The following is part of the explanation on slices in the
tutorial:
The best way to remember how slices work is to think of the indices as
pointing between characters, with the left edge of the first character
numbered 0. Then the right edge of the last character of a string of n
characters has index n, for example:
+---+---+---+---+---+
| H | e | l | p | A |
+---+---+---+---+---+
0 1 2 3 4 5
-5 -4 -3 -2 -1
This is all very well with a simple slice like:
"HelpA"[2:4] = "lp"
But it give the wrong idea when using the following extended slice:
"HelpA"[4:2:-1] = "Ap"
So this doesn't result in the reverse of the previous expression while
the explanation above suggest it does.
So I suggest to drop this.
--
Antoon Pardon
31  1725 
Antoon Pardon wrote:
The following is part of the explanation on slices in the
tutorial:
The best way to remember how slices work is to think of the indices as
pointing between characters, with the left edge of the first character
numbered 0. Then the right edge of the last character of a string of n
characters has index n, for example:
+---+---+---+---+---+
| H | e | l | p | A |
+---+---+---+---+---+
0 1 2 3 4 5
-5 -4 -3 -2 -1
This is all very well with a simple slice like:
"HelpA"[2:4] = "lp"
But it give the wrong idea when using the following extended slice:
"HelpA"[4:2:-1] = "Ap"
So this doesn't result in the reverse of the previous expression while
the explanation above suggest it does.
Clearly I understand that differently:
>>"HelpA"[-2:-4:-1]
'pl'
--
Regards,
Rob
On 2007-04-23, Rob Wolfe <rw@smsnet.plwr ote:
>
Antoon Pardon wrote:
>The following is part of the explanation on slices in the
tutorial:
The best way to remember how slices work is to think of the indices as
pointing between characters, with the left edge of the first character
numbered 0. Then the right edge of the last character of a string of n
characters has index n, for example:
+---+---+---+---+---+
| H | e | l | p | A |
+---+---+---+---+---+
0 1 2 3 4 5
-5 -4 -3 -2 -1
This is all very well with a simple slice like:
"HelpA"[2:4] = "lp"
But it give the wrong idea when using the following extended slice:
"HelpA"[4:2:-1] = "Ap"
So this doesn't result in the reverse of the previous expression while
the explanation above suggest it does.
Clearly I understand that differently:
>>>"HelpA"[-2:-4:-1]
'pl'
This is not about what you understand. This is about what the tutorial
seems to suggest here and whether or not that corresponds with how
python actually works.
Read the explanation and look at the picture. The -2 is to the right
of "l" the -4 is to the left of "e". So the picture IMO suggests
that "HelpA"[-2:-4:-1] would result in "le"
--
Antoon Pardon
On Apr 23, 2007, at 7:38 AM, Antoon Pardon wrote:
The following is part of the explanation on slices in the
tutorial:
The best way to remember how slices work is to think of the indices as
pointing between characters, with the left edge of the first character
numbered 0. Then the right edge of the last character of a string of n
characters has index n, for example:
+---+---+---+---+---+
| H | e | l | p | A |
+---+---+---+---+---+
0 1 2 3 4 5
-5 -4 -3 -2 -1
This is all very well with a simple slice like:
"HelpA"[2:4] = "lp"
But it give the wrong idea when using the following extended slice:
"HelpA"[4:2:-1] = "Ap"
So this doesn't result in the reverse of the previous expression while
the explanation above suggest it does.
So I suggest to drop this.
But 'drop' means to let or make (something) fall vertically... :-)
At that point in the tutorial, step values had not been discussed.
Just a bit lower down on the page you'll find a link to 'Sequence
Types' where you'll find an explanation of stepping you'll perhaps
find more satisfactory.
hth,
Michael
---
"Those who don't understand UNIX are condemned to reinvent it,
poorly." --Henry Spencer
On 2007-04-23, Michael Bentley <mi*****@jedimi ndworks.comwrot e:
>
On Apr 23, 2007, at 7:38 AM, Antoon Pardon wrote:
>The following is part of the explanation on slices in the
tutorial:
The best way to remember how slices work is to think of the indices as
pointing between characters, with the left edge of the first character
numbered 0. Then the right edge of the last character of a string of n
characters has index n, for example:
+---+---+---+---+---+
| H | e | l | p | A |
+---+---+---+---+---+
0 1 2 3 4 5
-5 -4 -3 -2 -1
This is all very well with a simple slice like:
"HelpA"[2:4] = "lp"
But it give the wrong idea when using the following extended slice:
"HelpA"[4:2:-1] = "Ap"
So this doesn't result in the reverse of the previous expression while
the explanation above suggest it does.
So I suggest to drop this.
But 'drop' means to let or make (something) fall vertically... :-)
At that point in the tutorial, step values had not been discussed.
Just a bit lower down on the page you'll find a link to 'Sequence
Types' where you'll find an explanation of stepping you'll perhaps
find more satisfactory.
That is very well posible. The question: Even if we get a good
explanation later, do we want an explanation here that can cause
confusion. These things are not just read and then discarded.
Someone can already have read the whole tutorial and then come
back to this place. So at that point he knows about stepping
when he is reading this.
I suspect that if you give this explanation to someone and explain
that there is also a step parameter, chances are he will answer
correctly if you ask him, what he thinks the following will result
in:
"This is an example line"[12:19:2]
If you ask him what the following will result in:
"This is an example line"[19:12:-1]
Chances are he will give the wrong answer.
On Apr 24, 2007, at 1:39 AM, Antoon Pardon wrote:
On 2007-04-23, Michael Bentley <mi*****@jedimi ndworks.comwrot e:
>>
On Apr 23, 2007, at 7:38 AM, Antoon Pardon wrote:
>>The following is part of the explanation on slices in the
tutorial:
The best way to remember how slices work is to think of the
indices as
pointing between characters, with the left edge of the first
character
numbered 0. Then the right edge of the last character of a string
of n
characters has index n, for example:
+---+---+---+---+---+
| H | e | l | p | A |
+---+---+---+---+---+
0 1 2 3 4 5
-5 -4 -3 -2 -1
This is all very well with a simple slice like:
"HelpA"[2:4] = "lp"
But it give the wrong idea when using the following extended slice:
"HelpA"[4:2:-1] = "Ap"
So this doesn't result in the reverse of the previous expression
while
the explanation above suggest it does.
So I suggest to drop this.
But 'drop' means to let or make (something) fall vertically... :-)
At that point in the tutorial, step values had not been discussed.
Just a bit lower down on the page you'll find a link to 'Sequence
Types' where you'll find an explanation of stepping you'll perhaps
find more satisfactory.
That is very well posible. The question: Even if we get a good
explanation later, do we want an explanation here that can cause
confusion. These things are not just read and then discarded.
Someone can already have read the whole tutorial and then come
back to this place. So at that point he knows about stepping
when he is reading this.
I suspect that if you give this explanation to someone and explain
that there is also a step parameter, chances are he will answer
correctly if you ask him, what he thinks the following will result
in:
"This is an example line"[12:19:2]
If you ask him what the following will result in:
"This is an example line"[19:12:-1]
Chances are he will give the wrong answer.
To be honest, bro -- I'd expect him to have enough intelligence to
experiment for a second and figure it out. This isn't rocket science
-- you can plainly see what's happening -- so learn it and move on.
Or better yet, quietly submit a patch...
On 2007-04-24, Michael Bentley <mi*****@jedimi ndworks.comwrot e:
>
On Apr 24, 2007, at 1:39 AM, Antoon Pardon wrote:
>I suspect that if you give this explanation to someone and explain
that there is also a step parameter, chances are he will answer
correctly if you ask him, what he thinks the following will result
in:
"This is an example line"[12:19:2]
If you ask him what the following will result in:
"This is an example line"[19:12:-1]
Chances are he will give the wrong answer.
To be honest, bro -- I'd expect him to have enough intelligence to
experiment for a second and figure it out. This isn't rocket science
-- you can plainly see what's happening -- so learn it and move on.
I don't think that the possibility to experiment and see for oneself
is a good reason to keep a possible confusing explanation in a tutorial.
Or better yet, quietly submit a patch...
Why should I? If the reactions would have been one of agreement that
this is confusing and that the explanation should be changed, I would
have considered submitting a patch.
But most people that reacted seem to defend the current text in some
way or another. So if most people seem to feel there is no need for
a change why should I then submit a patch?
--
Antoon Pardon
On Apr 24, 2007, at 4:47 AM, Antoon Pardon wrote:
On 2007-04-24, Michael Bentley <mi*****@jedimi ndworks.comwrot e:
>>
On Apr 24, 2007, at 1:39 AM, Antoon Pardon wrote:
>>I suspect that if you give this explanation to someone and explain
that there is also a step parameter, chances are he will answer
correctly if you ask him, what he thinks the following will result
in:
"This is an example line"[12:19:2]
If you ask him what the following will result in:
"This is an example line"[19:12:-1]
Chances are he will give the wrong answer.
To be honest, bro -- I'd expect him to have enough intelligence to
experiment for a second and figure it out. This isn't rocket science
-- you can plainly see what's happening -- so learn it and move
on.
I don't think that the possibility to experiment and see for oneself
is a good reason to keep a possible confusing explanation in a
tutorial.
It's only potentially confusing if you already know more than has
been presented and are in fact, *experimenting* with techniques that
have yet to be presented.
>Or better yet, quietly submit a patch...
Why should I? If the reactions would have been one of agreement that
this is confusing and that the explanation should be changed, I would
have considered submitting a patch.
But most people that reacted seem to defend the current text in some
way or another. So if most people seem to feel there is no need for
a change why should I then submit a patch?
.... or even continue the thread?
On 2007-04-24, Michael Bentley <mi*****@jedimi ndworks.comwrot e:
>
On Apr 24, 2007, at 4:47 AM, Antoon Pardon wrote:
>On 2007-04-24, Michael Bentley <mi*****@jedimi ndworks.comwrot e:
>>>
On Apr 24, 2007, at 1:39 AM, Antoon Pardon wrote:
I suspect that if you give this explanation to someone and explain
that there is also a step parameter, chances are he will answer
correctly if you ask him, what he thinks the following will result
in:
"This is an example line"[12:19:2]
If you ask him what the following will result in:
"This is an example line"[19:12:-1]
Chances are he will give the wrong answer.
To be honest, bro -- I'd expect him to have enough intelligence to
experiment for a second and figure it out. This isn't rocket science
-- you can plainly see what's happening -- so learn it and move
on.
I don't think that the possibility to experiment and see for oneself
is a good reason to keep a possible confusing explanation in a
tutorial.
It's only potentially confusing if you already know more than has
been presented and are in fact, *experimenting* with techniques that
have yet to be presented.
People don't read tutorials in a strictly linear fashion. They can
continue to later subjects and then come back here to see how things
tie together. So the fact that it is only confusing to those who
know more than is already presented doesn't seem a very good reason
to leave it in.
>>Or better yet, quietly submit a patch...
Why should I? If the reactions would have been one of agreement that
this is confusing and that the explanation should be changed, I would
have considered submitting a patch.
But most people that reacted seem to defend the current text in some
way or another. So if most people seem to feel there is no need for
a change why should I then submit a patch?
... or even continue the thread?
It is always interresting to see how far people are willing to go to
defend the status quo.
I bet that if the tutorial was written now, given the possible
confusion, nobody would defend including this section. But now
that it already is in the tutorial it suddenly is worth defending.
--
Antoon Pardon
On Apr 24, 2007, at 6:35 AM, Antoon Pardon wrote:
On 2007-04-24, Michael Bentley <mi*****@jedimi ndworks.comwrot e:
>>
On Apr 24, 2007, at 4:47 AM, Antoon Pardon wrote:
>>On 2007-04-24, Michael Bentley <mi*****@jedimi ndworks.comwrot e:
On Apr 24, 2007, at 1:39 AM, Antoon Pardon wrote:
I suspect that if you give this explanation to someone and explain
that there is also a step parameter, chances are he will answer
correctly if you ask him, what he thinks the following will result
in:
>
>
"This is an example line"[12:19:2]
>
>
>
If you ask him what the following will result in:
>
"This is an example line"[19:12:-1]
>
Chances are he will give the wrong answer.
To be honest, bro -- I'd expect him to have enough intelligence to
experiment for a second and figure it out. This isn't rocket
science
-- you can plainly see what's happening -- so learn it and move
on.
I don't think that the possibility to experiment and see for oneself
is a good reason to keep a possible confusing explanation in a
tutorial.
It's only potentially confusing if you already know more than has
been presented and are in fact, *experimenting* with techniques that
have yet to be presented.
People don't read tutorials in a strictly linear fashion. They can
continue to later subjects and then come back here to see how things
tie together. So the fact that it is only confusing to those who
know more than is already presented doesn't seem a very good reason
to leave it in.
Yet they understand that earlier in the document, there is likely to
be a less complete coverage of a given topic. There is in fact, a
link on that page that includes a more complete coverage of that
topic (which I mentioned to you in an earlier message IIRC).
>
>>>Or better yet, quietly submit a patch...
Why should I? If the reactions would have been one of agreement that
this is confusing and that the explanation should be changed, I
would
have considered submitting a patch.
But most people that reacted seem to defend the current text in some
way or another. So if most people seem to feel there is no need for
a change why should I then submit a patch?
... or even continue the thread?
It is always interresting to see how far people are willing to go to
defend the status quo.
I bet that if the tutorial was written now, given the possible
confusion, nobody would defend including this section. But now
that it already is in the tutorial it suddenly is worth defending.
Submit a patch if you want it changed. I'm sure your valuable
insights will greatly improve the quality of the python documentation. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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