Attack a sacred Python Cow
Jordan
I'm a big Python fan who used to be involved semi regularly in
comp.lang.python (lots of lurking, occasional posting) but kind of
trailed off a bit. I just wrote a frustration inspired rant on my
blog, and I thought it was relevant enough as a wider issue to the
Python community to post here for your discussion and consideration.
This is not flamebait. I love Python, and I'm not out to antagonise
the community. I also realise that one of the issues I raise is way
too ingrained to be changed now. I'd just like to share my thinking on
a misstep in Python's guiding principles that has done more harm than
good IMO. So anyway, here's the post.
I've become utterly convinced that at least one criticism leveled at
my favourite overall programming language, Python, is utterly true and
fair. After quite a while away from writing Python code, I started
last night on a whim to knock up some code for a prototype of an idea
I once had. It's going swimmingly; the Python Image Library, which I'd
never used before, seems quick, intuitive, and with the all the
features I need for this project. As for Python itself, well, my heart
still belongs to whitespace delimitation. All the basics of Python
coding are there in my mind like I never stopped using them, or like
I've been programming in this language for 10 years.
Except when it comes to Classes. I added some classes to code that had
previously just been functions, and you know what I did - or rather,
forgot to do? Put in the 'self'. In front of some of the variable
accesses, but more noticably, at the start of *every single method
argument list.* This cannot be any longer blamed as a hangover from
Java - I've written a ton more code, more recently in Python than in
Java or any other OO language. What's more, every time I go back to
Python after a break of more than about a week or so, I start making
this 'mistake' again. The perennial justification for this 'feature'
of the language? That old Python favourite, "Explicit is better than
implicit."
I'm sorry, but EXPLICIT IS NOT NECESSARILY BETTER THAN IMPLICIT.
Assembler is explicit FFS. Intuitive, clever, dependable, expected,
well-designed *implicit* behaviour is one of the chief reasons why I
use a high level language. Implicitly garbage collect old objects for
me? Yes, please!
I was once bitten by a Python wart I felt was bad enough to raise and
spend some effort advocating change for on comp.lang.python (never got
around to doing a PEP; partly laziness, partly young and inexperienced
enough to be intimidated at the thought. Still am, perhaps.)
The following doesn't work as any sane, reasonable person would
expect:
# Blog code, not tested
class A():
def __eq__(self, obj):
return True
a = A()
b = []
assert a == b
assert not (a != b)
The second assertion fails. Why? Because coding __eq__, the most
obvious way to make a class have equality based comparisons, buys you
nothing from the != operator. != isn't (by default) a synonym for the
negation of == (unlike in, say, every other language ever); not only
will Python let you make them mean different things, without
documenting this fact - it actively encourages you to do so.
There were a disturbingly high number of people defending this
(including one quite renowned Pythonista, think it might have been
Effbot). Some had the temerity to fall back on "Explicit is better
than implict: if you want != to work, you should damn well code
__ne__!"
Why, for heaven's sake, should I have to, when in 99.99% of use cases
(and of those 0.01% instances quoted in the argument at the time only
one struck me as remotely compelling) every programmer is going to
want __ne__ to be the logical negation of __eq__? Why, dear Python,
are you making me write evil Java-style language power reducing
boilerplate to do the thing you should be doing yourself anyway?
What's more, every programmer is going to unconciously expect it to
work this way, and be as utterly as mystified as me when it fails to
do so. Don't tell me to RTFM and don't tell me to be explicit. I'll
repeat myself - if I wanted to be explicit, I'd be using C and
managing my own memory thank you very much. Better yet, I'd explicitly
and graphically swear - swear in frustration at this entrenched design
philosophy madness that afflicts my favourite language.
I think the real problem with the explicit is better than implicit,
though, is that while you can see the underlying truth its trying to
get at (which is perhaps better expressed by Ruby's more equivocal,
less dependable, but more useful Principle of Least Surprise), in its
stated form its actually kind of meanginless and is used mainly in
defence of warts - no, we'll call them for what they are, a language
design *bugs*.
You see, the problem is, there's no such thing of explict in
programming. Its not a question of not doing things implicitly; its a
question of doing the most sensible thing implicitly. For example this
python code:
some_obj.some_meth(some_arg1, some_arg2)
is implicitly equivalent to
SomeClass.some_meth(some_obj, some_arg1, some_arg2)
which in turn gives us self as a reference to some_obj, and Python's
OO model merrily pretends its the same as Java's when in fact is a
smarter version that just superficially looks the same.
The problem is that the explicit requirement to have self at the start
of every method is something that should be shipped off to the
implicit category. You should have to be explicit, yes - explicit when
you want the *other* behaviour, of self *not* being an argument,
because thats the more unusual, less likely case.
Likewise,
a != b
is implicitly equivalent to something like calling this function (may
not be correct, its a while since I was heavily involved in this
issue):
def equal(a, b):
if hasattr(a, "__ne__"): return a.__ne__(b)
if hasattr(b, "__ne__"): return b.__ne__(a)
if hasattr(a, "__cmp__"): return not (a.__cmp__(b) == 0)
if hasattr(b, "__cmp__"): return not (b.__cmp__(a) == 0)
return not (a is b)
There's absolutely nothing explicit about this. I wasn't arguing for
making behaviour implicit; I was arguing for changing the stupid
implict behaviour to something more sensible and less surprising.
The sad thing is there are plenty of smart Python programmers who will
justify all kinds of idiocy in the name of their holy crusade against
the implict.
If there was one change I could make to Python, it would be to get
that damn line out of the Zen.
Jordan
P.S. Forgive the typos, it was blogged in extreme haste and then only
quickly proofread and edited before posting here. Hopefully the point
I'm making is not diminshed by your reduced respect for me as a result
of my carelessness :-)
pluskid
> Hi everyone,
>
> I'm a big Python fan who used to be involved semi regularly in
> comp.lang.python (lots of lurking, occasional posting) but kind of
> trailed off a bit. I just wrote a frustration inspired rant on my
> blog, and I thought it was relevant enough as a wider issue to the
> Python community to post here for your discussion and consideration.
>
+1 for most of your opinion. I was also bitten by the __eq__/__ne__
problem this morning. :)
Fredrik Lundh
> Except when it comes to Classes. I added some classes to code that had
> previously just been functions, and you know what I did - or rather,
> forgot to do? Put in the 'self'. In front of some of the variable
> accesses, but more noticably, at the start of *every single method
> argument list.* This cannot be any longer blamed as a hangover from
> Java - I've written a ton more code, more recently in Python than in
> Java or any other OO language. What's more, every time I go back to
> Python after a break of more than about a week or so, I start making
> this 'mistake' again. The perennial justification for this 'feature'
> of the language? That old Python favourite, "Explicit is better than
> implicit."
Do you seriously think that Python is designed by mindless application
of a set of humorous and somewhat self-deprecating observations posted
to a newsgroup a number of years ago?
</F>
Jordan
I just think Explicit is better than Implicit is taken seriously by a
large segment the Python community as a guiding principle, and overall
its influence does more harm than good.
Clearly self being in every argument list was a decision arrived at
long before the Zen was ever coined. Its merely an example of what I
feel is a shortcoming in the conventional 'pythonic' approach to
thinking about problems.
The reluctance to admit that the __eq__ behaviour is a poor design
choice is further evidence; its something (unlike self) that quite
conceivably could be changed, and should be changed, but its somehow
seen (by certain people) as the way that Python should do things.
Bruno Desthuilliers
(snip rant about self and __eq__ / __ne__)
1/ about the __eq__ / __ne__ stuff:
Please get your facts, the behaviour *is* actually fully documented:
"""
There are no implied relationships among the comparison operators. The
truth of x==y does not imply that x!=y is false. Accordingly, when
defining __eq__(), one should also define __ne__() so that the operators
will behave as expected.
"""
http://docs.python.org/ref/customization.html
FWIW, the __lt__ / __le__ / __eq__ / __ne__ / __gt__ / __ge__ methods
set, known as "rich comparisons", was added in Python 2.1 to give more
fine-grained control on comparisons. If you don't need such a
granularity, just implement the __cmp__ method and you'll have all
comparison operators working as expected.
2/ wrt/ self in functions signatures:
How would you handle this case with an implicit 'self' :
class Foo(object):
pass
def bar(self):
print self
Foo.bar = bar
Torsten Bronger
Bruno Desthuilliers writes:
> [...]
>
> How would you handle this case with an implicit 'self' :
>
> class Foo(object):
> pass
>
> def bar(self):
> print self
>
> Foo.bar = bar
Just like this. However, the compiler could add "self" to
non-decorated methods which are defined within "class".
Tschö,
Torsten.
--
Torsten Bronger, aquisgrana, europa vetus
Jabber ID: torsten...@jabber.rwth-aachen.de
Jordan
wrote:
Yeah, forgot what I said, Torsten's reply is much better :-)
Lawrence D'Oliveiro
<52404933-ce08-4dc1...@r35g2000prm.googlegroups.com>, Jordan
wrote:
> Except when it comes to Classes. I added some classes to code that had
> previously just been functions, and you know what I did - or rather,
> forgot to do? Put in the 'self'. In front of some of the variable
> accesses, but more noticably, at the start of *every single method
> argument list.*
The reason is quite simple. Python is not truly an "object-oriented"
language. It's sufficiently close to fool those accustomed to OO ways of
doing things, but it doesn't force you to do things that way. You still
have the choice. An implicit "self" would take away that choice.
Sebastian "lunar" Wiesner
> # Blog code, not tested
> class A():
> def __eq__(self, obj):
> return True
> a = A()
> b = []
> assert a == b
> assert not (a != b)
>
> The second assertion fails. Why? Because coding __eq__, the most
> obvious way to make a class have equality based comparisons, buys you
> nothing from the != operator. != isn't (by default) a synonym for the
> negation of == (unlike in, say, every other language ever);
This is just plain wrong for at least C# and C++. C# wants you to
explicitly overload "!=", if you have overloaded "==", C++ complains
about "!=" not being defined for class A. If you had derived A from a
another class in C++, the compiler would happily use the operator from the
base class instead of doing silly aliasing of "!=" to "! ==" ...
> The sad thing is there are plenty of smart Python programmers who will
> justify all kinds of idiocy in the name of their holy crusade against
> the implict.
>
> If there was one change I could make to Python, it would be to get
> that damn line out of the Zen.
Fortunately, Python isn't designed according to your ideas, and won't
change, so consider your posting a waste of time. If feeling like bringing
such old "issues" up again next time, spend your time learning another
programming language, as you would obviously not get happy with Python
anyway ...
--
Freedom is always the freedom of dissenters.
(Rosa Luxemburg)
Jordan
(apologies therefore if a paraphrased "quantum duplicate" of this
message is eventually forthcoming.)
Torsten has adequately responded to his second point, so I need only
replicated what I said for the first.
> Please get your facts, the behaviour *is* actually fully documented:
I have the facts. I know full well the behaviour is documented - it
was pointed out at the time of the original discussion. Documenting a
confusing, unintuitive design decision (whether its in a programming
language, an end user GUI app or anything in between) doesn't justify
it.
To attack a strawman: "foolanguage uses the bar IO library; printing
to stdout takes about 10 mins on the average machine. But thats ok,
because look, its documented right here."
> FWIW, the __lt__ / __le__ / __eq__ / __ne__ / __gt__ / __ge__ methods
> set, known as "rich comparisons", was added in Python 2.1 to give more
> fine-grained control on comparisons. If you don't need such a
> granularity, just implement the __cmp__ method and you'll have all
> comparison operators working as expected.
First, the most serious justification for rich comparisons I remember
seeing was that scipy "needed" them. I never saw a good reason scipy
couldnt use methods like the rest of us mortals, nor why it was
justifiable introducing a wart into the entire language for the sake
of mildly conveniencing an (admittedly important and widely used)
library.
Second, fine, have silly C++-operator-overloading-style rich
comparisons that confuse people reading your code if you must. Why
does it have to be the default behaviour? Its people wanting __ne__ do
do something other than not __eq__ who should have to be explicit
about it.
Third, __cmp__ is no good as a fix. Most classes that wan't equality
comparison (== and !=) don't want ordered based comparison (>= etc.)
thrown in as well. I shouldn't implement __cmp__ unless I want my
class to implement every order comparison operator.
Fourth, I'm trying to examine the wider implications of the Explicit >
Implict mantra here, not resurrect an old campaign to change !=
behaviour that I think is probably a lost cause (if it happens as a
side effect though, that'd be kinda cool.)
Jordan
> This is just plain wrong for at least C# and C++. C# wants you to
> explicitly overload "!=", if you have overloaded "==",
While this is as inconvenient as Python at least it doesn't catch you
unawares. C# 1 (or maybe 0.5), Python 0.
> C++ complains
> about "!=" not being defined for class A.
See above. C++ 1, Python 0.
So in showing my clearly hyperbolic comment was technically incorrect
(something I could have told you myself), you have merely shown that
two languages I find vastly inferior to Python overall are actually
better than it in this case.
> Fortunately, Python isn't designed according to your ideas, and won't
> change, so consider your posting a waste of time. If feeling like bringing
> such old "issues" up again next time, spend your time learning another
> programming language, as you would obviously not get happy with Python
> anyway ...
OK, if that's your response, that's sad. Of course, I try to learn new
languages all the time. Python is still IMO the best. If the attitude
in the community in response to feedback/criticism has gone from
"maybe you've got a point" to "your a lunatic, we'll never change",
well, only Python will suffer in the long term.
Jordan
central.gen.new_zealand> wrote:
> In message
> <52404933-ce08-4dc1-a558-935bbbae7...@r35g2000prm.googlegroups.com>, Jordan
You could still explicitly request non-implicit self on a method by
method basis.
Kay Schluehr
wrote:
> Hallöchen!
>
> Bruno Desthuilliers writes:
> > [...]
>
> > How would you handle this case with an implicit 'self' :
>
> > class Foo(object):
> > pass
>
> > def bar(self):
> > print self
>
> > Foo.bar = bar
>
> Just like this. However, the compiler could add "self" to
> non-decorated methods which are defined within "class".
And $self2, $self3, ... to the object methods of nested classes and
$cls2, $cls3, ... to the classmethods of those classes...?
And when we are at it, here is a nice little exercise for the
proponents of compiler magic.
Write a decorator that takes and returns a method and prints the
object the method is bound to. It's very easy to do it when the object
is passed explicitely:
def print_self(func):
def call(self, *args, **kwd):
print self
return func(self, *args, **kwd)
return call
Conceptual clarity isn't always an entirely bad thing to have.
Torsten Bronger
Kay Schluehr writes:
> On 24 Jul., 11:40, Torsten Bronger <bron...@physik.rwth-aachen.de>
> wrote:
>>
>> Bruno Desthuilliers writes:
>>
>>> [...]
>>>
>>> How would you handle this case with an implicit 'self' :
>>>
>>> class Foo(object):
>>> pass
>>>
>>> def bar(self):
>>> print self
>>>
>>> Foo.bar = bar
>>
>> Just like this. However, the compiler could add "self" to
>> non-decorated methods which are defined within "class".
>
> And $self2, $self3, ... to the object methods of nested classes
> and $cls2, $cls3, ... to the classmethods of those classes...?
One could surely find ways to realise this. However, the design
goal should be: Make the frequent case simple, and the rare case
possible.
(Actually, I'm -0 on this anyway because I forget "self" very
seldomly, and you would still have ".self" all over the place.)
alex23
> If the attitude
> in the community in response to feedback/criticism has gone from
> "maybe you've got a point" to "your a lunatic, we'll never change",
> well, only Python will suffer in the long term.
Personally, I think it has more to do with statements like "there are
plenty of smart Python programmers who will
justify all kinds of idiocy in the name of their holy crusade" than
with your position. You don't begin a discussion by discrediting
anyone who might disagree with you as some kind of religious bigot
while simultaneously holding that you are the only sane voice
speaking.
Sebastian "lunar" Wiesner
>> Fortunately, Python isn't designed according to your ideas, and won't
>> change, so consider your posting a waste of time. If feeling like
>> bringing such old "issues" up again next time, spend your time learning
>> another programming language, as you would obviously not get happy with
>> Python anyway ...
>
> OK, if that's your response, that's sad. Of course, I try to learn new
> languages all the time. Python is still IMO the best. If the attitude
> in the community in response to feedback/criticism has gone from
> "maybe you've got a point" to "your a lunatic, we'll never change",
> well, only Python will suffer in the long term.
I don't really mind, what you think about my response. Python will suffer
from it as little as it will suffer from your complaints: These things
will not change, whatever any of us says about them. So this discussion
unlikely to produce any new insight, especially because this as been
discussed over and over again in the past, without any effect on Python.
Let's just drop this, and if you want to complain next time, just complain
about something, that is really worth being complained about, like for
instance old and outdated modules in the standard library, or real
showstoppers in Python (e.g. the GIL).
Jordan
> plenty of smart Python programmers who will
> justify all kinds of idiocy in the name of their holy crusade" than
> with your position. You don't begin a discussion by discrediting
> anyone who might disagree with you as some kind of religious bigot
> while simultaneously holding that you are the only sane voice
> speaking.
I didn't set out to discredit anyone who might disagree with me; in
fact I didn't in anyway try to pre-empt any person who might disagree
with my thesis. I merely stated an observation - I have in the past
seen seemingly intelligent people take silly stands in the name of
Explicit is greater than Implicit (not just on comp.lang.python, and
not just concerning != or self).
I wish in retrospect I'd had the time, patience and focus to edit the
initial post to make it more measured and less inflammatory, because
its clear the tone detracts from the argument I'm making, which I feel
still stands.
So if you wish, ignore the specifics of the frustration that inspired
me and consider only the thrust of what I'm saying:
"Explicit is better than Implict" considered harmful. Discuss.
Ben Finney
> I just think Explicit is better than Implicit is taken seriously by
> a large segment the Python community as a guiding principle
Indeed it is. However, it has to compete with all the other principles
in the Zen of Python, which have equal status.
> and overall its influence does more harm than good.
Thanks for your opinion. I disagree strongly: I think its influence is
nicely balanced by the other important principles that are also
followed.
--
\ “The way to build large Python applications is to componentize |
`\ and loosely-couple the hell out of everything.” —Aahz |
_o__) |
Ben Finney
Ben Finney
> If the attitude in the community in response to feedback/criticism
> has gone from "maybe you've got a point" to "your a lunatic, we'll
> never change", well, only Python will suffer in the long term.
You're not a lunatic.
We, and Python itself, change quite readily.
Neither of those mean your ideas in this instance have merit.
--
\ “Pinky, are you pondering what I'm pondering?” “Well, I think |
`\ so, Brain, but do I really need two tongues?” —_Pinky and The |
_o__) Brain_ |
Ben Finney
Jordan
> from it as little as it will suffer from your complaints: These things
> will not change, whatever any of us says about them. So this discussion
> unlikely to produce any new insight, especially because this as been
> discussed over and over again in the past, without any effect on Python.
You're right, of course. Because Python is in so many ways what I'm
looking for in a language, I transform it in my mind to my own,
personal ideal, close to the real existing language but with what I
consider to be the imperfections removed.
I'm not suggesting getting rid of explicit self, even in "Python
4000." Not because of the advantages it gives, which are some but
don't outweigh the net loss in my ledger. It just wouldn't be
Pythonic. I know its not a Pythonic thing to want. Thats my problem -
because I have a largely Pythonic approach in some areas, it upsets me
when there's a mismatch. So lets say I'm -1 for introducing it into a
language and +0 for keeping it in Python now that its entrenched.
If a lot of users keep bringing up something like this, well my
attitude used to be the same as yours - "learn to love Python for what
it is." Maybe
> Let's just drop this, and if you want to complain next time, just complain
> about something, that is really worth being complained about, like for
> instance old and outdated modules in the standard library, or real
> showstoppers in Python (e.g. the GIL).
Its worth complaining about because I'm not just someone who has
stumbled across Python after years of Java and PHP, and hasn't really
grokked it, and has jumped on the net at once to start a flamewar. I'm
someone who loves Python, uses it in preference to other languages,
and have now returned to it after a bit of a break and its finally hit
me over the head like a tonne of bricks "Hey, I can see exactly what
all those internet trolls were talking about. This *is* a really
annoying and silly state of affairs."
I was trying not to change explicit self, or even != (which has a much
better case.) I was trying to ask the community to reconsider a
premise that the language is built around. Explicit is actually kinda
annoying a lot of the time, viz., java. This is about social and
philosophical adjustments, not technical ones.
In reality? I'll just keep writing Python (hopefully enough so that
explicit self become burned into muscle memory), and use other
languages when necessary (no more C than I have to, looking forward to
dabbling in Erlang soon, and one day overcoming the parentheses phobia
enough to really tackle Lisp properly). When I'm old enough and wise
enough, and have the time, energy and inclination, maybe I'll sit down
and put a proper effort into designing and implementing a new language
that bests suits my own particular style and needs. Just maybe it'll
be good enough that smart people will rally to defend its design
principles from people attacking them on the internet :-)
Bruno Desthuilliers
> OK, it seems my original reply to Bruno got lost in the Aether
> (apologies therefore if a paraphrased "quantum duplicate" of this
> message is eventually forthcoming.)
>
> Torsten has adequately responded to his second point,
Not MHO, by far.
> so I need only
> replicated what I said for the first.
>
>> Please get your facts, the behaviour *is* actually fully documented:
>
> I have the facts. I know full well the behaviour is documented
Then why do you write, let me quote:
"""
(snip) coding __eq__ (snip) buys you
nothing from the != operator. != isn't (by default) a synonym for the
negation of == (unlike in, say, every other language ever); not only
will Python let you make them mean different things, without
documenting this fact - it actively encourages you to do so.
"""
>- it
> was pointed out at the time of the original discussion. Documenting a
> confusing, unintuitive design decision (whether its in a programming
> language, an end user GUI app or anything in between) doesn't justify
> it.
I was not commenting on the actual design choice, just stating that it
is actually documented.
> To attack a strawman: "foolanguage uses the bar IO library; printing
> to stdout takes about 10 mins on the average machine. But thats ok,
> because look, its documented right here."
And you're talking about strawman ??? Come on, you obviously can tell
the difference between a one-line statement and your above strawman
argument, don't you ?
Please understand that I'm not arguing about this particular design
choice (and FWIW, I'd mostly agree on the point that having a != b
different from not (a == b) is actually a wart). I'm just correcting
your statement about the behaviour of __eq__ / __ne__ not being
documented, which is obviously false.
(snip)
Bruno Desthuilliers
> Hallöchen!
>
> Bruno Desthuilliers writes:
>
>> [...]
>>
>> How would you handle this case with an implicit 'self' :
>>
>> class Foo(object):
>> pass
>>
>> def bar(self):
>> print self
>>
>> Foo.bar = bar
>
> Just like this. However, the compiler could add "self" to
> non-decorated methods which are defined within "class".
What's defined within classes are plain functions. It's actually the
lookup mechanism that wraps them into methods (and manage to insert the
current instance as first argument).
cokof...@gmail.com
> Please understand that I'm not arguing about this particular design
> choice (and FWIW, I'd mostly agree on the point that having a != b
> different from not (a == b) is actually a wart). I'm just correcting
> your statement about the behaviour of __eq__ / __ne__ not being
> documented, which is obviously false.
>
> (snip)
What was the reasoning behind having both __eq__ / __ne__ anyway? To
fit in with the equality comparisons? I do agree this one seems like
a wart, but not a serious one. I'd say it would make more sense for
the interpreter to provide a warning on classes that define one and
not that other, at least if set to a certain level, similar to -3 for
depreciated.
(Or does this exist? I think a "wart" catching level that outputs
potential warts and issues would be a useful addition!)
Jordan
>
> """
> (snip) coding __eq__ (snip) buys you
> nothing from the != operator. != isn't (by default) a synonym for the
> negation of == (unlike in, say, every other language ever); not only
> will Python let you make them mean different things, without
> documenting this fact - it actively encourages you to do so.
> """
My words aren't as clear as they should be. I mean that Python lets
*you* do something without documenting, or rather stating to use a
better term, that your intention is the non-obvious one. I'm not
saying that Python itself lacks documentation for its own behaviour;
I'm saying it should force you to make your intentions clear and
visible to someone reading your code when you want to do something non-
obvious.
> I was not commenting on the actual design choice, just stating that it
> is actually documented.
Yes, it is. I apologise for the poor construction of my statement
which led to this confusion.
> And you're talking about strawman ??? Come on, you obviously can tell
> the difference between a one-line statement and your above strawman
> argument, don't you ?
I'm talking about strawmen because I was deliberately choosing to
invoke one with rhetorical flourish for the purposes of making my
point forcefully. I wanted people to be clear that I knew perfectly
well what I was doing and that they needn't call me out on it.
> Please understand that I'm not arguing about this particular design
> choice (and FWIW, I'd mostly agree on the point that having a != b
> different from not (a == b) is actually a wart). I'm just correcting
> your statement about the behaviour of __eq__ / __ne__ not being
> documented, which is obviously false.
Good, at least we've come to a point in this discussion where I can
firmly agree with somebody.
Bruno Desthuilliers
> Hallöchen!
>
> Kay Schluehr writes:
>
>> On 24 Jul., 11:40, Torsten Bronger <bron...@physik.rwth-aachen.de>
>> wrote:
>>> Bruno Desthuilliers writes:
>>>
>>>> [...]
>>>>
>>>> How would you handle this case with an implicit 'self' :
>>>>
>>>> class Foo(object):
>>>> pass
>>>>
>>>> def bar(self):
>>>> print self
>>>>
>>>> Foo.bar = bar
>>> Just like this. However, the compiler could add "self" to
>>> non-decorated methods which are defined within "class".
>> And $self2, $self3, ... to the object methods of nested classes
>> and $cls2, $cls3, ... to the classmethods of those classes...?
>
> One could surely find ways to realise this. However, the design
> goal should be: Make the frequent case simple, and the rare case
> possible.
Given the (more and more prominent) use of decorators, metaclasses and
other meta-programming techniques in Python, I'm not sure the cases
where you really need access to Python's object model inners are that
"rare". Not in my code at least.
cokof...@gmail.com
> My words aren't as clear as they should be. I mean that Python lets
> *you* do something without documenting, or rather stating to use a
> better term, that your intention is the non-obvious one. I'm not
> saying that Python itself lacks documentation for its own behaviour;
> I'm saying it should force you to make your intentions clear and
> visible to someone reading your code when you want to do something non-
> obvious.
>
I take it you are relating to the need for less comments within the
code as the idea is the Python code itself is readable? Or are you
saying that when someone does a clever trick it should be documented
better? I'm a little confused as what you mean by no-documenting? I
always add doc-strings to modules I will be using heavily as well as a
README with them. But that isn't different from programming in other
languages and using comments.
(Do you mean something like JavaDoc?)
Ben Finney
> Explicit is actually kinda annoying a lot of the time
Yes. It is also very helpful for those who will later try to
understand, interface with, debug, modify, or otherwise work with the
code (including, in a great many cases, the original author of that
code).
The great boost that EIBTI grants to maintainability trumps, in my
view, the annoyance felt by some at the time of writing the code.
--
\ “An eye for an eye would make the whole world blind.” —Mahatma |
`\ Gandhi |
_o__) |
Ben Finney
Bruno Desthuilliers
> In message
> <52404933-ce08-4dc1...@r35g2000prm.googlegroups.com>, Jordan
> wrote:
>
>> Except when it comes to Classes. I added some classes to code that had
>> previously just been functions, and you know what I did - or rather,
>> forgot to do? Put in the 'self'. In front of some of the variable
>> accesses, but more noticably, at the start of *every single method
>> argument list.*
>
> The reason is quite simple. Python is not truly an "object-oriented"
> language.
Oh yes ? What's missing exactly ? You have objects that have an id,
state and behaviour, and you have a message-passing mechanism.
You meant "Python is not truly a mainstream class-based language", I think.
> It's sufficiently close to fool those accustomed to OO ways of
> doing things,
s/OO/class-based/
> but it doesn't force you to do things that way. You still
> have the choice. An implicit "self" would take away that choice.
It's not even a question of OO/non-OO. An implicit "self" would take
away some things that makes Python's *object* model so powerful.
Jordan
> You're not a lunatic.
>
> We, and Python itself, change quite readily.
>
> Neither of those mean your ideas in this instance have merit.
You're right, these premises don't lead to this conclusion. Neither do
they lead to its negation, of course.
As it happens, you're wrong on both counts. I do in fact suffer from a
mental illness and have spent a week in a psych ward, so am a lunatic
by some reasonable definitions. Python readily changes in some
regards, but not in others. Of course, a great many things of worth
have this as one of their essential qualities.
Pithy replies are fun.
> Thanks for your opinion. I disagree strongly: I think its influence is
> nicely balanced by the other important principles that are also
> followed.
This isn't just being clever, there's substance here. A clearly stated
opposing position, with a decent if somewhat short justification.
I think you're right insofar as you go - that if someone really sits
down, and thinks clearly about all the Pythonic principles, as a
whole, and in detail, then the net result in the shaping their
thinking will be positive more often than not.
Perhaps we're just looking at an instance of a wider problem - smart
people boil good ideas down into short slogans, which are nice and
memorable and somewhat helpful, but can lead to bad consequences when
lots of others start overusing or misunderstanding them.
Tim Golden
deliberate play on "flog a dead horse" or
merely an ironic one :)
TJG
Torsten Bronger
Bruno Desthuilliers writes:
> Torsten Bronger a écrit :
>
>> Kay Schluehr writes:
>>
>>> On 24 Jul., 11:40, Torsten Bronger <bron...@physik.rwth-aachen.de>
>>> wrote:
>>>
>>>> [...] Just like this. However, the compiler could add "self"
>>>> to non-decorated methods which are defined within "class".
>>>
>>> And $self2, $self3, ... to the object methods of nested classes
>>> and $cls2, $cls3, ... to the classmethods of those classes...?
>>
>> One could surely find ways to realise this. However, the design
>> goal should be: Make the frequent case simple, and the rare case
>> possible.
>
> Given the (more and more prominent) use of decorators, metaclasses
> and other meta-programming techniques in Python, I'm not sure the
> cases where you really need access to Python's object model inners
> are that "rare". Not in my code at least.
What does "not rare" mean for you?
Torsten Bronger
Bruno Desthuilliers writes:
> Torsten Bronger a écrit :
>
And why does this make the implicit insertion of "self" difficult?
I could easily write a preprocessor which does it after all.
Paul Boddie
<basti.wies...@gmx.net> wrote:
>
> Fortunately, Python isn't designed according to your ideas, and won't
> change, so consider your posting a waste of time.
This is the kind of petty response that serves only to shut down
discussion that might actually lead to genuine attempts to remedy
issues (or "warts") with Python. Although the tone of the complaint
was badly chosen, it is always worth jumping over the fence and
considering whether things could be made better. Without complaints
being aired, how do you expect any advances around things like the
"old and outdated modules in the standard library, or real
showstoppers in Python (e.g. the GIL)" that you mention elsewhere?
> If feeling like bringing such old "issues" up again next time, spend
> your time learning another programming language, as you would
> obviously not get happy with Python anyway ...
Such a constructive response that is! Instead, I think it is
interesting to consider why methods still require an explicit "self"
parameter - something which has been discussed previously - and
whether there might be a case for omitting it from the signature -
perhaps in a variant of Python - in methods which are defined within
class definitions (as opposed to those assigned to classes later).
Indeed, there's scope for experimentation with Python variants, just
to investigate whether certain features added to CPython can be
considered essential, and which features might be considered of
marginal benefit. I recall that some features (eg. lexical scoping and
closures) were eventually added to Python partly to remedy issues with
lambda definitions, but also because the lack of such features was
cited repeatedly by proponents of other languages. In such a climate,
it can be easier to "meet the challenge" and implement features to
silence the critics rather than to insist that they are of marginal
benefit (although it's interesting to note this in a thread where
improvement suggestions are deemed "a waste of time" - I suppose the
community is now more resistant to suggestions from "unofficial"
sources).
A review of such language "enhancement" decisions would be
interesting, but since one shouldn't expect this from the CPython
implementers, I feel that it is the role of others to do so in their
own experiments. Of course, such experiments are often derided as
"lesser Pythons" or misunderstood, but that's another unfortunate
trait exhibited by parts of the Python community.
Paul
Sebastian "lunar" Wiesner
> Hallöchen!
>
> Bruno Desthuilliers writes:
>
>> Torsten Bronger a écrit :
>>
>>> Bruno Desthuilliers writes:
>>>
>>>> [...]
>>>>
>>>> How would you handle this case with an implicit 'self' :
>>>>
>>>> class Foo(object):
>>>> pass
>>>>
>>>> def bar(self):
>>>> print self
>>>>
>>>> Foo.bar = bar
>>>
>>> Just like this. However, the compiler could add "self" to
>>> non-decorated methods which are defined within "class".
>>
>> What's defined within classes are plain functions. It's actually
>> the lookup mechanism that wraps them into methods (and manage to
>> insert the current instance as first argument).
>
> And why does this make the implicit insertion of "self" difficult?
> I could easily write a preprocessor which does it after all.
Who said, that it would be "difficult"? He just corrected your statement
about definitions inside a class, and did not make any assumption about
making "self" implicit.
I'd assume, that making self implicit wouldn't be that difficult to assume.
But does the fact, that it could easily be done, alone mean, that it
_should_ be done? The explicit "self" was a design decision, that can't
really be judged by technical arguments from implementation side. Its a
discussion about design from a programmers point of view ...
alex23
wrote:
> I could easily write a preprocessor which does it after all.
Have you considered actually doing so? That might resolve the whole
issue, if a tool exists for those who want implicit self. After all,
if -you- have the itch...
Perhaps you could leverage off of EasyExtend?
"EasyExtend (EE) is a preprocessor generator and metaprogramming
framework written in pure Python and integrated with CPython. The main
purpose of EasyExtend is the creation of extension languages i.e.
adding custom syntax and semantics to Python."