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Practice question

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  Practice question Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-05 19:02 -0400
    Re: Practice question Roy Smith <roy@panix.com> - 2014-10-05 19:06 -0400
    Re: Practice question Ned Batchelder <ned@nedbatchelder.com> - 2014-10-05 19:14 -0400
      Re: Practice question Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-05 20:07 -0400
        Re: Practice question Ned Batchelder <ned@nedbatchelder.com> - 2014-10-05 21:25 -0400
        Re: Practice question Steven D'Aprano <steve@pearwood.info> - 2014-10-07 08:41 +0000
    Re: Practice question Skip Montanaro <skip.montanaro@gmail.com> - 2014-10-05 18:33 -0500
      Re: Practice question Rustom Mody <rustompmody@gmail.com> - 2014-10-05 19:47 -0700
        Re: Practice question Skip Montanaro <skip.montanaro@gmail.com> - 2014-10-06 08:04 -0500
          Re: Practice question Rustom Mody <rustompmody@gmail.com> - 2014-10-06 09:23 -0700
            Re: Practice question Chris Angelico <rosuav@gmail.com> - 2014-10-07 03:52 +1100
              Re: Practice question Rustom Mody <rustompmody@gmail.com> - 2014-10-06 10:05 -0700
                Re: Practice question Chris Angelico <rosuav@gmail.com> - 2014-10-07 04:13 +1100
                Re: Practice question Steven D'Aprano <steve@pearwood.info> - 2014-10-06 20:49 +0000
                  Re: Practice question "Redge @ Versalytics.com" <versalytics@gmail.com> - 2014-10-06 20:54 -0400
                  Re: Practice question Rustom Mody <rustompmody@gmail.com> - 2014-10-08 09:14 -0700
                    Re: Practice question Chris Angelico <rosuav@gmail.com> - 2014-10-09 03:23 +1100
                    Re: Practice question Skip Montanaro <skip.montanaro@gmail.com> - 2014-10-08 11:27 -0500
                      Re: Practice question Rustom Mody <rustompmody@gmail.com> - 2014-10-08 09:41 -0700
    Re: Practice question Terry Reedy <tjreedy@udel.edu> - 2014-10-05 19:47 -0400
      Re: Practice question Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-05 20:18 -0400
        Re: Practice question Steven D'Aprano <steve@pearwood.info> - 2014-10-07 08:48 +0000
          Re: Practice question C Smith <illusiontechniques@gmail.com> - 2014-10-07 05:43 -0700
    Re: Practice question C Smith <illusiontechniques@gmail.com> - 2014-10-05 16:24 -0700
    Re: Practice question Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-07 01:46 +0000
      Re: Practice question Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-06 22:06 -0400
        Re: Practice question alister <alister.nospam.ware@ntlworld.com> - 2014-10-09 15:28 +0000

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#78732

On Sun, 05 Oct 2014 19:47:40 -0400, Terry Reedy <tjreedy@udel.edu>
wrote:

>On 10/5/2014 7:02 PM, Seymore4Head wrote:
>> For the record, I don't want a hint.  I want the answer.
>> I see a practice question is similar to this.
>> 15 <= x < 30  And it wants a similar expression that is equivalent.
>> So the right answer is 15<= x or x <30
>> but one of the other answers is
>> not (15<= x and x <30)
>>
>> But it says.....remember you can try this out in the Python shell.
>> How?
>
>For instance,
>for x in (10, 20, 30, 40):
>     print((15 <= x < 30) == (15<= x and x <30))

I think I get it now.  You are using a sample of answers.  So you
could actually just run through them all.  (I haven't tried this yet)

for x in range(lo,hi)
     print((15 <= x < 30) == (15<= x and x <30))

Thanks

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#78795

On Sun, 05 Oct 2014 20:18:13 -0400, Seymore4Head wrote:

> I think I get it now.  You are using a sample of answers.  So you could
> actually just run through them all.  (I haven't tried this yet)
> 
> for x in range(lo,hi)
>      print((15 <= x < 30) == (15<= x and x <30))

Yes, except using print is probably not the best idea, since you might 
have dozens of True True True True ... printed, one per line, and if you 
blink the odd False might have scrolled off screen before you notice.

With two numbers, 15 and 30, all you really need is five test cases:

- a number lower than the smaller of the two numbers (say, 7);
- a number equal to the smaller of the two numbers (that is, 15);
- a number between the two numbers (say, 21);
- a number equal to the larger of the two numbers (that is, 30);
- a number higher than the larger of the two numbers (say, 999);


The exact numbers don't matter, so long as you test all five cases. And 
rather than printing True True True... let's use assert instead:


for x in (7, 15, 21, 30, 999):
    assert (15 <= x < 30) == (15<= x and x <30)


If the two cases are equal, assert will do nothing. But if they are 
unequal, assert will raise an exception and stop, and you know that the 
two cases are not equivalent and can go on to the next possibility.


-- 
Steven

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#78798

Steven D'Aprano wrote:
>>With two numbers, 15 and 30, all you really need is five test cases:

My solution assumed integers also, but after I posted it, I thought:
"What about floating points?"

On Tue, Oct 7, 2014 at 1:48 AM, Steven D'Aprano <steve@pearwood.info> wrote:
> On Sun, 05 Oct 2014 20:18:13 -0400, Seymore4Head wrote:
>
>> I think I get it now.  You are using a sample of answers.  So you could
>> actually just run through them all.  (I haven't tried this yet)
>>
>> for x in range(lo,hi)
>>      print((15 <= x < 30) == (15<= x and x <30))
>
> Yes, except using print is probably not the best idea, since you might
> have dozens of True True True True ... printed, one per line, and if you
> blink the odd False might have scrolled off screen before you notice.
>
> With two numbers, 15 and 30, all you really need is five test cases:
>
> - a number lower than the smaller of the two numbers (say, 7);
> - a number equal to the smaller of the two numbers (that is, 15);
> - a number between the two numbers (say, 21);
> - a number equal to the larger of the two numbers (that is, 30);
> - a number higher than the larger of the two numbers (say, 999);
>
>
> The exact numbers don't matter, so long as you test all five cases. And
> rather than printing True True True... let's use assert instead:
>
>
> for x in (7, 15, 21, 30, 999):
>     assert (15 <= x < 30) == (15<= x and x <30)
>
>
> If the two cases are equal, assert will do nothing. But if they are
> unequal, assert will raise an exception and stop, and you know that the
> two cases are not equivalent and can go on to the next possibility.
>
>
> --
> Steven
> --
> https://mail.python.org/mailman/listinfo/python-list

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#78739

14<x<=29

On Sun, Oct 5, 2014 at 4:14 PM, Ned Batchelder <ned@nedbatchelder.com> wrote:
> On 10/5/14 7:02 PM, Seymore4Head wrote:
>>
>> For the record, I don't want a hint.  I want the answer.
>> I see a practice question is similar to this.
>> 15 <= x < 30  And it wants a similar expression that is equivalent.
>> So the right answer is 15<= x or x <30
>
>
> No, "15 <= x < 30" is equivalent to "15 <= x and x < 30".
>
>> but one of the other answers is
>> not (15<= x and x <30)
>
>
> You are speaking ambiguously.  Which did you mean:
> a) one of the other answers isn't "15 <= x and x < 30", or:
> b) one of the other answers is "not (15 <= x and x < 30)" ?
>
> --
> Ned Batchelder, http://nedbatchelder.com
>
> --
> https://mail.python.org/mailman/listinfo/python-list

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#78786

On Sun, 05 Oct 2014 19:02:31 -0400, Seymore4Head wrote:

> For the record, I don't want a hint.  I want the answer.
> I see a practice question is similar to this.
> 15 <= x < 30  And it wants a similar expression that is equivalent.

I think part of the problem here is that you don't understand the 
expression.

The expression:

15 <= x < 30

contains two conditions:

15 <= x

x < 30

For the whole expression to be true, both conditions must be true, hence 
the equivalence is:

(15 <= x) and (x < 30)

to test this in python command line, see if the two different expressions 
give the same result for a suitable range of values of x:

for x in range(50):
    if not (15 <= x < 30) == ((15 <= x) and (x < 30)):
        print "discrepancy"

or

for x in range(50):
    if (15 <= x < 30) == ((15 <= x) and (x < 30)):
        print "ok"

-- 
Denis McMahon, denismfmcmahon@gmail.com

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#78788

On Tue, 7 Oct 2014 01:46:37 +0000 (UTC), Denis McMahon
<denismfmcmahon@gmail.com> wrote:

>On Sun, 05 Oct 2014 19:02:31 -0400, Seymore4Head wrote:
>
>> For the record, I don't want a hint.  I want the answer.
>> I see a practice question is similar to this.
>> 15 <= x < 30  And it wants a similar expression that is equivalent.
>
>I think part of the problem here is that you don't understand the 
>expression.
>
>The expression:
>
>15 <= x < 30
>
>contains two conditions:
>
>15 <= x
>
>x < 30
>
>For the whole expression to be true, both conditions must be true, hence 
>the equivalence is:
>
>(15 <= x) and (x < 30)
>
>to test this in python command line, see if the two different expressions 
>give the same result for a suitable range of values of x:
>
>for x in range(50):
>    if not (15 <= x < 30) == ((15 <= x) and (x < 30)):
>        print "discrepancy"
>
>or
>
>for x in range(50):
>    if (15 <= x < 30) == ((15 <= x) and (x < 30)):
>        print "ok"

All of the practice questions up to this question had 4 answers.  With
each question you could verify the correct answers by just copy and
pasting each choice into Python.

So when the instructions said I could verify this with Python I
assumed there might be some way to test if the question was == to each
answer.

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#78897

On Mon, 06 Oct 2014 22:06:09 -0400, Seymore4Head wrote:

> On Tue, 7 Oct 2014 01:46:37 +0000 (UTC), Denis McMahon
> <denismfmcmahon@gmail.com> wrote:
> 
>>On Sun, 05 Oct 2014 19:02:31 -0400, Seymore4Head wrote:
>>
>>> For the record, I don't want a hint.  I want the answer.
>>> I see a practice question is similar to this.
>>> 15 <= x < 30  And it wants a similar expression that is equivalent.
>>
>>I think part of the problem here is that you don't understand the
>>expression.
>>
>>The expression:
>>
>>15 <= x < 30
>>
>>contains two conditions:
>>
>>15 <= x
>>
>>x < 30
>>
>>For the whole expression to be true, both conditions must be true, hence
>>the equivalence is:
>>
>>(15 <= x) and (x < 30)
>>
>>to test this in python command line, see if the two different
>>expressions give the same result for a suitable range of values of x:
>>
>>for x in range(50):
>>    if not (15 <= x < 30) == ((15 <= x) and (x < 30)):
>>        print "discrepancy"
>>
>>or
>>
>>for x in range(50):
>>    if (15 <= x < 30) == ((15 <= x) and (x < 30)):
>>        print "ok"
> 
> All of the practice questions up to this question had 4 answers.  With
> each question you could verify the correct answers by just copy and
> pasting each choice into Python.
> 
> So when the instructions said I could verify this with Python I assumed
> there might be some way to test if the question was == to each answer.

no 
you need to type in each snippet of code & see if they give the same 
result when run.




-- 
In every non-trivial program there is at least one bug.

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