Re: class implementation
kolmapäev, 9. oktoober 2013 2:55.28 UTC+3 kirjutas Cameron Simpson:
On 08Oct2013 01:20, wrote:
I cant just subclassing doesent work. It seem the init method of the source
class also calls out another class. And the problem is, i can subclass the
other class to with the required function but the end result is that it
doesent work, since the source class cant accsess the subclass functions.
The source code is pykkar.
https://courses.cs.ut.ee/all/MTAT.03.100/2012_fall/uploads/opik/_downloads/pykkar.py
I want to add it a new ability called left(). I cant manipulate the source
class, cause then my comp will be the only one where the program runs.
class pykkar_l(Pykkar):
def left(self):
self._world.execute(left)
[...]
You normally need to call the superclasses' __init__ method as well.
Example:
def __init__(self):
Pykkar.__init__(self)
... any of your own init stuff ...
Likewise for your world_l class.
BTW, it is conventional to start class names with an upper case letters. Just
style, but it helps other people when reading your code.
Cheers,
--
It looks like you've got Mister Bus Error installed.- tjc
OK so I did a took time of and read the pykkar code through. abd I found that
there is a third class i have to implement.
This Is the pykkar sourcecode
# coding=UTF-8
Intro and usage
===
Pykkar is a virtual robot living in a virtual world. It can step, turn 90
degrees right,
paint floor tiles, take and put down traffic cones and push boxes. It can detect
whether there is a wall or other obstacle ahead or whether it's standing on a
painted
tile. It can be commanded by Python code (either procedural or OOP style)
Pykkar's world can be created by a call to ``create_world`` (when using
procedural style)
or by instantiating class ``World`` (OOP style). Both take single argument,
which is
a string representation of the world. Lines in the string represent the rows in
the world
map. Each character represents one tile. Meaning of characters:
#wall
space plain floor
.painted floor
bbox on plain floor
Bbox on painted floor
^ v pykkar on plain floor without cone
(caret, greater-than, lowercase v, less-than)
N E S W pykkar on painted floor without cone
1 2 3 4 5 6 7 8 9cone stack on plain floor
Csingle cone on painted floor
Sample:
create_world('''
# #
# 3#
''')
this creates a world where 2x2 floor are is padded with walls. Pykkar is in
north-west
corner of the floor, looking east and in south-east corner there is a stack of
3 traffic
cones.
In procedural style, Pykkar can be commanded by calling global functions
defined in this
module (eg. ``step()``, ``right()``, etc). There are also functions for
querying the
world (``is_wall()``, ``is_box()``, etc). New compound commands can be defined
by defining
new functions in client module.
In OOP style, Pykkar is represented by a separate object of class ``Pykkar``.
In the
start of the program, client code is supposed to create new world (eg. ``w =
World(layout)``)
and a Pykkar living in that world (eg ``p = Pykkar(w)``). Commands are given by
calling
the methods of Pykkar object. New commands should be defined by subclassing
``Pykkar``.
Technical stuff
In order to reserve the main thread for executing commands (this way respective
function calls
can be written in client module's toplevel), tkinter window must run in a
different thread.
Unfortunately, tkinter runs reliably only in the main thread of the process.
For this reason the execution is divided into 2 processes: the main process,
which is just a shallow command proxy and the child process, which runs actual
program
logic and presents the world state in a tkinter window.
Main process (ie. user module) normally begins by creating the world (with
either
``create_world(...)`` or ``World(...)``). This spawns a child process which
creates
tkinter window representing the world. Main process then continues by executing
user-provided function/method calls, which amounts to writing respective
command strings
to child process' stdin and reading results back from child process' stdout.
Main player in child process is an object of class ``_WorldProper``. It keeps
the
data structures about world layout, responds to commands that alter the world
state and runs
a tkinter window. It reads periodically next command from stdin, acts upon it
and writes
result (may be None) to stdout.
NB! as stdout from tkinter process is parsed, you can't just print out debug
information
to sys.stdout. Use sys.stderr instead!
Reading from stdin blocks, as usual. This would make window temporariliy
unresponsive
when
Re: class implementation
On 10Oct2013 11:34, markot...@gmail.com markot...@gmail.com wrote: OK so I did a took time of and read the pykkar code through. abd I found that there is a third class i have to implement. This Is the pykkar sourcecode [... lots and lots of docstring and code ...] [... and finally a little more messgae ...] I did not wan to but the source in here because it is just so god damn long. But some of you wanted it, so here it is :D As a matter of readability, if I really need to include a huge body of text I append it below the end of my message, and say something like this (pretending I were writing your message): OK so I did a took time of and read the pykkar code through. abd I found that there is a third class i have to implement. I've appended the relevant pykkar source below this message. So I have come up with this code: [...] That way your message does not get hidden by the (overly long IMO) included material and readers can get on with looking at your stuff, knowing that if necessary they can wade through the other stuff. Cheers, -- Cameron Simpson c...@zip.com.au Any profit should go to Arnie's `get the daemon carved on Mount Rushmore' fund. - Marty Albini, DOD0550, mar...@sdd.hp.com -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
markot...@gmail.com writes: OK so I did a took time of and read the pykkar code through. abd I found that there is a third class i have to implement. [...] So I have come up with this code from pykkar import * create_world( # # # v# # # # # # # ) class world_täiend(World): def left(self): world.excecute(left) class pykkar_täiend(Pykkar): def left(self): self._world.excecute(left) class _WorldProper_täiend(_WorldProper): def _cmd_right(self): Should that not be _cmd_left? headings = (N,E,S,W) cur_tile = self._get_current_tile() cur_heading_index = headings.index(cur_tile.pykkar_heading) new_heading_index = (cur_heading_index - 1) % 4 cur_tile.pykkar_heading = headings[new_heading_index] self._update_pykkar_image(cur_tile) left() When I run my code I get this error. Traceback (most recent call last): File C:\Users\MarkoPC\Desktop\python\pykkar_test.py, line 21, in module class _WorldProper_täiend(_WorldProper): NameError: name '_WorldProper' is not defined from import * doesn't import names that start with underscore (_). So therefore _WorldProper is not defined. from import * is considered bad practice anyway. It is better just to import the things you need. from pykkar import World, Pykkar, _WorldProper I have looked a bit in this pykkar.py and I think it is badly structured for extension. The three classes are too strongly connected and it is difficult to get three subclasses connected in the proper way without duplicating code. But anyway you will have to do that when you create your world. -- Piet van Oostrum p...@vanoostrum.org WWW: http://pietvanoostrum.com/ PGP key: [8DAE142BE17999C4] -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
Piet van Oostrum p...@vanoostrum.org writes: from import * is considered bad practice anyway. It is better just to import the things you need. from pykkar import World, Pykkar, _WorldProper Or, even better, be explicit: import pykkar … foo = pykkar.World() -- \ “Computer perspective on Moore's Law: Human effort becomes | `\ twice as expensive roughly every two years.” —anonymous | _o__) | Ben Finney -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
I cant just subclassing doesent work. It seem the init method of the source class also calls out another class. And the problem is, i can subclass the other class to with the required function but the end result is that it doesent work, since the source class cant accsess the subclass functions. The source code is pykkar. https://courses.cs.ut.ee/all/MTAT.03.100/2012_fall/uploads/opik/_downloads/pykkar.py I want to add it a new ability called left(). I cant manipulate the source class, cause then my comp will be the only one where the program runs. class pykkar_l(Pykkar): def left(self): self._world.execute(left) def _cmd_left(self): headings = (N,E,S,W) cur_tile = self._get_current_tile() cur_heading_index = headings.index(cur_tile.pykkar_heading) new_heading_index = (cur_heading_index - 1) % 4 cur_tile.pykkar_heading = headings[new_heading_index] self._update_pykkar_image(cur_tile) class world_l(World): def left(self): self._world.execute(left) These are my subclasses. For it to work. Class World, must obtain the method from subclass world_l -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On 08/10/2013 09:20, markot...@gmail.com wrote: To whom and to what are you replying? -- Roses are red, Violets are blue, Most poems rhyme, But this one doesn't. Mark Lawrence -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On 8/10/2013 04:20, markot...@gmail.com wrote: I cant just subclassing doesent work. I can't parse that sentence. It seem the init method of the source class also calls out another class. And the problem is, i can subclass the other class to with the required function but the end result is that it doesent work, since the source class cant accsess the subclass functions. What's a source class? If you mean parent class, then say so. Otherwise, if you give it a name, we might be able to follow. But source and other don't narrow the field very much. A parent class can certainly access the child class (subclass) methods (not functions). But only if the instance (self) is an instance of the child class. That's the whole point of subclassing. The source code is pykkar. https://courses.cs.ut.ee/all/MTAT.03.100/2012_fall/uploads/opik/_downloads/pykkar.py I want to add it a new ability called left(). I cant manipulate the source class, cause then my comp will be the only one where the program runs. class pykkar_l(Pykkar): def left(self): self._world.execute(left) def _cmd_left(self): headings = (N,E,S,W) cur_tile = self._get_current_tile() cur_heading_index = headings.index(cur_tile.pykkar_heading) new_heading_index = (cur_heading_index - 1) % 4 cur_tile.pykkar_heading = headings[new_heading_index] self._update_pykkar_image(cur_tile) class world_l(World): def left(self): self._world.execute(left) These are my subclasses. For it to work. Class World, must obtain the method from subclass world_l Then it sounds like you should make sure that the global value world in that module is an instance of your world_l class, rather than an instance or World. And that the proxy is an instance of pykkar_l rather than of Pykkar. import pykkar layout = fdlkjdsljdslfkjsdljfdsf pykkar.world = world_I(layout) ??? = pykkar_l(pykkar.world) You don't show your own top-level code, so I can't integrate it in. By the way, it's conventional to use uppercase for class names, and lowercase for instances of those classes. I'm astounded that your class is using eval and multiprocessing before understanding classes and subclasses. -- DaveA -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
Parent class is at the link. -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On Tue, 08 Oct 2013 15:05:26 +0100, markot...@gmail.com wrote: Parent class is at the link. Please quote some context when you reply. What link? Then again, I'm not about to click on some random link someone posts to a newsgroup. Apart from being one of the classic ways to get a virus onto my computer, it's rather selfish of you. While your newsgroup posting will stay around essentially forever, the link will eventually rot. At some point in the future, no one will be able to follow that link, so no one will be able to learn from what you have done. Please show your working, it makes it so much easier for the rest of us to understand what you meant when you use terms so loosely! -- Rhodri James *-* Wildebeest Herder to the Masses -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On 08Oct2013 01:20, markot...@gmail.com markot...@gmail.com wrote: I cant just subclassing doesent work. It seem the init method of the source class also calls out another class. And the problem is, i can subclass the other class to with the required function but the end result is that it doesent work, since the source class cant accsess the subclass functions. The source code is pykkar. https://courses.cs.ut.ee/all/MTAT.03.100/2012_fall/uploads/opik/_downloads/pykkar.py I want to add it a new ability called left(). I cant manipulate the source class, cause then my comp will be the only one where the program runs. class pykkar_l(Pykkar): def left(self): self._world.execute(left) [...] You normally need to call the superclasses' __init__ method as well. Example: def __init__(self): Pykkar.__init__(self) ... any of your own init stuff ... Likewise for your world_l class. BTW, it is conventional to start class names with an upper case letters. Just style, but it helps other people when reading your code. Cheers, -- Cameron Simpson c...@zip.com.au It looks like you've got Mister Bus Error installed.- tjc -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
There is this class file, it has its functions and variables. Now im greating my program, that uses the funcions from the class. BUt there are some functions missing from the class. So i want to add some extra funtions to the class, whidout altering the original source code, but by extending it in my code. But for that i need to use some variables that exsist in the original class. Is there a way i can acccsess them? -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On 10/6/2013 9:15 AM, markot...@gmail.com wrote: There is this class file, it has its functions and variables. Now im greating my program, that uses the funcions from the class. BUt there are some functions missing from the class. So i want to add some extra funtions to the class, whidout altering the original source code, but by extending it in my code. But for that i need to use some variables that exsist in the original class. Is there a way i can acccsess them? I though you already got an answer: subclass the class. -- Terry Jan Reedy -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On Sun, 06 Oct 2013 06:15:51 -0700, markotaht wrote: There is this class file, it has its functions and variables. What's a class file? Do you mean a file containing only a single class? Now im greating my program, that uses the funcions from the class. They are called methods. BUt there are some functions missing from the class. So i want to add some extra funtions to the class, whidout altering the original source code, but by extending it in my code. But for that i need to use some variables that exsist in the original class. Is there a way i can acccsess them? When you say variables, we prefer to say attributes. A string variable is a variable that holds a string. An int variable is a variable that holds an int. A list variable is a variable that holds a list. A float variable is a variable that holds a float. So... ...a class variable is a variable that holds a class, and an instance variable is a variable that holds an instance. When extending classes, you access attributes exactly the same way you would access them if you were writing the class in the first place. class Test(object): def __init__(self, arg): self.arg = arg # Store the arg as an instance attribute. def method(self): print(arg is, self.arg) class NewTest(Test): # subclass to add new methods def add_one(self): return self.arg+1 For experts only: sometimes you need to extend the class itself. You can do that by adding methods to the class: def minus_one(self): return self.arg-1 NewTest.minus_one = minus_one -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On Tuesday, October 1, 2013 3:34:08 AM UTC+8, Dave Angel wrote: On 30/9/2013 08:41, markot...@gmail.com wrote: under variables, i mean, the int's and lists and strings and floats that the parent class uses. IF in parent class there is variable called location, then can i use the same variable in my sub class. Python doesn't actually have variables, but the things it documents as variables are local names within a method. Those are not visible outside of the method, regardless of whether you're in a class or a subclass. But perhaps you mean attributes. There are both class attributes and instance attributes, and the behavior is quite different. Roughly speaking a class attribute occurs only once per class, and all code can read its value with either Class.my_attrib or instance.my_attrib. It can be written with Class.my_attrib. On the other hand, instance attributes are usable by instance.my_attrib, regardless of whether the instance is a base class An instance is an object of some class that could have its own attributes i.e. instance priviate properties during the run time. or a child class. Each instance of the class gets a separate copy of such an attribute. They are normally defined in the __init__() method. If you don't happen to know the difference between a class an an instance of that class, then all the above will look like gibberish, and you need to do some studying first. -- DaveA -- https://mail.python.org/mailman/listinfo/python-list
class implementation
Is there a way to give a class extra functions whidout editing the .py file where the class is located? -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
markot...@gmail.com wrote: Is there a way to give a class extra functions whidout editing the .py file where the class is located? A clean way is subclassing: import vehicles class FlyingCar(vehicles.Car): def lift_off(self): pass flying_car = FlyingCar() flying_car.lift_off() -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
esmaspäev, 30. september 2013 11:43.19 UTC+3 kirjutas mark...@gmail.com: Is there a way to give a class extra functions whidout editing the .py file where the class is located? But does it have all the variables that the main class have? -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
markot...@gmail.com wrote: esmaspäev, 30. september 2013 11:43.19 UTC+3 kirjutas mark...@gmail.com: Is there a way to give a class extra functions whidout editing the .py file where the class is located? But does it have all the variables that the main class have? Yes. You can invoke all methods of Car on a FlyingCar instance. If you don't define an __init__() method in FlyingCar the initializer of the parent class will be invoked which typically sets a few attributes (I think this is what you mean by variables; if not: please clarify). So just try it out. If you don't get your code to work you can post it here and ask for help on an actual piece of Python. -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
under variables, i mean, the int's and lists and strings and floats that the parent class uses. IF in parent class there is variable called location, then can i use the same variable in my sub class. -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
markot...@gmail.com wrote: under variables, i mean, the int's and lists and strings and floats that the parent class uses. IF in parent class there is variable called location, then can i use the same variable in my sub class. Please show us some code. Thankyou. -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On Mon, Sep 30, 2013 at 9:02 AM, Peter Otten __pete...@web.de wrote: markot...@gmail.com wrote: under variables, i mean, the int's and lists and strings and floats that the parent class uses. IF in parent class there is variable called location, then can i use the same variable in my sub class. Please show us some code. Thankyou. -- https://mail.python.org/mailman/listinfo/python-list You should start by learning about classes -- perhaps here: http://docs.python.org/2/tutorial/classes.html#classes Then, try writing some code using classes or extending a class. Then come back when something doesn't work as expected -- Joel Goldstick http://joelgoldstick.com -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
markot...@gmail.com writes: under variables, i mean, the int's and lists and strings and floats that the parent class uses. IF in parent class there is variable called location, then can i use the same variable in my sub class. Do you mean class variables or instance variables? -- Piet van Oostrum p...@vanoostrum.org WWW: http://pietvanoostrum.com/ PGP key: [8DAE142BE17999C4] -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On 30/9/2013 08:41, markot...@gmail.com wrote: under variables, i mean, the int's and lists and strings and floats that the parent class uses. IF in parent class there is variable called location, then can i use the same variable in my sub class. Python doesn't actually have variables, but the things it documents as variables are local names within a method. Those are not visible outside of the method, regardless of whether you're in a class or a subclass. But perhaps you mean attributes. There are both class attributes and instance attributes, and the behavior is quite different. Roughly speaking a class attribute occurs only once per class, and all code can read its value with either Class.my_attrib or instance.my_attrib. It can be written with Class.my_attrib. On the other hand, instance attributes are usable by instance.my_attrib, regardless of whether the instance is a base class or a child class. Each instance of the class gets a separate copy of such an attribute. They are normally defined in the __init__() method. If you don't happen to know the difference between a class an an instance of that class, then all the above will look like gibberish, and you need to do some studying first. -- DaveA -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On 9/30/13 3:34 PM, Dave Angel wrote: Python doesn't actually have variables, but the things it documents as variables are local names within a method. Those are not visible outside of the method, regardless of whether you're in a class or a subclass. Why does this meme persist!? Of course Python has variables, they just don't work like C variables do. If you'd like to know the details: http://nedbatchelder.com/text/names.html --Ned. -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On Mon, Sep 30, 2013, at 17:28, Ned Batchelder wrote: On 9/30/13 3:34 PM, Dave Angel wrote: Python doesn't actually have variables, but the things it documents as variables are local names within a method. Those are not visible outside of the method, regardless of whether you're in a class or a subclass. Why does this meme persist!? Of course Python has variables, they just don't work like C variables do. If you'd like to know the details: http://nedbatchelder.com/text/names.html Wait a minute, how exactly are C variables supposed to be different from this? -- https://mail.python.org/mailman/listinfo/python-list
Python variables? [was Re: class implementation]
On 09/30/2013 02:28 PM, Ned Batchelder wrote: On 9/30/13 3:34 PM, Dave Angel wrote: Python doesn't actually have variables, but the things it documents as variables are local names within a method. Those are not visible outside of the method, regardless of whether you're in a class or a subclass. Why does this meme persist!? Of course Python has variables, they just don't work like C variables do. If you'd like to know the details: http://nedbatchelder.com/text/names.html Because Python's model is different enough that it usually makes thinking about it simpler to stay away from the word 'variable'; in every other language I have used a variable is a box, but in Python it's a label for a box. From your blog: Names are Python's variables: they refer to values, and those values can change (vary) over the course of your program. This is partially incorrect. If the value referred to by the name is immutable, then it cannot change; perhaps you meant to say that which object the name points to can vary over time? -- ~Ethan~ -- https://mail.python.org/mailman/listinfo/python-list
Re: Python variables? [was Re: class implementation]
On 9/30/13 6:02 PM, Ethan Furman wrote: On 09/30/2013 02:28 PM, Ned Batchelder wrote: On 9/30/13 3:34 PM, Dave Angel wrote: Python doesn't actually have variables, but the things it documents as variables are local names within a method. Those are not visible outside of the method, regardless of whether you're in a class or a subclass. Why does this meme persist!? Of course Python has variables, they just don't work like C variables do. If you'd like to know the details: http://nedbatchelder.com/text/names.html Because Python's model is different enough that it usually makes thinking about it simpler to stay away from the word 'variable'; in every other language I have used a variable is a box, but in Python it's a label for a box. It might help C programmers to stay away from variable, but some people claim we should avoid the word so as not to confuse beginners. That's just silly. Beginners have no holdover concepts from C. Lots of languages use the same names and values model that Python does: Javascript, Java, Ruby, Lisp, etc. From your blog: Names are Python's variables: they refer to values, and those values can change (vary) over the course of your program. This is partially incorrect. If the value referred to by the name is immutable, then it cannot change; perhaps you meant to say that which object the name points to can vary over time? Yes, I meant that 1) names refer to values, and 2) a name can refer to different values over the course of a program. Hence, the value varies, hence, a variable. In fact, it's more accurate to say that Python has no constants! :) --Ned. -- ~Ethan~ -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On Mon, 30 Sep 2013 17:28:30 -0400, Ned Batchelder wrote: On 9/30/13 3:34 PM, Dave Angel wrote: Python doesn't actually have variables, but the things it documents as variables are local names within a method. Those are not visible outside of the method, regardless of whether you're in a class or a subclass. Why does this meme persist!? Of course Python has variables, they just don't work like C variables do. If you'd like to know the details: http://nedbatchelder.com/text/names.html I'm not convinced that Python variables are different from C variables is a better way to get through to people than Python doesn't have variables, it has name bindings. Of course, *technically* the first statement is accurate, and the second relies on a definition of variable that is not universal. The question is which is more effective at getting the differences between the two programming models through to the reader. I can't speak for others, but in my own experience, I never *quite* understood the semantic differences between Python name bindings and Pascal variables until I came across the meme Python has no variables. -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On Mon, 30 Sep 2013 05:41:16 -0700, markotaht wrote: under variables, i mean, the int's and lists and strings and floats that the parent class uses. IF in parent class there is variable called location, then can i use the same variable in my sub class. Firstly, in Python circles we prefer to call them attributes rather than variables. Since this is Python, it is trivially easy to test this for yourself. Start an interactive Python interpreter, and then in under a dozen lines you can test it: py class Test: ... attr = Hello World! # Shared class attribute. ... py class MyTest(Test): ... pass ... py x = MyTest() py x.attr 'Hello World!' Works perfectly! (It would be a funny programming language where it didn't, since this is one of the most fundamental parts of inheritance. A language that didn't do something equivalent to this couldn't really claim to be object-oriented.) -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: Python variables? [was Re: class implementation]
On Tue, 01 Oct 2013 00:45:06 +0100, Ned Batchelder n...@nedbatchelder.com wrote: On 9/30/13 6:02 PM, Ethan Furman wrote: From your blog: Names are Python's variables: they refer to values, and those values can change (vary) over the course of your program. This is partially incorrect. If the value referred to by the name is immutable, then it cannot change; perhaps you meant to say that which object the name points to can vary over time? Yes, I meant that 1) names refer to values, and 2) a name can refer to different values over the course of a program. Hence, the value varies, hence, a variable. Yes, except no. The problem is that word value, which I can practically see morphing its meaning through that paragraph. Names refer to objects, which have values or interpretations or however you choose to say it. Some (mutable) objects can change their value, some (immutable) can't. Independently, names can refer to different objects, which may or may not have different values (or indeed concepts of value). When you say The value varies, it begs the question Which 'the value'? In fact, it's more accurate to say that Python has no constants! :) Or, alternatively, that Python has many constants, such as all those immutable integers cached around the place :-) What it doesn't have is fixed bindings. -- Rhodri James *-* Wildebeest Herder to the Masses -- https://mail.python.org/mailman/listinfo/python-list
Re: class implementation
On 09/30/2013 04:45 PM, Steven D'Aprano wrote: I can't speak for others, but in my own experience, I never *quite* understood the semantic differences between Python name bindings and Pascal variables until I came across the meme Python has no variables. +1 -- https://mail.python.org/mailman/listinfo/python-list
Basic class implementation question
I can't get call a class for some reason. This must be one of those newbie questions I hear so much about: class wontwork: def really(): print Hello World wontwork.really() This returns (as an error): Traceback (most recent call last): File pyshell#4, line 1, in module wontwork.really() TypeError: unbound method really() must be called with wontwork instance as first argument (got nothing instead) Any ideas? -- http://mail.python.org/mailman/listinfo/python-list
Re: Basic class implementation question
Try this. class wontwork: def really(self): print Hello World wontwork().really() On Tue, Apr 1, 2008 at 9:43 PM, [EMAIL PROTECTED] wrote: I can't get call a class for some reason. This must be one of those newbie questions I hear so much about: class wontwork: def really(): print Hello World wontwork.really() This returns (as an error): Traceback (most recent call last): File pyshell#4, line 1, in module wontwork.really() TypeError: unbound method really() must be called with wontwork instance as first argument (got nothing instead) Any ideas? -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Basic class implementation question
You might want to consult this. http://www.ibiblio.org/g2swap/byteofpython/read/object-methods.html On Tue, Apr 1, 2008 at 9:43 PM, [EMAIL PROTECTED] wrote: I can't get call a class for some reason. This must be one of those newbie questions I hear so much about: class wontwork: def really(): print Hello World wontwork.really() This returns (as an error): Traceback (most recent call last): File pyshell#4, line 1, in module wontwork.really() TypeError: unbound method really() must be called with wontwork instance as first argument (got nothing instead) Any ideas? -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Reuse base-class implementation of classmethod?
David Wahler wrote: what's the magic needed to reuse the base-class implementation of a classmethod? class A(object): @classmethod def foo(cls, a,b): # do something pass class B(A): @classmethod def foo(cls, a, b): A.foo(cls, a, b) # WRONG! I need to call the base-class classmethod to reuse its implementation, but I'd like to pass the derived class as first argument. -- Giovanni Bajo See the super object. In your case, it can be used like this: class B(A): @classmethod def foo(cls, a, b): super(B, cls).foo(a, b) Ah thanks, I did not realize that super() was the only way of doing the right thing here! -- Giovanni Bajo -- http://mail.python.org/mailman/listinfo/python-list
Reuse base-class implementation of classmethod?
Hello, what's the magic needed to reuse the base-class implementation of a classmethod? class A(object): @classmethod def foo(cls, a,b): # do something pass class B(A): @classmethod def foo(cls, a, b): A.foo(cls, a, b) # WRONG! I need to call the base-class classmethod to reuse its implementation, but I'd like to pass the derived class as first argument. -- Giovanni Bajo -- http://mail.python.org/mailman/listinfo/python-list
Re: Reuse base-class implementation of classmethod?
Giovanni Bajo wrote: Hello, what's the magic needed to reuse the base-class implementation of a classmethod? class A(object): @classmethod def foo(cls, a,b): # do something pass class B(A): @classmethod def foo(cls, a, b): A.foo(cls, a, b) # WRONG! I need to call the base-class classmethod to reuse its implementation, but I'd like to pass the derived class as first argument. -- Giovanni Bajo See the super object. In your case, it can be used like this: class B(A): @classmethod def foo(cls, a, b): super(B, cls).foo(a, b) This all assumes you want to modify the behavior of foo in a subclass. If not, of course, you don't need to override it at all. -- David -- http://mail.python.org/mailman/listinfo/python-list
Re: Reuse base-class implementation of classmethod?
On Tue, 01 Nov 2005 00:24:37 GMT, Giovanni Bajo [EMAIL PROTECTED] wrote:
Hello,
what's the magic needed to reuse the base-class implementation of a
classmethod?
class A(object):
@classmethod
def foo(cls, a,b):
# do something
pass
class B(A):
@classmethod
def foo(cls, a, b):
A.foo(cls, a, b) # WRONG!
I need to call the base-class classmethod to reuse its implementation, but I'd
like to pass the derived class as first argument.
--
Giovanni Bajo
Maybe define a funny-class-method decorator?
(nothing below tested beyond what you see ;-)
def funnycm(m):
... return property(lambda cls: m.__get__(type(cls), type(type(cls
...
class A(object):
... @funnycm
... def foo(cls, a, b):
... print cls, a, b # do something
...
class B(A):
... pass # just inherit
...
a=A()
a.foo(1,2)
class '__main__.A' 1 2
b=B()
b.foo(1,2)
class '__main__.B' 1 2
Or more directly, a custom descriptor (with dynamic method replacement for good
measure ;-)
class funnycm(object):
... def __init__(self, f): self._f = f
... def __get__(self, inst, cls=None):
... return self._f.__get__(inst is None and cls or type(inst))
... def __set__(self, inst, m): self._f = m # replace method
...
class A(object):
... @funnycm
... def foo(cls, a, b):
... print cls, a, b # do something
...
class B(A):
... pass # just inherit
...
a=A()
a.foo(1,2)
class '__main__.A' 1 2
b=B()
b.foo(1,2)
class '__main__.B' 1 2
A.foo(3,4)
class '__main__.A' 3 4
B.foo(3,4)
class '__main__.B' 3 4
a.foo = lambda cls, *args: repr(args)
a.foo('what','now','then?')
('what', 'now', 'then?')
b.foo('eh?')
('eh?',)
B.foo()
'()'
Vary to taste ;-)
Regards,
Bengt Richter
--
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