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I have no class

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  I have no class Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-11-22 21:47 -0500
    Re: I have no class random832@fastmail.us - 2014-11-22 22:08 -0500
      Re: I have no class Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-11-22 22:16 -0500
    Re: I have no class Rustom Mody <rustompmody@gmail.com> - 2014-11-22 19:09 -0800
      Re: I have no class Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-11-22 22:18 -0500
    Re: I have no class Ned Batchelder <ned@nedbatchelder.com> - 2014-11-22 22:14 -0500
      Re: I have no class Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-11-22 22:35 -0500
        Re: I have no class Joel Goldstick <joel.goldstick@gmail.com> - 2014-11-22 22:52 -0500
          Re: I have no class Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-11-22 23:15 -0500
            Re: I have no class Chris Angelico <rosuav@gmail.com> - 2014-11-23 17:00 +1100
              Re: I have no class Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-11-23 05:52 -0500
                Re: I have no class Dave Angel <davea@davea.name> - 2014-11-23 10:16 -0500
                  Re: I have no class Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-11-23 10:54 -0500
                    Re: I have no class Dave Angel <davea@davea.name> - 2014-11-23 11:14 -0500
                      Re: I have no class Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-11-23 11:49 -0500
                        Re: I have no class Chris Angelico <rosuav@gmail.com> - 2014-11-24 03:59 +1100
                        Re: I have no class Rustom Mody <rustompmody@gmail.com> - 2014-11-23 09:02 -0800
                          Re: I have no class Steven D'Aprano <steve@pearwood.info> - 2014-11-24 04:21 +0000
                            Re: I have no class Dave Angel <davea@davea.name> - 2014-11-24 00:11 -0500
                            Re: I have no class Chris Angelico <rosuav@gmail.com> - 2014-11-24 16:11 +1100
                              Re: I have no class Dan Sommers <dan@tombstonezero.net> - 2014-11-24 13:44 +0000
                                Re: I have no class Chris Angelico <rosuav@gmail.com> - 2014-11-25 00:48 +1100
                            Re: I have no class Dave Angel <davea@davea.name> - 2014-11-24 00:20 -0500
                            Re: I have no class Chris Angelico <rosuav@gmail.com> - 2014-11-24 16:21 +1100
                            Re: I have no class Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-11-24 13:47 -0500
        Re: I have no class Rustom Mody <rustompmody@gmail.com> - 2014-11-22 19:55 -0800
          Re: I have no class Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-11-22 23:19 -0500
          Re: I have no class Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-11-23 15:35 +0000

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#81315 — I have no class

What do I need to do to make a and b have different values?
import random
class RPS:
    throw=random.randrange(3)
a=RPS
b=RPS

print ("a ",a.throw)
print ("b ",b.throw)
if a.throw == b.throw:
    print("Tie")
elif (a.throw - b.throw)%3==1:    
    print("a Wins")
else:    
    print("b Wins")  

---------
I tried:  

class RPS:
    def __init__(self):
        self.throw=random.randrange(3)

AttributeError: type object 'RPS' has no attribute 'throw'
    

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#81316

On Sat, Nov 22, 2014, at 21:47, Seymore4Head wrote:
> What do I need to do to make a and b have different values?
> import random
> class RPS:
>     throw=random.randrange(3)
> a=RPS
> b=RPS
> 
> print ("a ",a.throw)
> print ("b ",b.throw)
> if a.throw == b.throw:
>     print("Tie")
> elif (a.throw - b.throw)%3==1:    
>     print("a Wins")
> else:    
>     print("b Wins")  
> 
> ---------
> I tried:  
> 
> class RPS:
>     def __init__(self):
>         self.throw=random.randrange(3)
> 
> AttributeError: type object 'RPS' has no attribute 'throw'

You need that class, and also a=RPS(); b=RPS().

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#81320

On Sat, 22 Nov 2014 22:08:31 -0500, random832@fastmail.us wrote:

>
>
>On Sat, Nov 22, 2014, at 21:47, Seymore4Head wrote:
>> What do I need to do to make a and b have different values?
>> import random
>> class RPS:
>>     throw=random.randrange(3)
>> a=RPS
>> b=RPS
>> 
>> print ("a ",a.throw)
>> print ("b ",b.throw)
>> if a.throw == b.throw:
>>     print("Tie")
>> elif (a.throw - b.throw)%3==1:    
>>     print("a Wins")
>> else:    
>>     print("b Wins")  
>> 
>> ---------
>> I tried:  
>> 
>> class RPS:
>>     def __init__(self):
>>         self.throw=random.randrange(3)
>> 
>> AttributeError: type object 'RPS' has no attribute 'throw'
>
>You need that class, and also a=RPS(); b=RPS().

That works.
Thanks

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#81317

On Sunday, November 23, 2014 8:17:24 AM UTC+5:30, Seymore4Head wrote:
> What do I need to do to make a and b have different values?
> import random
> class RPS:
>     throw=random.randrange(3)
> a=RPS
> b=RPS
> 
> print ("a ",a.throw)
> print ("b ",b.throw)
> if a.throw == b.throw:
>     print("Tie")
> elif (a.throw - b.throw)%3==1:    
>     print("a Wins")
> else:    
>     print("b Wins")  
> 
> ---------
> I tried:  
> 
> class RPS:
>     def __init__(self):
>         self.throw=random.randrange(3)
> 
> AttributeError: type object 'RPS' has no attribute 'throw'

Works as far as I can see:

import random
class RPS:
    def __init__(self):
        self.throw=random.randrange(3)
-----------------
>>> a = RPS()
>>> a.throw
0
>>> a = RPS()
>>> a.throw
2
>>> a = RPS()
>>> a.throw
2

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#81321

On Sat, 22 Nov 2014 19:09:27 -0800 (PST), Rustom Mody
<rustompmody@gmail.com> wrote:

>On Sunday, November 23, 2014 8:17:24 AM UTC+5:30, Seymore4Head wrote:
>> What do I need to do to make a and b have different values?
>> import random
>> class RPS:
>>     throw=random.randrange(3)
>> a=RPS
>> b=RPS
>> 
>> print ("a ",a.throw)
>> print ("b ",b.throw)
>> if a.throw == b.throw:
>>     print("Tie")
>> elif (a.throw - b.throw)%3==1:    
>>     print("a Wins")
>> else:    
>>     print("b Wins")  
>> 
>> ---------
>> I tried:  
>> 
>> class RPS:
>>     def __init__(self):
>>         self.throw=random.randrange(3)
>> 
>> AttributeError: type object 'RPS' has no attribute 'throw'
>
>Works as far as I can see:
>
>import random
>class RPS:
>    def __init__(self):
>        self.throw=random.randrange(3)
>-----------------
>>>> a = RPS()
>>>> a.throw
>0
>>>> a = RPS()
>>>> a.throw
>2
>>>> a = RPS()
>>>> a.throw
>2
It works when you remember to include the ()
I am still making rookie mistakes.
Thanks

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#81319

On 11/22/14 9:47 PM, Seymore4Head wrote:
> What do I need to do to make a and b have different values?
> import random
> class RPS:
>      throw=random.randrange(3)
> a=RPS
> b=RPS

This simply makes a and b into other names for the class RPS. To 
instantiate a class to make an object, you have to call it:

     a = RPS()
     b = RPS()

> ---------
> I tried:
>
> class RPS:
>      def __init__(self):
>          self.throw=random.randrange(3)
>
> AttributeError: type object 'RPS' has no attribute 'throw'

This is the right way to define the class (almost: in Py 2, you should 
derive from object). Once you make an object from it, you will have what 
you want:

     class RPS(object):
         def __init__(self):
             self.throw = random.randrange(3)

     a = RPS()
     b = RPS()
     print a.throw
     print b.throw


-- 
Ned Batchelder, http://nedbatchelder.com

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#81322

On Sat, 22 Nov 2014 22:14:21 -0500, Ned Batchelder
<ned@nedbatchelder.com> wrote:

>On 11/22/14 9:47 PM, Seymore4Head wrote:
>> What do I need to do to make a and b have different values?
>> import random
>> class RPS:
>>      throw=random.randrange(3)
>> a=RPS
>> b=RPS
>
>This simply makes a and b into other names for the class RPS. To 
>instantiate a class to make an object, you have to call it:
>
>     a = RPS()
>     b = RPS()
>
>> ---------
>> I tried:
>>
>> class RPS:
>>      def __init__(self):
>>          self.throw=random.randrange(3)
>>
>> AttributeError: type object 'RPS' has no attribute 'throw'
>
>This is the right way to define the class (almost: in Py 2, you should 
>derive from object). Once you make an object from it, you will have what 
>you want:
>
>     class RPS(object):
>         def __init__(self):
>             self.throw = random.randrange(3)
>
>     a = RPS()
>     b = RPS()
>     print a.throw
>     print b.throw

Now I am trying to add a dictionary, but it is broke too.

How do I fix:
class RPS:
    key={0:"rock", 1:"paper",2:"scissors"};
    def __init__(self):
        self.throw=random.randrange(3)
        self.key=key[self.throw]

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#81323

On Sat, Nov 22, 2014 at 10:35 PM, Seymore4Head
<Seymore4Head@hotmail.invalid> wrote:
> On Sat, 22 Nov 2014 22:14:21 -0500, Ned Batchelder
> <ned@nedbatchelder.com> wrote:
>
>>On 11/22/14 9:47 PM, Seymore4Head wrote:
>>> What do I need to do to make a and b have different values?
>>> import random
>>> class RPS:
>>>      throw=random.randrange(3)
>>> a=RPS
>>> b=RPS
>>
>>This simply makes a and b into other names for the class RPS. To
>>instantiate a class to make an object, you have to call it:
>>
>>     a = RPS()
>>     b = RPS()
>>
>>> ---------
>>> I tried:
>>>
>>> class RPS:
>>>      def __init__(self):
>>>          self.throw=random.randrange(3)
>>>
>>> AttributeError: type object 'RPS' has no attribute 'throw'
>>
>>This is the right way to define the class (almost: in Py 2, you should
>>derive from object). Once you make an object from it, you will have what
>>you want:
>>
>>     class RPS(object):
>>         def __init__(self):
>>             self.throw = random.randrange(3)
>>
>>     a = RPS()
>>     b = RPS()
>>     print a.throw
>>     print b.throw
>
> Now I am trying to add a dictionary, but it is broke too.
>
> How do I fix:
> class RPS:
>     key={0:"rock", 1:"paper",2:"scissors"};
>     def __init__(self):
>         self.throw=random.randrange(3)
>         self.key=key[self.throw]
> --
> https://mail.python.org/mailman/listinfo/python-list

can you please show traceback and output?

-- 
Joel Goldstick
http://joelgoldstick.com

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#81326

On Sat, 22 Nov 2014 22:52:33 -0500, Joel Goldstick
<joel.goldstick@gmail.com> wrote:

>On Sat, Nov 22, 2014 at 10:35 PM, Seymore4Head
><Seymore4Head@hotmail.invalid> wrote:
>> On Sat, 22 Nov 2014 22:14:21 -0500, Ned Batchelder
>> <ned@nedbatchelder.com> wrote:
>>
>>>On 11/22/14 9:47 PM, Seymore4Head wrote:
>>>> What do I need to do to make a and b have different values?
>>>> import random
>>>> class RPS:
>>>>      throw=random.randrange(3)
>>>> a=RPS
>>>> b=RPS
>>>
>>>This simply makes a and b into other names for the class RPS. To
>>>instantiate a class to make an object, you have to call it:
>>>
>>>     a = RPS()
>>>     b = RPS()
>>>
>>>> ---------
>>>> I tried:
>>>>
>>>> class RPS:
>>>>      def __init__(self):
>>>>          self.throw=random.randrange(3)
>>>>
>>>> AttributeError: type object 'RPS' has no attribute 'throw'
>>>
>>>This is the right way to define the class (almost: in Py 2, you should
>>>derive from object). Once you make an object from it, you will have what
>>>you want:
>>>
>>>     class RPS(object):
>>>         def __init__(self):
>>>             self.throw = random.randrange(3)
>>>
>>>     a = RPS()
>>>     b = RPS()
>>>     print a.throw
>>>     print b.throw
>>
>> Now I am trying to add a dictionary, but it is broke too.
>>
>> How do I fix:
>> class RPS:
>>     key={0:"rock", 1:"paper",2:"scissors"};
>>     def __init__(self):
>>         self.throw=random.randrange(3)
>>         self.key=key[self.throw]
>> --
>> https://mail.python.org/mailman/listinfo/python-list
>
>can you please show traceback and output?
Traceback (most recent call last):
  File "C:\Documents and Settings\Administrator\Desktop\rps.py", line
7, in <module>
    a=RPS()
  File "C:\Documents and Settings\Administrator\Desktop\rps.py", line
6, in __init__
    self.key=key[self.throw]
NameError: name 'key' is not defined

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#81331

On Sun, Nov 23, 2014 at 3:15 PM, Seymore4Head
<Seymore4Head@hotmail.invalid> wrote:
> Traceback (most recent call last):
>   File "C:\Documents and Settings\Administrator\Desktop\rps.py", line
> 7, in <module>
>     a=RPS()
>   File "C:\Documents and Settings\Administrator\Desktop\rps.py", line
> 6, in __init__
>     self.key=key[self.throw]
> NameError: name 'key' is not defined

This information is far more helpful than "it is broke". Note how it
says that the name 'key' is not defined? You're expecting that it
would be defined, because you defined it a few lines earlier. So
here's a more useful way to ask the question:

-- cut --
I'm trying to use a dictionary to translate throw numbers into
descriptions, but even though the dictionary has been defined, Python
is telling me it hasn't.

import random
class RPS:
    key={0:"rock", 1:"paper",2:"scissors"};
    def __init__(self):
        self.throw=random.randrange(3)
        self.key=key[self.throw]
a=RPS()

Traceback (most recent call last):
  File "C:\Documents and Settings\Administrator\Desktop\rps.py", line
7, in <module>
    a=RPS()
  File "C:\Documents and Settings\Administrator\Desktop\rps.py", line
6, in __init__
    self.key=key[self.throw]
NameError: name 'key' is not defined

It seems to me that 'key' is defined on line 3. Can anyone explain
what's happening here? Thanks!
-- cut --

Note that I've posted the *entire* code of your script (it's a
reconstruction, but I suspect it's fairly close; there might be more
code after that, but it's not affecting anything), and included the
traceback in the first message, rather than waiting for someone to ask
for it.

Armed with this information, someone can tell you:

1) Python's namespacing rules mean that 'key' is a part of the RPS
class, and can be referred to as 'self.key' or as 'RPS.key'
2) Use of 'self.key' for the textual form of the throw is shadowing
the first of those reference names (but it's a poor name anyway)
3) A list would work just as well as a dictionary here, since your
indices are sequential and start from zero
4) There's another function in the random module which can do both of
your steps at once.

Thank you for helping us help you help us all!

ChrisA

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#81359

On Sun, 23 Nov 2014 17:00:08 +1100, Chris Angelico <rosuav@gmail.com>
wrote:

>On Sun, Nov 23, 2014 at 3:15 PM, Seymore4Head
><Seymore4Head@hotmail.invalid> wrote:
>> Traceback (most recent call last):
>>   File "C:\Documents and Settings\Administrator\Desktop\rps.py", line
>> 7, in <module>
>>     a=RPS()
>>   File "C:\Documents and Settings\Administrator\Desktop\rps.py", line
>> 6, in __init__
>>     self.key=key[self.throw]
>> NameError: name 'key' is not defined
>
>This information is far more helpful than "it is broke". Note how it
>says that the name 'key' is not defined? You're expecting that it
>would be defined, because you defined it a few lines earlier. So
>here's a more useful way to ask the question:
>
>-- cut --
>I'm trying to use a dictionary to translate throw numbers into
>descriptions, but even though the dictionary has been defined, Python
>is telling me it hasn't.
>
>import random
>class RPS:
>    key={0:"rock", 1:"paper",2:"scissors"};
>    def __init__(self):
>        self.throw=random.randrange(3)
>        self.key=key[self.throw]
>a=RPS()
>
>Traceback (most recent call last):
>  File "C:\Documents and Settings\Administrator\Desktop\rps.py", line
>7, in <module>
>    a=RPS()
>  File "C:\Documents and Settings\Administrator\Desktop\rps.py", line
>6, in __init__
>    self.key=key[self.throw]
>NameError: name 'key' is not defined
>
>It seems to me that 'key' is defined on line 3. Can anyone explain
>what's happening here? Thanks!
>-- cut --
>
>Note that I've posted the *entire* code of your script (it's a
>reconstruction, but I suspect it's fairly close; there might be more
>code after that, but it's not affecting anything), and included the
>traceback in the first message, rather than waiting for someone to ask
>for it.
>
>Armed with this information, someone can tell you:
>
>1) Python's namespacing rules mean that 'key' is a part of the RPS
>class, and can be referred to as 'self.key' or as 'RPS.key'
>2) Use of 'self.key' for the textual form of the throw is shadowing
>the first of those reference names (but it's a poor name anyway)
>3) A list would work just as well as a dictionary here, since your
>indices are sequential and start from zero
>4) There's another function in the random module which can do both of
>your steps at once.
>
>Thank you for helping us help you help us all!
>
>ChrisA

I wish I could explain my problems so precisely.  I will try to do
better in the future.
Thanks

I will also try this using a list instead of a dictionary.

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#81369

On 11/23/2014 05:52 AM, Seymore4Head wrote:
> On Sun, 23 Nov 2014 17:00:08 +1100, Chris Angelico <rosuav@gmail.com>
> wrote:
>
>>
>> 1) Python's namespacing rules mean that 'key' is a part of the RPS
>> class, and can be referred to as 'self.key' or as 'RPS.key'
>> 2) Use of 'self.key' for the textual form of the throw is shadowing
>> the first of those reference names (but it's a poor name anyway)
>> 3) A list would work just as well as a dictionary here, since your
>> indices are sequential and start from zero
>> 4) There's another function in the random module which can do both of
>> your steps at once.
>>
>> Thank you for helping us help you help us all!
>>
>> ChrisA
>
> I wish I could explain my problems so precisely.  I will try to do
> better in the future.
> Thanks
>
> I will also try this using a list instead of a dictionary.
>

And please avoid the shadowing.  It's confusing whenever the same name 
is used for a class attribute and an instance attribute of the same 
class.  it can be useful for defaults and such, but not here.

  class RPS:
      KEY_TABLE={0:"rock", 1:"paper",2:"scissors"};
   or
      KEY_TABLE= ("rock", "paper", "scissors")
      def __init__(self):
          self.throw=random.randrange(3)
          self.key=RPS.KEY_TABLE[self.throw]

Note I also capitalized the tuple name, which is a convention saying we 
don't intend to modify it.

-- 
DaveA

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#81379

On Sun, 23 Nov 2014 10:16:28 -0500, Dave Angel <davea@davea.name>
wrote:

>On 11/23/2014 05:52 AM, Seymore4Head wrote:
>> On Sun, 23 Nov 2014 17:00:08 +1100, Chris Angelico <rosuav@gmail.com>
>> wrote:
>>
>>>
>>> 1) Python's namespacing rules mean that 'key' is a part of the RPS
>>> class, and can be referred to as 'self.key' or as 'RPS.key'
>>> 2) Use of 'self.key' for the textual form of the throw is shadowing
>>> the first of those reference names (but it's a poor name anyway)
>>> 3) A list would work just as well as a dictionary here, since your
>>> indices are sequential and start from zero
>>> 4) There's another function in the random module which can do both of
>>> your steps at once.
>>>
>>> Thank you for helping us help you help us all!
>>>
>>> ChrisA
>>
>> I wish I could explain my problems so precisely.  I will try to do
>> better in the future.
>> Thanks
>>
>> I will also try this using a list instead of a dictionary.
>>
>
>And please avoid the shadowing.  It's confusing whenever the same name 
>is used for a class attribute and an instance attribute of the same 
>class.  it can be useful for defaults and such, but not here.
>
>  class RPS:
>      KEY_TABLE={0:"rock", 1:"paper",2:"scissors"};
>   or
>      KEY_TABLE= ("rock", "paper", "scissors")
>      def __init__(self):
>          self.throw=random.randrange(3)
>          self.key=RPS.KEY_TABLE[self.throw]
>
>Note I also capitalized the tuple name, which is a convention saying we 
>don't intend to modify it.

I just learned by trial and error if I moved "key" out of the class, I
could still use it in the class without having to give it a RPS
extension.

I also changed it to a list and it works fine.

Thanks

key =["rock", "paper", "scissors"]
class RPS:
    def __init__(self):
        self.throw=random.randrange(3)
        self.key=key[self.throw]

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#81381

On 11/23/2014 10:54 AM, Seymore4Head wrote:
> On Sun, 23 Nov 2014 10:16:28 -0500, Dave Angel <davea@davea.name>
> wrote:
>
>> On 11/23/2014 05:52 AM, Seymore4Head wrote:
>>> On Sun, 23 Nov 2014 17:00:08 +1100, Chris Angelico <rosuav@gmail.com>
>>> wrote:
>>>
>>>>
>>>> 1) Python's namespacing rules mean that 'key' is a part of the RPS
>>>> class, and can be referred to as 'self.key' or as 'RPS.key'
>>>> 2) Use of 'self.key' for the textual form of the throw is shadowing
>>>> the first of those reference names (but it's a poor name anyway)
>>>> 3) A list would work just as well as a dictionary here, since your
>>>> indices are sequential and start from zero
>>>> 4) There's another function in the random module which can do both of
>>>> your steps at once.
>>>>
>>>> Thank you for helping us help you help us all!
>>>>
>>>> ChrisA
>>>
>>> I wish I could explain my problems so precisely.  I will try to do
>>> better in the future.
>>> Thanks
>>>
>>> I will also try this using a list instead of a dictionary.
>>>
>>
>> And please avoid the shadowing.  It's confusing whenever the same name
>> is used for a class attribute and an instance attribute of the same
>> class.  it can be useful for defaults and such, but not here.
>>
>>   class RPS:
>>       KEY_TABLE={0:"rock", 1:"paper",2:"scissors"};
>>    or
>>       KEY_TABLE= ("rock", "paper", "scissors")
>>       def __init__(self):
>>           self.throw=random.randrange(3)
>>           self.key=RPS.KEY_TABLE[self.throw]
>>
>> Note I also capitalized the tuple name, which is a convention saying we
>> don't intend to modify it.
>
> I just learned by trial and error if I moved "key" out of the class, I
> could still use it in the class without having to give it a RPS
> extension.

It's not an extension, it's a namespace qualifier.  That's a good thing, 
to constrain a particular name to as narrow a scope as possible.  In 
other words, instead of making it a global variable, put it in the 
namespace that gives it meaning.

>
> I also changed it to a list and it works fine.
>
> Thanks
>
> key =["rock", "paper", "scissors"]
> class RPS:
>      def __init__(self):
>          self.throw=random.randrange(3)
>          self.key=key[self.throw]
>

But it belongs in the class, doesn't it?  If other code wants to use it, 
it'd be better if all references were of the form  RPS.KEY_TABLE.  And 
it should be a tuple, not a list, as you're not planning to change it.



-- 
DaveA

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#81388

On Sun, 23 Nov 2014 11:14:34 -0500, Dave Angel <davea@davea.name>
wrote:

>On 11/23/2014 10:54 AM, Seymore4Head wrote:
>> On Sun, 23 Nov 2014 10:16:28 -0500, Dave Angel <davea@davea.name>
>> wrote:
>>
>>> On 11/23/2014 05:52 AM, Seymore4Head wrote:
>>>> On Sun, 23 Nov 2014 17:00:08 +1100, Chris Angelico <rosuav@gmail.com>
>>>> wrote:
>>>>
>>>>>
>>>>> 1) Python's namespacing rules mean that 'key' is a part of the RPS
>>>>> class, and can be referred to as 'self.key' or as 'RPS.key'
>>>>> 2) Use of 'self.key' for the textual form of the throw is shadowing
>>>>> the first of those reference names (but it's a poor name anyway)
>>>>> 3) A list would work just as well as a dictionary here, since your
>>>>> indices are sequential and start from zero
>>>>> 4) There's another function in the random module which can do both of
>>>>> your steps at once.
>>>>>
>>>>> Thank you for helping us help you help us all!
>>>>>
>>>>> ChrisA
>>>>
>>>> I wish I could explain my problems so precisely.  I will try to do
>>>> better in the future.
>>>> Thanks
>>>>
>>>> I will also try this using a list instead of a dictionary.
>>>>
>>>
>>> And please avoid the shadowing.  It's confusing whenever the same name
>>> is used for a class attribute and an instance attribute of the same
>>> class.  it can be useful for defaults and such, but not here.
>>>
>>>   class RPS:
>>>       KEY_TABLE={0:"rock", 1:"paper",2:"scissors"};
>>>    or
>>>       KEY_TABLE= ("rock", "paper", "scissors")
>>>       def __init__(self):
>>>           self.throw=random.randrange(3)
>>>           self.key=RPS.KEY_TABLE[self.throw]
>>>
>>> Note I also capitalized the tuple name, which is a convention saying we
>>> don't intend to modify it.
>>
>> I just learned by trial and error if I moved "key" out of the class, I
>> could still use it in the class without having to give it a RPS
>> extension.
>
>It's not an extension, it's a namespace qualifier.  That's a good thing, 
>to constrain a particular name to as narrow a scope as possible.  In 
>other words, instead of making it a global variable, put it in the 
>namespace that gives it meaning.
>
>>
>> I also changed it to a list and it works fine.
>>
>> Thanks
>>
>> key =["rock", "paper", "scissors"]
>> class RPS:
>>      def __init__(self):
>>          self.throw=random.randrange(3)
>>          self.key=key[self.throw]
>>
>
>But it belongs in the class, doesn't it?  If other code wants to use it, 
>it'd be better if all references were of the form  RPS.KEY_TABLE.  And 
>it should be a tuple, not a list, as you're not planning to change it.

Like I have said, most of the stuff I am doing is still trial and
error.  Having to specify RPS to use it inside the class seemed wrong
to me.

I haven't read enough about classes yet to know what the correct way
is yet.

I will leave it in.

Thanks

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#81389

On Mon, Nov 24, 2014 at 3:49 AM, Seymore4Head
<Seymore4Head@hotmail.invalid> wrote:
> Like I have said, most of the stuff I am doing is still trial and
> error.  Having to specify RPS to use it inside the class seemed wrong
> to me.
>
> I haven't read enough about classes yet to know what the correct way
> is yet.

That's because Python doesn't really do the whole "infinitely-nested
scopes" thing that you see in C-like languages. (That kind of scoping
doesn't really work without declared variables, which is completely
against the Python model.) So you have to be a bit more explicit about
where you want to reference things from. What you can do is use 'self'
instead of the class name; that's often the cleanest way to do it.

ChrisA

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#81391

On Sunday, November 23, 2014 10:20:05 PM UTC+5:30, Seymore4Head wrote:
> Like I have said, most of the stuff I am doing is still trial and
> error.  Having to specify RPS to use it inside the class seemed wrong
> to me.

Yes that is natural.
Python is a bit odd in the OO-world in that it prioritizes
"Explicit is better than implicit" over convenience.

Notice that you use self.throw where in most other OOP languages
you would use just throw.

Since the whole point of making 'key' (the table) a class variable
as against an instance variable is that it is not attached to 
self.
So where is it attached?
Answer follows from "Explicit is better than implicit"

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#81422

On Sun, 23 Nov 2014 09:02:57 -0800, Rustom Mody wrote:

> Python is a bit odd in the OO-world in that it prioritizes "Explicit is
> better than implicit" over convenience.
> 
> Notice that you use self.throw where in most other OOP languages you
> would use just throw.

I don't think that is correct. I think that most OOP languages are like 
Python, and use a special variable to reference the current instance:

"self" is used by:
    Smalltalk, Python, Perl, Objective-C, Swift, Ruby, OCAML

"this" is used by:
    C++, C#, Java, D, Javascript, F#, Cobra, PHP, Powershell

"me" is used by:
    ABAP Objects, Visual Basic

"Current" is used by:
    Eiffel


http://en.wikipedia.org/wiki/This_(computer_programming)


http://en.wikipedia.org/wiki/Comparison_of_programming_languages_(object-
oriented_programming)#Special_variables


In some of these languages, the use of "this/self/me" is optional, but 
I'm not aware of *any* OOP language where there is no named reference to 
the current object at all.

In any case, Python is not unusual in this regard.


-- 
Steven

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#81428

On 11/23/2014 11:21 PM, Steven D'Aprano wrote:

> In some of these languages, the use of "this/self/me" is optional, but
> I'm not aware of *any* OOP language where there is no named reference to
> the current object at all.
>

The case I found astounding in C++ was in the initializer list where the 
line

     value:value

would assume that the first one was  this->value, and the second was a 
local named value (usually an argument to the constructor).


-- 
DaveA

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#81429

On Mon, Nov 24, 2014 at 3:21 PM, Steven D'Aprano <steve@pearwood.info> wrote:
> On Sun, 23 Nov 2014 09:02:57 -0800, Rustom Mody wrote:
>
>> Python is a bit odd in the OO-world in that it prioritizes "Explicit is
>> better than implicit" over convenience.
>>
>> Notice that you use self.throw where in most other OOP languages you
>> would use just throw.
>
> I don't think that is correct. I think that most OOP languages are like
> Python, and use a special variable to reference the current instance:
>
> In some of these languages, the use of "this/self/me" is optional, but
> I'm not aware of *any* OOP language where there is no named reference to
> the current object at all.

I believe his point is that Python, unlike every other language he can
think of, requires "self.x" instead of just "x". Every language needs
a way to say "current object", but not every language needs you to say
that for every member reference. C++, Pike, and Java let you
short-hand that. (They're all deriving from the same syntactic style
anyway.) JavaScript doesn't, I believe, although its variable scoping
rules are some of the most insane I've ever met, so there might be a
way to shortcut it. If your experience of OO is mainly from C++/Java
family languages, then yes, Python will seem odd.

ChrisA

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