore, to mark variables which are an implementation detail for my module. Now I need to import an other module in my module and need access to an implementation variable from that module. So now I have variables with an underscore which have two different meanings: 1) This is an implemantation detail of this module, It is the users of my module who have to be extra carefull using it. 2) This is an implemantation detail of the other module, I should be extra carefull using it. Either you imported with the from othermodule import * form (which you shouldn't do), and you *don't* have the implementation of othermodule, or your used the import othermodule form, in which case it's pretty obvious which names belongs to othermodule. Have any other, possibly valid, reason ? And I find variable starting or ending with an underscore ugly. :-) Too bad for you. Choose another language then... PHP, Perl, Ruby ?-) Too bad for you: While you have a valid point that this contention is really just arbitrary (just like all conventions), could we be a little gentler? Personally, I don't think it looks very good either, but you just have to deal with it if you're going to use the language properly. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
danielx a écrit : Bruno Desthuilliers wrote: danielx a écrit : Bruno Desthuilliers wrote: danielx wrote: Bruno Desthuilliers wrote: danielx wrote: (snip) Obviously, such things would be omitted from your docs, but users also learn by interacting with Python, which is really one of Python's great virtues. When supporting documents aren't sufficient to learn an api (I'm sure this never happens, so just humor me), you can always turn to interactive Python. ...and source code... *shudders* What happened to all the goodness of abstraction? Compared to machine language, Python source code is really abstration. And machine language is an abstraction of pushing electrons around circuits. I'm not sure I see your point, unless it is simply that Python is easier than asm. Python is very hi-level, and very often well-written Python code is it's own better documentation. Yes, Python is very easy to read, but who's supposed to be reading it? Maintainers or users? In an ideal world, nobody !-) I'm really against code acting as its own documentation. I'm really for it, because : Of course the code is authoritative, indeed. but should we really EXPECT it to serve as a reference to users?? Unless you're able to maintain a good, accurate and always up to date documentation, you can be sure users (ie other programmers) will turn to the code. Also, there are cases where even a pretty good doc is not enough, and you really have to turn to the code to know for sure how to best implement something. FWIW, reading source code can be very instructive... -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
Alex Martelli schrieb: danielx [EMAIL PROTECTED] wrote: ...and source code... *shudders* What happened to all the goodness of abstraction? http://www.joelonsoftware.com/articles/LeakyAbstractions.htm Misses an l at the end: http://www.joelonsoftware.com/articles/LeakyAbstractions.html Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
danielx wrote:
Bruno Desthuilliers wrote:
danielx wrote:
(snip)
Obviously, such things would be omitted from your docs, but users also
learn by interacting with Python, which is really one of Python's great
virtues. When supporting documents aren't sufficient to learn an api
(I'm sure this never happens, so just humor me), you can always turn to
interactive Python.
...and source code...
*shudders* What happened to all the goodness of abstraction?
Compared to machine language, Python source code is really abstration.
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
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Re: function v. method
On 2006-07-21, fuzzylollipop [EMAIL PROTECTED] wrote: danielx wrote: Bruno Desthuilliers wrote: danielx wrote: At first I was going to post the following: !-- beginning of my original post -- (snip) !-- end of my original post, with ending censored -- but then I tried this: res = Foo.__dict__['func'] res is dan True And it all started to make sense. The surprising thing turned out to be not so surprising: When the expression Foo.func gets evaluated, we get a method which is just a wrapper around dan. Therefore, f is not dan! This is still a little bit of magic, FWIW, the function class implements the descriptor protocol... Here's the magic. which gets me thinking again about the stuff I self-censored. Since the dot syntax does something special and unexpected in my case, unexpected ? Did you ever wondered how the instance or class was passed as first arg when doing method calls ? Not knowing what's going on during method calls is exactly what motivated me to post. why not use some more dot-magic to implement privates? What for ? What makes you think we need language-inforced access restriction ? I knew someone would bring this up. The motivation would not be to provide restriction, but to help maintain clean api's. If you intended for users to use only a subset of the methods in your class, why not help them learn your api by presenting the stuff they can use not along side the stuff they should not? Obviously, such things would be omitted from your docs, but users also learn by interacting with Python, which is really one of Python's great virtues. When supporting documents aren't sufficient to learn an api (I'm sure this never happens, so just humor me), you can always turn to interactive Python. This is exactly what it's there for. If nothing is hidden, a user could be easily mislead to believe he can use a method when he really shouldn't. if you prefix with a single underscore, that tells the user, DON'T MESS WITH ME FROM OUTSIDE! I AM AN IMPLEMENTATION DETAIL! Personnaly I don't like this convention. It isn't clear enough. Suppose I am writing my own module, I use an underscore, to mark variables which are an implementation detail for my module. Now I need to import an other module in my module and need access to an implementation variable from that module. So now I have variables with an underscore which have two different meanings: 1) This is an implemantation detail of this module, It is the users of my module who have to be extra carefull using it. 2) This is an implemantation detail of the other module, I should be extra carefull using it. And I find variable starting or ending with an underscore ugly. :-) -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
Antoon Pardon wrote:
On 2006-07-21, fuzzylollipop [EMAIL PROTECTED] wrote:
danielx wrote:
(snip)
if you prefix with a single underscore, that tells the user, DON'T MESS
WITH ME FROM OUTSIDE! I AM AN IMPLEMENTATION DETAIL!
Personnaly I don't like this convention.
To bad for you.
It isn't clear enough.
Oh yes ?
Suppose I am writing my own module, I use an underscore, to
mark variables which are an implementation detail for my
module.
Now I need to import an other module in my module and need access
to an implementation variable from that module.
So now I have
variables with an underscore which have two different meanings:
1) This is an implemantation detail of this module, It is the
users of my module who have to be extra carefull using it.
2) This is an implemantation detail of the other module,
I should be extra carefull using it.
Either you imported with the from othermodule import * form (which you
shouldn't do), and you *don't* have the implementation of othermodule,
or your used the import othermodule form, in which case it's pretty
obvious which names belongs to othermodule.
Have any other, possibly valid, reason ?
And I find variable starting or ending with an underscore ugly. :-)
Too bad for you. Choose another language then... PHP, Perl, Ruby ?-)
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
--
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Re: function v. method
On 2006-07-20 18:10:21, danielx wrote: When supporting documents aren't sufficient to learn an api (I'm sure this never happens, so just humor me), you can always turn to interactive Python. ...and source code... *shudders* What happened to all the goodness of abstraction? Abstraction as you seem to use it requires complete docs of the interface. Which is what you said you don't have... So the original abstractor broke the abstraction when publishing insufficient docs, not the one who looks into the sources to find out what actually happens. (This independently of the merits of abstraction.) Gerhard -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
Antoon Pardon wrote: Suppose I am writing my own module, I use an underscore, to mark variables which are an implementation detail for my module. Now I need to import an other module in my module and need access to an implementation variable from that module. So now I have variables with an underscore which have two different meanings: you don't understand what implementation detail means, it means it is NOT part of the public API and no client code should ever use it. If you reference _vara in your code and it is in someone elses module you don't understand YOU ARE NOT SUPPOSED TO DO THAT! 1) This is an implemantation detail of this module, It is the users of my module who have to be extra carefull using it. Users of your module should NEVER KNOW any of the _ or __ stuff exists to begin with. 2) This is an implemantation detail of the other module, I should be extra carefull using it. You should NEVER use it. And I find variable starting or ending with an underscore ugly. :-) -- Antoon Pardon But like my previous post states, you can mark stuff private in Java all you want, you can still access. Having the compiler or runtime enforce that just adds an extra step to turn that enforcement off. You can do the same thing, in C++. So WHY does a language need this enforcement. And the large code base needs the robustness is not a valid argument. Since Apple has proven this NOT to be the case with Cocoa which is in Objective-C and knows about access control but doesn't really use them Anyone that things a language HAS to have these constructs enforced by the compiler or runtime, lacks disipline. Python has exactly what every other language EFFECTIVELY has, a common way to document or tag what is _private but might need Friend access, and what is REALLY __private. If you don't like this, then that is your problem go use a language that gives you that false sense of secuirty, don't expect it to change. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
danielx wrote:
Bruno Desthuilliers wrote:
danielx wrote:
(snip)
which gets me thinking again about
the stuff I self-censored. Since the dot syntax does something special
and unexpected in my case,
unexpected ? Did you ever wondered how the instance or class was
passed as first arg when doing method calls ?
Not knowing what's going on during method calls is exactly what
motivated me to post.
!-)
Ok, so now you have to read about descriptors, __getattribute__ and
__setattr__.
why not use some more dot-magic to implement
privates?
What for ? What makes you think we need language-inforced access
restriction ?
I knew someone would bring this up.
Indeed.
The motivation would not be to
provide restriction, but to help maintain clean api's. If you intended
for users to use only a subset of the methods in your class, why not
help them learn your api by presenting the stuff they can use not along
side the stuff they should not?
Obviously, such things would be omitted from your docs, but users also
learn by interacting with Python, which is really one of Python's great
virtues. When supporting documents aren't sufficient to learn an api
(I'm sure this never happens, so just humor me), you can always turn to
interactive Python.
...and source code...
This is exactly what it's there for. If nothing is
hidden, a user could be easily mislead to believe he can use a method
when he really shouldn't.
Single leading underscore means implementation, don't touch or you're
on your own.
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
--
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Re: function v. method
Bruno Desthuilliers wrote:
danielx wrote:
Bruno Desthuilliers wrote:
danielx wrote:
(snip)
which gets me thinking again about
the stuff I self-censored. Since the dot syntax does something special
and unexpected in my case,
unexpected ? Did you ever wondered how the instance or class was
passed as first arg when doing method calls ?
Not knowing what's going on during method calls is exactly what
motivated me to post.
!-)
Ok, so now you have to read about descriptors, __getattribute__ and
__setattr__.
why not use some more dot-magic to implement
privates?
What for ? What makes you think we need language-inforced access
restriction ?
I knew someone would bring this up.
Indeed.
The motivation would not be to
provide restriction, but to help maintain clean api's. If you intended
for users to use only a subset of the methods in your class, why not
help them learn your api by presenting the stuff they can use not along
side the stuff they should not?
Obviously, such things would be omitted from your docs, but users also
learn by interacting with Python, which is really one of Python's great
virtues. When supporting documents aren't sufficient to learn an api
(I'm sure this never happens, so just humor me), you can always turn to
interactive Python.
...and source code...
*shudders* What happened to all the goodness of abstraction?
This is exactly what it's there for. If nothing is
hidden, a user could be easily mislead to believe he can use a method
when he really shouldn't.
Single leading underscore means implementation, don't touch or you're
on your own.
I'll remember that. I had forgotten what the convention was for
labeling things do not touch.
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
--
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Re: function v. method
danielx wrote: Bruno Desthuilliers wrote: danielx wrote: At first I was going to post the following: !-- beginning of my original post -- (snip) !-- end of my original post, with ending censored -- but then I tried this: res = Foo.__dict__['func'] res is dan True And it all started to make sense. The surprising thing turned out to be not so surprising: When the expression Foo.func gets evaluated, we get a method which is just a wrapper around dan. Therefore, f is not dan! This is still a little bit of magic, FWIW, the function class implements the descriptor protocol... Here's the magic. which gets me thinking again about the stuff I self-censored. Since the dot syntax does something special and unexpected in my case, unexpected ? Did you ever wondered how the instance or class was passed as first arg when doing method calls ? Not knowing what's going on during method calls is exactly what motivated me to post. why not use some more dot-magic to implement privates? What for ? What makes you think we need language-inforced access restriction ? I knew someone would bring this up. The motivation would not be to provide restriction, but to help maintain clean api's. If you intended for users to use only a subset of the methods in your class, why not help them learn your api by presenting the stuff they can use not along side the stuff they should not? Obviously, such things would be omitted from your docs, but users also learn by interacting with Python, which is really one of Python's great virtues. When supporting documents aren't sufficient to learn an api (I'm sure this never happens, so just humor me), you can always turn to interactive Python. This is exactly what it's there for. If nothing is hidden, a user could be easily mislead to believe he can use a method when he really shouldn't. if you prefix with a single underscore, that tells the user, DON'T MESS WITH ME FROM OUTSIDE! I AM AN IMPLEMENTATION DETAIL! and it gets ommited from all the doc generation if you prefix with a double underscore, then they have to go even FARTHER out of their way to shoot themselves in the foot. Python takes the stance of personal responsiblity when it comes to access control. Which in NO WAY dimishes its robustness or anything else. just read the DailyWTF.com, incompentent people will abuse any language features in any language, and will figure out how to break programatic access control no matter how it is implemented. Matter of fact, Java which in another thread someone was ADAMANT that did not expose private anything from reflection ( and was wrong ) specifically allows you to access all the private members, functions, everything. You just need to tell it to turn all the safeties off. From the api: public void setAccessible(boolean flag) throws SecurityException Set the accessible flag for this object to the indicated boolean value. A value of true indicates that the reflected object should suppress Java language access checking when it is used. A value of false indicates that the reflected object should enforce Java language access checks. Setting the accessible flag in a reflected object permits sophisticated applications with sufficient privilege, such as Java Object Serialization or other persistence mechanisms, to manipulate objects in a manner that would normally be prohibited. so anything added to Python to enforce access control would immediately be forced to provide some means to over-ride the checks for pickle and the like. Not to even mention the argument that it would break crap loads of existing code base. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
danielx [EMAIL PROTECTED] wrote: ...and source code... *shudders* What happened to all the goodness of abstraction? http://www.joelonsoftware.com/articles/LeakyAbstractions.htm Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
Bruno Desthuilliers wrote:
danielx wrote:
At first I was going to post the following:
!-- beginning of my original post --
(snip)
!-- end of my original post, with ending censored --
but then I tried this:
res = Foo.__dict__['func']
res is dan
True
And it all started to make sense. The surprising thing turned out to be
not so surprising: When the expression Foo.func gets evaluated, we get
a method which is just a wrapper around dan. Therefore, f is not dan!
This is still a little bit of magic,
FWIW, the function class implements the descriptor protocol... Here's
the magic.
which gets me thinking again about
the stuff I self-censored. Since the dot syntax does something special
and unexpected in my case,
unexpected ? Did you ever wondered how the instance or class was
passed as first arg when doing method calls ?
Not knowing what's going on during method calls is exactly what
motivated me to post.
why not use some more dot-magic to implement
privates?
What for ? What makes you think we need language-inforced access
restriction ?
I knew someone would bring this up. The motivation would not be to
provide restriction, but to help maintain clean api's. If you intended
for users to use only a subset of the methods in your class, why not
help them learn your api by presenting the stuff they can use not along
side the stuff they should not?
Obviously, such things would be omitted from your docs, but users also
learn by interacting with Python, which is really one of Python's great
virtues. When supporting documents aren't sufficient to learn an api
(I'm sure this never happens, so just humor me), you can always turn to
interactive Python. This is exactly what it's there for. If nothing is
hidden, a user could be easily mislead to believe he can use a method
when he really shouldn't.
(snip)
BTW, I am aware of Python's name mangling feature.
Name mangling is mainly here to protect from accidental overridding. The
convention for implementation attributes is single-leading-underscore.
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
--
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Re: function v. method
Leif K-Brooks wrote: danielx wrote: This is still a little bit of magic, which gets me thinking again about the stuff I self-censored. Since the dot syntax does something special and unexpected in my case, why not use some more dot-magic to implement privates? Privates don't have to be entirely absent from Klass.__dict__ (which would make Python not introspective); they can just be invisible when using the dot-syntax. You can do this now, kind of: class Foo(object): ... x = property() ... def doStuffWithX(self): ... self.__dict__['x'] = 123 ... print self.__dict__['x'] ... bar = Foo() bar.doStuffWithX() 123 bar.x Traceback (most recent call last): File stdin, line 1, in ? AttributeError: unreadable attribute If you're proposing that self.x and bar.x should give different results, then that's quite a bit more magic than property() and methods use. They Yes, I had not considered that very carefully... both use the descriptor API; for more information on that, read http://python.org/download/releases/2.2.3/descrintro/. Let me finish reading that before I get back to your point. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
Duncan Booth wrote: danielx wrote: Foo.func = dan# -- Appearantly, something magical happens here, because... Foo.func unbound method Foo.dan f = Foo.func f is dan # -- things begins to look suprising here. False ismethod(f) True Imagine my surprise. Why would Python do this? Nothing magical happens at the point you said. The assignment is just an assignment and you saw that the function was stored unchanged when you looked in the class's dictionary. The magic happens when you access a member of a class or an instance. If the value is a descriptor then its __get__ method is called. Roughly speaking, Foo.func is equivalent to: Foo.__dict__['func'].__get__(None, Foo) unbound method Foo.dan Python does this so that it can support other descriptor types such as property, classmethod, staticmethod. You can see this happening if you define your own descriptor: class MyDesc(object): def __get__(self, *args): print __get__ called, args return None d = MyDesc() Foo.oops = d Foo.oops __get__ called (None, class __main__.Foo at 0x00B3F930) http://docs.python.org/ref/descriptor-invocation.html has a description of this. Although it claims Note that descriptors are only invoked for new style objects or classes (ones that subclass object() or type()). the descriptor mechanism is partially implemented for old style classes. Several aspects of descriptors don't work properly though in old-style classes which is one reason why you should always use new-style classes. Privates don't have to be entirely absent from Klass.__dict__ (which would make Python not introspective); they can just be invisible when using the dot-syntax. You could implement that using a data descriptor, but if you are going to prevent access to your private variables using the dot operator, then your code is going to look pretty silly with a lot of references to self.__dict__['theprivate'] which doesn't gain anything in readability over self.__theprivate. I believe you are talking about the same thing as Leif, but I can't quite tell. I'll need to read your paper as well :P. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
I guess the python devs are not interested in implementing something that would require new syntax and does not give something entirely new to the language. The good thing about python is, that the devs are only implementing ideas that are very cool. There are a lot of cool (!= very cool) ideas in rejected peps - but they were never implemented for good reasons. If you *really* need privates, just use the naming convention. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
danielx wrote: This is still a little bit of magic, which gets me thinking again about the stuff I self-censored. Since the dot syntax does something special and unexpected in my case, why not use some more dot-magic to implement privates? Privates don't have to be entirely absent from Klass.__dict__ (which would make Python not introspective); they can just be invisible when using the dot-syntax. You can do this now, kind of: class Foo(object): ... x = property() ... def doStuffWithX(self): ... self.__dict__['x'] = 123 ... print self.__dict__['x'] ... bar = Foo() bar.doStuffWithX() 123 bar.x Traceback (most recent call last): File stdin, line 1, in ? AttributeError: unreadable attribute If you're proposing that self.x and bar.x should give different results, then that's quite a bit more magic than property() and methods use. They both use the descriptor API; for more information on that, read http://python.org/download/releases/2.2.3/descrintro/. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
danielx wrote: Foo.func = dan# -- Appearantly, something magical happens here, because... Foo.func unbound method Foo.dan f = Foo.func f is dan # -- things begins to look suprising here. False ismethod(f) True Imagine my surprise. Why would Python do this? Nothing magical happens at the point you said. The assignment is just an assignment and you saw that the function was stored unchanged when you looked in the class's dictionary. The magic happens when you access a member of a class or an instance. If the value is a descriptor then its __get__ method is called. Roughly speaking, Foo.func is equivalent to: Foo.__dict__['func'].__get__(None, Foo) unbound method Foo.dan Python does this so that it can support other descriptor types such as property, classmethod, staticmethod. You can see this happening if you define your own descriptor: class MyDesc(object): def __get__(self, *args): print __get__ called, args return None d = MyDesc() Foo.oops = d Foo.oops __get__ called (None, class __main__.Foo at 0x00B3F930) http://docs.python.org/ref/descriptor-invocation.html has a description of this. Although it claims Note that descriptors are only invoked for new style objects or classes (ones that subclass object() or type()). the descriptor mechanism is partially implemented for old style classes. Several aspects of descriptors don't work properly though in old-style classes which is one reason why you should always use new-style classes. Privates don't have to be entirely absent from Klass.__dict__ (which would make Python not introspective); they can just be invisible when using the dot-syntax. You could implement that using a data descriptor, but if you are going to prevent access to your private variables using the dot operator, then your code is going to look pretty silly with a lot of references to self.__dict__['theprivate'] which doesn't gain anything in readability over self.__theprivate. -- http://mail.python.org/mailman/listinfo/python-list
Re: function v. method
danielx wrote:
At first I was going to post the following:
!-- beginning of my original post --
(snip)
!-- end of my original post, with ending censored --
but then I tried this:
res = Foo.__dict__['func']
res is dan
True
And it all started to make sense. The surprising thing turned out to be
not so surprising: When the expression Foo.func gets evaluated, we get
a method which is just a wrapper around dan. Therefore, f is not dan!
This is still a little bit of magic,
FWIW, the function class implements the descriptor protocol... Here's
the magic.
which gets me thinking again about
the stuff I self-censored. Since the dot syntax does something special
and unexpected in my case,
unexpected ? Did you ever wondered how the instance or class was
passed as first arg when doing method calls ?
why not use some more dot-magic to implement
privates?
What for ? What makes you think we need language-inforced access
restriction ?
(snip)
BTW, I am aware of Python's name mangling feature.
Name mangling is mainly here to protect from accidental overridding. The
convention for implementation attributes is single-leading-underscore.
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
--
http://mail.python.org/mailman/listinfo/python-list
function v. method
At first I was going to post the following: !-- beginning of my original post -- I just discovered the inspect module, which contains the isfunction and ismethod functions. For some reason, I used to be under the impression that Python methods are no different from Python functions. Naturally, I wondered why both of these needed to exist (I also later discovered the isroutine function). So I started to experiment at prompt. Here's what I did: from inspect import * def dan(): pass ... ismethod(dan) False isfunction(dan) True class Foo: ... def meth(self): pass ... m = Foo.meth m unbound method Foo.meth ismethod(m) True Foo.func = dan# -- Appearantly, something magical happens here, because... Foo.func unbound method Foo.dan f = Foo.func f is dan # -- things begins to look suprising here. False ismethod(f) True Imagine my surprise. Why would Python do this? !-- end of my original post, with ending censored -- but then I tried this: res = Foo.__dict__['func'] res is dan True And it all started to make sense. The surprising thing turned out to be not so surprising: When the expression Foo.func gets evaluated, we get a method which is just a wrapper around dan. Therefore, f is not dan! This is still a little bit of magic, which gets me thinking again about the stuff I self-censored. Since the dot syntax does something special and unexpected in my case, why not use some more dot-magic to implement privates? Privates don't have to be entirely absent from Klass.__dict__ (which would make Python not introspective); they can just be invisible when using the dot-syntax. BTW, I am aware of Python's name mangling feature. -- http://mail.python.org/mailman/listinfo/python-list
