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list Integer indexing dies??

 
 
Ishwor
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      12-23-2004
Hi all. Look at this snippet of code.

>>> l = ['a','b','c','d']
>>> l

['a', 'b', 'c', 'd']
>>> l[0][0][0]

'a'
It prints the value 'a'. Fine so far
l[0] ---> 'a' .
l[0][0]---> 'a'[0] --> 'a'.
l[0][0][0] ---> 'a'[0][0] --> 'a'[0] --> 'a'

Now why doesnt this list which holds integer seem to work??

>>> l = [1,2,3]
>>> l[0]

1
>>> l[0][0]


Traceback (most recent call last):
File "<pyshell#244>", line 1, in -toplevel-
l[0][0]
TypeError: unsubscriptable object
>>> l[0]

1
>>> 1[0]


Traceback (most recent call last):
File "<pyshell#246>", line 1, in -toplevel-
1[0]
TypeError: unsubscriptable object
>>>


The compiler reports unsubscriptable object ?? confused , dazzled i am ???!!??
The same list now holds integer instead of strings and l[0][0][0]
which worked fine earlier on strings doesn't seem to work on
integers???
Any help is greatly appreciated.



--
cheers,
Ishwor Gurung
 
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Antoon Pardon
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      12-23-2004
Op 2004-12-23, Ishwor schreef <(E-Mail Removed)>:
> Hi all. Look at this snippet of code.
>
>>>> l = ['a','b','c','d']
>>>> l

> ['a', 'b', 'c', 'd']
>>>> l[0][0][0]

> 'a'
> It prints the value 'a'. Fine so far
> l[0] ---> 'a' .
> l[0][0]---> 'a'[0] --> 'a'.
> l[0][0][0] ---> 'a'[0][0] --> 'a'[0] --> 'a'
>
> Now why doesnt this list which holds integer seem to work??


Because this only works with strings.

String is the only object in python which has an implied
equivallence between an element and a squence of one.

So one character is a string and a string is a sequence
of characters.

So 'a'[0] is again 'a' which can again be indexed by
0 as many times as you want.


I think python would have been more consistent if
strings would have been tuples of chars and maybe
implied an equivalence between whatever object and
a singleton of that object.

--
Antoon Pardon
 
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Ishwor
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      12-23-2004
On 23 Dec 2004 14:28:37 GMT, Antoon Pardon <(E-Mail Removed)> wrote:
> Op 2004-12-23, Ishwor schreef <(E-Mail Removed)>:
> > Hi all. Look at this snippet of code.
> >
> >>>> l = ['a','b','c','d']
> >>>> l

> > ['a', 'b', 'c', 'd']
> >>>> l[0][0][0]

> > 'a'
> > It prints the value 'a'. Fine so far
> > l[0] ---> 'a' .
> > l[0][0]---> 'a'[0] --> 'a'.
> > l[0][0][0] ---> 'a'[0][0] --> 'a'[0] --> 'a'
> >
> > Now why doesnt this list which holds integer seem to work??

>
> Because this only works with strings.
>
> String is the only object in python which has an implied
> equivallence between an element and a squence of one.
>
> So one character is a string and a string is a sequence
> of characters.
>
> So 'a'[0] is again 'a' which can again be indexed by
> 0 as many times as you want.


gotcha. But shouldn't this be valid too??
>>> 123232[0]

in which basically python can infer from the object type and print out
1 instead of coughing up those errors? My experience as a learner here
is that there should be some automagics & say like "okay you want to
do indexing on integers ( context dependent); i'll give you the index
of 0th position in that integer" ???


[snip]

Thanks Antoon.
--
cheers,
Ishwor Gurung
 
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Antoon Pardon
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      12-23-2004
Op 2004-12-23, Ishwor schreef <(E-Mail Removed)>:
> On 23 Dec 2004 14:28:37 GMT, Antoon Pardon <(E-Mail Removed)> wrote:
>> Op 2004-12-23, Ishwor schreef <(E-Mail Removed)>:
>> > Hi all. Look at this snippet of code.
>> >
>> >>>> l = ['a','b','c','d']
>> >>>> l
>> > ['a', 'b', 'c', 'd']
>> >>>> l[0][0][0]
>> > 'a'
>> > It prints the value 'a'. Fine so far
>> > l[0] ---> 'a' .
>> > l[0][0]---> 'a'[0] --> 'a'.
>> > l[0][0][0] ---> 'a'[0][0] --> 'a'[0] --> 'a'
>> >
>> > Now why doesnt this list which holds integer seem to work??

>>
>> Because this only works with strings.
>>
>> String is the only object in python which has an implied
>> equivallence between an element and a squence of one.
>>
>> So one character is a string and a string is a sequence
>> of characters.
>>
>> So 'a'[0] is again 'a' which can again be indexed by
>> 0 as many times as you want.

>
> gotcha. But shouldn't this be valid too??
>>>> 123232[0]


Well if it should become valid, it should just return 123232 IMO.

> in which basically python can infer from the object type and print out
> 1 instead of coughing up those errors?


Why do you feel it should cough up 1?

Suppose I write a number in octal notation.

What should 035[0] cough up? Be carefull it should
cough up the same as 29[0].

> My experience as a learner here
> is that there should be some automagics & say like "okay you want to
> do indexing on integers ( context dependent); i'll give you the index
> of 0th position in that integer" ???


Integers have no position. The position we think of in integers is an
artefact of our notational system. Even then if we would simply defer
to decimal notation there is still a problem. You see there are a
number of arguments that would make 123232[0] cough up 2. Because
by starting indexing from the back we get a nice correspondence between
the index of the number and the power of 10 it represents.

--
Antoon Pardon
 
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Ishwor
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      12-23-2004
On 23 Dec 2004 15:05:20 GMT, Antoon Pardon <(E-Mail Removed)> wrote:
> Op 2004-12-23, Ishwor schreef <(E-Mail Removed)>:
> > On 23 Dec 2004 14:28:37 GMT, Antoon Pardon <(E-Mail Removed)> wrote:
> >> Op 2004-12-23, Ishwor schreef <(E-Mail Removed)>:
> >> > Hi all. Look at this snippet of code.
> >> >
> >> >>>> l = ['a','b','c','d']
> >> >>>> l
> >> > ['a', 'b', 'c', 'd']
> >> >>>> l[0][0][0]
> >> > 'a'
> >> > It prints the value 'a'. Fine so far
> >> > l[0] ---> 'a' .
> >> > l[0][0]---> 'a'[0] --> 'a'.
> >> > l[0][0][0] ---> 'a'[0][0] --> 'a'[0] --> 'a'
> >> >
> >> > Now why doesnt this list which holds integer seem to work??
> >>
> >> Because this only works with strings.
> >>
> >> String is the only object in python which has an implied
> >> equivallence between an element and a squence of one.
> >>
> >> So one character is a string and a string is a sequence
> >> of characters.
> >>
> >> So 'a'[0] is again 'a' which can again be indexed by
> >> 0 as many times as you want.

> >
> > gotcha. But shouldn't this be valid too??
> >>>> 123232[0]

>
> Well if it should become valid, it should just return 123232 IMO.
>

Im not sure i understand u but what i meant was that
>>> 123 + 2

125 # nice n good

now it would be nice if integer could also be *subscripted* too
>>> 123[0] + 2

3
But as i said in earlier post said, i'll stick with import this's
#2 by Tim Peters. Its better to leave these design issues with other
**senior pythoneers**.


> > in which basically python can infer from the object type and print out
> > 1 instead of coughing up those errors?

>
> Why do you feel it should cough up 1?
>



>>>123232[0] #hypothetical 0th position in the integer.

1


> Suppose I write a number in octal notation.
>
> What should 035[0] cough up? Be carefull it should


>>>035[0]

3 # my own opinion.

> cough up the same as 29[0].


>>>29[0]

2 #again my own opinion


[snip]

> by starting indexing from the back we get a nice correspondence between
> the index of the number and the power of 10 it represents.
>
> --
> Antoon Pardon
> --
> http://mail.python.org/mailman/listinfo/python-list
>


As in my view if python could treat object in context sensitive
manner, it would be better world but its just my own beginners
opinion.
Happy hunting with Python.

--
cheers,
Ishwor Gurung
 
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Lonnie Princehouse
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      12-23-2004
> gotcha. But shouldn't this be valid too??
> >>> 123232[0]


No, it shouldn't be valid. It makes the implicit assumption that you
want the base 10 digit, which isn't really a good assumption to make in
the world of computers. Programmers are just as likely to want
hexadecimal, and arguments could be made for octal or binary too.
Basically, there's no intuitive meaning for trying to slice an integer.

Also, it seems like it would be very rare that anybody would want to do
this. Most of those cases fall into one of two categories- (1) trying
to display digits of a number in a human readable way, and (2) trying
to do some kind of math.

(1) is better handled by explicitly converting it to a string first,
and
(2) is likely better handled using logarithms.

 
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Stephen Thorne
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      12-23-2004
On Fri, 24 Dec 2004 02:59:40 +1030, Ishwor <(E-Mail Removed)> wrote:

> >>> 123[0] + 2

> 3

TypeError: unsubscriptable object

> > > in which basically python can infer from the object type and print out
> > > 1 instead of coughing up those errors?

> >
> > Why do you feel it should cough up 1?
> >

>
> >>>123232[0] #hypothetical 0th position in the integer.

> 1

TypeError: unsubscriptable object

> > Suppose I write a number in octal notation.
> >
> > What should 035[0] cough up? Be carefull it should

>
> >>>035[0]

> 3 # my own opinion.

TypeError: unsubscriptable object

> > cough up the same as 29[0].

>
> >>>29[0]

> 2 #again my own opinion

TypeError: unsubscriptable object


Just-in-my-own-opinion-ly y'rs

Stephen Thorne
 
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Duncan Booth
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      12-24-2004
Antoon Pardon wrote:

> Suppose I write a number in octal notation.
>
> What should 035[0] cough up? Be carefull it should
> cough up the same as 29[0].
>


given that 035==000000000000000000000000000000000000000000000 035 I say they
should both cough up 0 for any positive index of course.
 
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Mike Meyer
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      12-24-2004
Ishwor <(E-Mail Removed)> writes:

> On 23 Dec 2004 14:28:37 GMT, Antoon Pardon <(E-Mail Removed)> wrote:
> My experience as a learner here is that there should be some
> automagics & say like "okay you want to do indexing on integers (
> context dependent); i'll give you the index of 0th position in that
> integer" ???


Python doesn't do things automagically. The rules for pythonic
behavior include "Explicit is better than implicit" and "In the face
of ambiguity, refuse the tempation to guess." Both of those are
violated by automatic conversions and the like.

<mike
--
Mike Meyer <(E-Mail Removed)> http://www.mired.org/home/mwm/
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.
 
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Ishwor
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      12-24-2004
On Fri, 24 Dec 2004 05:44:50 -0600, Mike Meyer <(E-Mail Removed)> wrote:
> Ishwor <(E-Mail Removed)> writes:
>
> > On 23 Dec 2004 14:28:37 GMT, Antoon Pardon <(E-Mail Removed)> wrote:
> > My experience as a learner here is that there should be some
> > automagics & say like "okay you want to do indexing on integers (
> > context dependent); i'll give you the index of 0th position in that
> > integer" ???

>
> Python doesn't do things automagically. The rules for pythonic
> behavior include "Explicit is better than implicit" and "In the face
> of ambiguity, refuse the tempation to guess." Both of those are
> violated by automatic conversions and the like.
>


Well *shrugs* that was just an opionion though a bad one from a
beginner ... No hard feeling pythoner friends. and Merry
Christmas to you all
Then gingerbread is ready at
http://www.mediatinker.com/blog/archives/008798.html


[snip]

--
cheers,
Ishwor Gurung
 
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