date:20180826



Change by miss-islington :


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Re: Writing a program to illustrate a fractal

On 8/26/18 5:40 PM, Dennis Lee Bieber wrote:
>   But their definition is still confusing as it is formulated with a
> expression as the argument to a().
>
>   Taken literally, it says for n+4 to call a() with an argument of 8 (2n)
> AND to call it with an argument of 7 (2n-1) (returning two values) 

I have seen that sort of notation before for defining sequences (which
is what he was doing). Yes, it is not very useful for actually
implementing a function to compute the values, but if a was stored in an
array it makes some sense, as you make a loop that runs n, and compute
the various elements. The one confusion with how it was defined was that
the recursive definition starts at n=2, but for that value you only
compute the even value, as 2*n-1 = 3 which has already been defined, and
that definition would reference a(0) which hasn't been defined.

This is one reason I presented what I say as the 'normalized' equations
which are what would be more needed to actually compute as a function.

-- 
Richard Damon

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[issue34512] Document platform-specific strftime() behavior for non-ASCII format strings

2018-08-26 Thread Alexey Izbyshev



Change by Alexey Izbyshev :


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[issue34512] Document platform-specific strftime() behavior for non-ASCII format strings

2018-08-26 Thread Alexey Izbyshev


New submission from Alexey Izbyshev :

If a format string contains code points outside of ASCII range, time.strftime() 
can behave in four different ways depending on the platform, the current locale 
and the code points:

* raise a UnicodeEncodeError
* return an empty string
* for surrogates in \uDC80-\uDCFF range, replace them with different code 
points in the output (potentially mangling nearby parts of the output as well)
* round-trip them correctly

Some examples:

* Linux (glibc 2.27):
Python 3.6.4 (default, Jan 03 2018, 13:52:55) [GCC] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import time, locale
>>> locale.getlocale()
('en_US', 'UTF-8')
>>> time.strftime('\x80')
'\x80'
>>> time.strftime('\u044f')
'я' # '\u044f'
>>> time.strftime('\ud800')
'\ud800'
>>> time.strftime('\udcff')
'\udcff'
>>> locale.setlocale(locale.LC_CTYPE, 'C')
'C'
>>> time.strftime('\x80')
'\x80'
>>> time.strftime('\u044f')
'я' # '\u044f'
>>> time.strftime('\ud800')
'\ud800'
>>> time.strftime('\udcff')
'\udcff'

* macOS 10.13.6 and FreeBSD 11.1:
Python 3.7.0 (default, Jul 23 2018, 20:22:55)
[Clang 9.1.0 (clang-902.0.39.2)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import time, locale
>>> locale.getlocale()
('en_US', 'UTF-8')
>>> time.strftime('\x80')
'\x80'
>>> time.strftime('\u044f')
'я' # '\u044f'
>>> time.strftime('\ud800')
''
>>> time.strftime('\udcff')
''
>>> locale.setlocale(locale.LC_CTYPE, 'C')
'C'
>>> time.strftime('\x80')
'\x80'
>>> time.strftime('\u044f')
''
>>> time.strftime('\ud800')
''
>>> time.strftime('\udcff')
''

* Windows 8.1:
Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MSC v.1914 64 bit 
(AMD64)] on win32
>>> import time, locale
>>> locale.getlocale()
(None, None)
>>> time.strftime('\x80')
'\x80'
>>> time.strftime('\u044f')
Traceback (most recent call last):
  File "", line 1, in 
UnicodeEncodeError: 'locale' codec can't encode character '\u044f' in position 
0: encoding error
>>> time.strftime('\ud800')
Traceback (most recent call last):
  File "", line 1, in 
UnicodeEncodeError: 'locale' codec can't encode character '\ud800' in position 
0: encoding error
>>> time.strftime('\udcff')
'y' # '\xff'
>>> locale.setlocale(locale.LC_CTYPE, '')
'Russian_Russia.1251'
>>> time.strftime('\x80')
Traceback (most recent call last):
  File "", line 1, in 
UnicodeEncodeError: 'locale' codec can't encode character '\x80' in position 0: 
encoding error
>>> time.strftime('\u044f')
'я' # '\u044f'
>>> time.strftime('\ud800')
Traceback (most recent call last):
  File "", line 1, in 
UnicodeEncodeError: 'locale' codec can't encode character '\ud800' in position 
0: encoding error
>>> time.strftime('\udcff')
'я' # '\u044f'

The reasons of such differences are the following:
* Reliance on either wcsftime() or strftime() from the C library depending on 
the platform.
* For strftime(), the input is encoded into the charset of the current locale 
with 'surrogateescape' error handler, and the output is decoded back in the 
same way.
* Different handling of code points which are unrepresentable in the charset of 
the current locale by glibc and macOS/FreeBSD.

I suggest to at least document that the format string, despite being an 'str', 
requires special care if it contains non-ASCII code points.

The 'datetime' module docs warn about the locale-dependent output, but only 
with regard to particular format specifiers [1].

I'll submit a draft PR. Suggestions are welcome.

[1] 
https://docs.python.org/3.7/library/datetime.html#strftime-and-strptime-behavior

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messages: 324136
nosy: belopolsky, docs@python, izbyshev, p-ganssle, taleinat
priority: normal
severity: normal
status: open
title: Document platform-specific strftime() behavior for non-ASCII format 
strings
type: enhancement
versions: Python 3.6, Python 3.7, Python 3.8

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[issue34511] I suggest to add documentation about "method" parameter of urllib.request.Request class

2018-08-26 Thread Mariatta Wijaya



Mariatta Wijaya  added the comment:

method is added in Python 3.3. You're referencing documentation of Python 3.2.

The documentation is correct for later Python versions: 
https://docs.python.org/3.7/library/urllib.request.html#urllib.request.Request

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[issue34510] add HTTPConnection.settimeout()

2018-08-26 Thread Benjamin Peterson



Change by Benjamin Peterson :


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title: Add add HTTPConnection.settimeout() -> add HTTPConnection.settimeout()

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[issue34511] I suggest to add documentation about "method" parameter of urllib.request.Request class

2018-08-26 Thread harobed


New submission from harobed :

Hi,

I see "method=None" parameter in urllib.request.Request constructor 
(https://github.com/python/cpython/blob/master/Lib/urllib/request.py#L327) but 
I don't see "method" parameter in documentation: 
https://docs.python.org/3.2/library/urllib.request.html#urllib.request.Request

I suggest to add documentation about "method".

Best regards,
Stéphane

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type: enhancement
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Re: Generating a specific list of intsgers

On 8/26/18 4:20 PM, Musatov wrote:
> My understanding is this: there are an infinite number of n's that are not 
> multiples of three, and yet will always be divisible by at least one of 22 
> primes for all values of k.
>
> i.e. certain n values make the equation produce only composite numbers for 
> all values of k.

But that isn't enough to make the function computable. While we may be
able to have some short cut rules to tell us that for SOME n, the answer
is 0, unless we can answer that question for ALL n, we can't be sure to
compute the answer. If we could compute an upper limit for k given n,
then we could do the computation, but we need to have some rule to stop,
or there may be some values of n that we will loop forever on.

As has been said, this problem is still in the domain of needing some
math to give us the rule to compute with.

-- 
Richard Damon

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Re: Generating a specific list of intsgers

On Sunday, August 26, 2018 at 3:21:08 PM UTC-5, Musatov wrote:
> On Sunday, August 26, 2018 at 3:07:41 PM UTC-5, Oscar Benjamin wrote:
> > On Sun, 26 Aug 2018 at 20:32, Musatov  wrote:
> > >
> > > On Sunday, August 26, 2018 at 2:14:29 PM UTC-5, Oscar Benjamin wrote:
> > > > > > > > > >> On Fri, 24 Aug 2018 14:40:00 -0700, tomusatov wrote:
> > > > > > > > > >>
> > > > > > > > > >>> I am looking for a program able to output a set of 
> > > > > > > > > >>> integers meeting the
> > > > > > > > > >>> following requirement:
> > > > > > > > > >>>
> > > > > > > > > >>> a(n) is the minimum k > 0 such that n*2^k - 3 is prime, 
> > > > > > > > > >>> or 0 if no such
> > > > > > > > > >>> k exists
> > > > > > > > > >>>
> > > > > > > > > >>> Could anyone get me started? (I am an amateur)
> > > >
> > > > Fair enough. So finding a(n) when a(n)!=0 is straight-forward (simply
> > > > loop through testing k=1,2...) but the issue is determining for any
> > > > given n whether a(n)=0 i.e. that there does not exist k such that
> > > > n*2^k-3 is prime.
> > > >
> > > > Perhaps if you explain how you know that
> > > >a(72726958979572419805016319140106929109473069209) = 0
> > > > then that would suggest a way to code it.
> > > >
> > > Oscar, I simply asked someone and they provided me the number. I know 
> > > they often use Maple, but I was interested in Python.
> > > He also said some of the n are prime by Dirichlet's theorem. One is 
> > > 8236368172492875810638652252525796530412199592269.
> > 
> > If it is possible at all then it is certainly possible to do this in
> > Python but only for someone who knows the necessary maths. The purpose
> > of computers in these kinds of problems is that they are much faster
> > at number-crunching. You still need to know how (at least in
> > principle) you would do this by hand in order to program it in Python
> > or most likely anything else.
> > 
> > I don't think anyone here knows the answer to the mathematical
> > question "how do I prove that a(n)=0 for some n?". If you knew the
> > answer to that question then I'm sure many people could help you write
> > code for it.
> > 
> > Without that I think you need to go back to your mathematician friends
> > or do some more reading.
> > 
> > Are you sure that the problem you have posed here is solvable (i.e.
> > that whether or not a(n)=0 is decidable for any n)?
> > 
> > --
> > Oscar
> 
> My understanding is this: there are an infinite number of n's that are not 
> multiples of three, and yet will always be divisible by at least one of 22 
> primes for all values of k.
> 
> i.e. certain n values make the equation produce only composite numbers for 
> all values of k.

Just to be clear it is not the n I was referring to being composite but the 
result when certain n are fed into the n*2^k - 3
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Re: Writing a program to illustrate a fractal

On Sunday, August 26, 2018 at 3:13:00 PM UTC-5, Oscar Benjamin wrote:
> On Sun, 26 Aug 2018 at 20:52, Musatov  wrote:
> >
> > Thank you, Richard. If anyone is interested further, even in writing a 
> > Python code to generate the sequence or further preparing of an animation I 
> > would be delighted.
> 
> It would not take long to write code to plot your sequence if you
> first cover the basics of Python. What have you tried so far?
> 
> Have you read the python.org tutorial? Here's a page from there that
> mentions the Fibonacci sequence incidentally:
> https://docs.python.org/3/tutorial/modules.html
> 
> For plotting I suggest matplotlib:
> https://matplotlib.org/users/pyplot_tutorial.html
> 
> --
> Oscar

I have some learning to do, but if I get stuck I'll write back on this thread.
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Re: Generating a specific list of intsgers

On Sunday, August 26, 2018 at 3:07:41 PM UTC-5, Oscar Benjamin wrote:
> On Sun, 26 Aug 2018 at 20:32, Musatov  wrote:
> >
> > On Sunday, August 26, 2018 at 2:14:29 PM UTC-5, Oscar Benjamin wrote:
> > > > > > > > >> On Fri, 24 Aug 2018 14:40:00 -0700, tomusatov wrote:
> > > > > > > > >>
> > > > > > > > >>> I am looking for a program able to output a set of integers 
> > > > > > > > >>> meeting the
> > > > > > > > >>> following requirement:
> > > > > > > > >>>
> > > > > > > > >>> a(n) is the minimum k > 0 such that n*2^k - 3 is prime, or 
> > > > > > > > >>> 0 if no such
> > > > > > > > >>> k exists
> > > > > > > > >>>
> > > > > > > > >>> Could anyone get me started? (I am an amateur)
> > >
> > > Fair enough. So finding a(n) when a(n)!=0 is straight-forward (simply
> > > loop through testing k=1,2...) but the issue is determining for any
> > > given n whether a(n)=0 i.e. that there does not exist k such that
> > > n*2^k-3 is prime.
> > >
> > > Perhaps if you explain how you know that
> > >a(72726958979572419805016319140106929109473069209) = 0
> > > then that would suggest a way to code it.
> > >
> > Oscar, I simply asked someone and they provided me the number. I know they 
> > often use Maple, but I was interested in Python.
> > He also said some of the n are prime by Dirichlet's theorem. One is 
> > 8236368172492875810638652252525796530412199592269.
> 
> If it is possible at all then it is certainly possible to do this in
> Python but only for someone who knows the necessary maths. The purpose
> of computers in these kinds of problems is that they are much faster
> at number-crunching. You still need to know how (at least in
> principle) you would do this by hand in order to program it in Python
> or most likely anything else.
> 
> I don't think anyone here knows the answer to the mathematical
> question "how do I prove that a(n)=0 for some n?". If you knew the
> answer to that question then I'm sure many people could help you write
> code for it.
> 
> Without that I think you need to go back to your mathematician friends
> or do some more reading.
> 
> Are you sure that the problem you have posed here is solvable (i.e.
> that whether or not a(n)=0 is decidable for any n)?
> 
> --
> Oscar

My understanding is this: there are an infinite number of n's that are not 
multiples of three, and yet will always be divisible by at least one of 22 
primes for all values of k.

i.e. certain n values make the equation produce only composite numbers for all 
values of k.
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Re: Writing a program to illustrate a fractal

2018-08-26 Thread Oscar Benjamin

On Sun, 26 Aug 2018 at 20:52, Musatov  wrote:
>
> Thank you, Richard. If anyone is interested further, even in writing a Python 
> code to generate the sequence or further preparing of an animation I would be 
> delighted.

It would not take long to write code to plot your sequence if you
first cover the basics of Python. What have you tried so far?

Have you read the python.org tutorial? Here's a page from there that
mentions the Fibonacci sequence incidentally:
https://docs.python.org/3/tutorial/modules.html

For plotting I suggest matplotlib:
https://matplotlib.org/users/pyplot_tutorial.html

--
Oscar
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Re: Generating a specific list of intsgers

2018-08-26 Thread Oscar Benjamin

On Sun, 26 Aug 2018 at 20:32, Musatov  wrote:
>
> On Sunday, August 26, 2018 at 2:14:29 PM UTC-5, Oscar Benjamin wrote:
> > > > > > > >> On Fri, 24 Aug 2018 14:40:00 -0700, tomusatov wrote:
> > > > > > > >>
> > > > > > > >>> I am looking for a program able to output a set of integers 
> > > > > > > >>> meeting the
> > > > > > > >>> following requirement:
> > > > > > > >>>
> > > > > > > >>> a(n) is the minimum k > 0 such that n*2^k - 3 is prime, or 0 
> > > > > > > >>> if no such
> > > > > > > >>> k exists
> > > > > > > >>>
> > > > > > > >>> Could anyone get me started? (I am an amateur)
> >
> > Fair enough. So finding a(n) when a(n)!=0 is straight-forward (simply
> > loop through testing k=1,2...) but the issue is determining for any
> > given n whether a(n)=0 i.e. that there does not exist k such that
> > n*2^k-3 is prime.
> >
> > Perhaps if you explain how you know that
> >a(72726958979572419805016319140106929109473069209) = 0
> > then that would suggest a way to code it.
> >
> Oscar, I simply asked someone and they provided me the number. I know they 
> often use Maple, but I was interested in Python.
> He also said some of the n are prime by Dirichlet's theorem. One is 
> 8236368172492875810638652252525796530412199592269.

If it is possible at all then it is certainly possible to do this in
Python but only for someone who knows the necessary maths. The purpose
of computers in these kinds of problems is that they are much faster
at number-crunching. You still need to know how (at least in
principle) you would do this by hand in order to program it in Python
or most likely anything else.

I don't think anyone here knows the answer to the mathematical
question "how do I prove that a(n)=0 for some n?". If you knew the
answer to that question then I'm sure many people could help you write
code for it.

Without that I think you need to go back to your mathematician friends
or do some more reading.

Are you sure that the problem you have posed here is solvable (i.e.
that whether or not a(n)=0 is decidable for any n)?

--
Oscar
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[issue34510] Add add HTTPConnection.settimeout()

2018-08-26 Thread Collin Anderson



Change by Collin Anderson :


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nosy: collinanderson
priority: normal
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title: Add add HTTPConnection.settimeout()
type: enhancement

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Re: Writing a program to illustrate a fractal

On Sunday, August 26, 2018 at 2:35:13 PM UTC-5, Richard Damon wrote:
> On 8/26/18 1:58 PM, Musatov wrote:
> > On Sunday, August 26, 2018 at 12:49:16 PM UTC-5, Richard Damon wrote:
> >> On 8/26/18 12:48 PM, Dennis Lee Bieber wrote:
>  The sequence is defined by:
> 
>  For 1 <= n <= 3, a(n) = n; thereafter, a(2n) = a(n) + a(n+1), a(2n-1) = 
>  a(n) + a(n-2).
> 
> >>> I am not sure what 'fractal' property this sequence has that he
> >>> wants to 
> >> display.
> > I'm sorry, let me try to explain:
> >
> > Here is my output:
> > 1, 2, 3, 5, 4, 8, 7, 9, 7, 12, 13, 15, 11, 16, 17, 16, 14, 19, 21, 25, 20, 
> > 28, 27, 26, 24, 27, 31, 33, 28, 33, 32, 30, 31, 33, 35, 40, 35, 46, 44, 45, 
> > 41, 48, 53, 55, 47, 53, 54, 50, 51, 51, 53,
> >
> > It is an OEIS sequence. 
> >
> > I was told this image of the scatterplot emphasizes the 'fractal nature' of 
> > my sequence:
> >
> > https://oeis.org/A292575/a292575.png
> 
> Something is wrong with that image compared to the sequence, as the
> sequence is always positive, and in fact the lowest the sequence can get
> to is always increasing (as it starts always positive, and each term is
> the sum of two previous terms),while the graph is going negative.
> 
> (actually going to the definition of the sequence, the plot isn't of
> a(n) but a(n)-n, which can go negative)
> 
> I normally think for fractals as a sequence of patterns of increasing
> complexity, or a pattern looked at with increasing resolution revealing
> the growth pattern. This sequence isn't quite like that, but I suppose
> if you think of the sequence a(n) in the interval m <= n <= 2*m, and
> then the interval 2*m <= n <= 4*m, that second interval is somewhat like
> the first with some recursively added pattern (especially if you include
> the -n in the sequence).
> 
> That graph is probably the best way to show that pattern.
> 
> One thing that might help, is to clean up the definition of a(n) to be
> more directly computable, and  maybe even include the subtraction of n.
> 
> A rewriting of your rules would be:
> 
> a(n)
> 
> n=1,2,3:    a(n) = n
> 
> n>3, and even: a(n) = a(n/2) + a(n/2+1)
> 
> n>3 and odd: a(n) = a((n+1)/2) + a(n-3)/2)
> 
> If I have done my math right, this is the same sequence definition, but
> always defining what a(n) is equal to.
> 
> If we want to define the sequence b(n) = a(n) - n, we can transform the
> above by substitution
> 
> b(n)
> 
> n=1,2,3: b(n) = 0
> 
> n>3 and even: b(n) = a(n/2)+a(n/2+1)-n
> 
>     = b(n/2)+b(n/2+1) + n/2 + n/2+1 -n
> 
>     = b(n/2) + b(n/2+1) + 1
> 
> n>3 and odd: b(n) = a((n+1)/2) + a((n-3)/2) - n
> 
>     = b((n+1)/2) + b((n-3)/2) + (n+1)/2 + (n-3)/2 -n
> 
>     = b((n+1)/2) + b((n-3)/2) -1
> 
> -- 
> Richard Damon

Thank you, Richard. If anyone is interested further, even in writing a Python 
code to generate the sequence or further preparing of an animation I would be 
delighted.

Musatov
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Re: Writing a program to illustrate a fractal

On 8/26/18 1:58 PM, Musatov wrote:
> On Sunday, August 26, 2018 at 12:49:16 PM UTC-5, Richard Damon wrote:
>> On 8/26/18 12:48 PM, Dennis Lee Bieber wrote:
 The sequence is defined by:

 For 1 <= n <= 3, a(n) = n; thereafter, a(2n) = a(n) + a(n+1), a(2n-1) = 
 a(n) + a(n-2).

>>> I am not sure what 'fractal' property this sequence has that he
>>> wants to 
>> display.
> I'm sorry, let me try to explain:
>
> Here is my output:
> 1, 2, 3, 5, 4, 8, 7, 9, 7, 12, 13, 15, 11, 16, 17, 16, 14, 19, 21, 25, 20, 
> 28, 27, 26, 24, 27, 31, 33, 28, 33, 32, 30, 31, 33, 35, 40, 35, 46, 44, 45, 
> 41, 48, 53, 55, 47, 53, 54, 50, 51, 51, 53,
>
> It is an OEIS sequence. 
>
> I was told this image of the scatterplot emphasizes the 'fractal nature' of 
> my sequence:
>
> https://oeis.org/A292575/a292575.png

Something is wrong with that image compared to the sequence, as the
sequence is always positive, and in fact the lowest the sequence can get
to is always increasing (as it starts always positive, and each term is
the sum of two previous terms),while the graph is going negative.

(actually going to the definition of the sequence, the plot isn't of
a(n) but a(n)-n, which can go negative)

I normally think for fractals as a sequence of patterns of increasing
complexity, or a pattern looked at with increasing resolution revealing
the growth pattern. This sequence isn't quite like that, but I suppose
if you think of the sequence a(n) in the interval m <= n <= 2*m, and
then the interval 2*m <= n <= 4*m, that second interval is somewhat like
the first with some recursively added pattern (especially if you include
the -n in the sequence).

That graph is probably the best way to show that pattern.

One thing that might help, is to clean up the definition of a(n) to be
more directly computable, and  maybe even include the subtraction of n.

A rewriting of your rules would be:

a(n)

n=1,2,3:    a(n) = n

n>3, and even: a(n) = a(n/2) + a(n/2+1)

n>3 and odd: a(n) = a((n+1)/2) + a(n-3)/2)

If I have done my math right, this is the same sequence definition, but
always defining what a(n) is equal to.

If we want to define the sequence b(n) = a(n) - n, we can transform the
above by substitution

b(n)

n=1,2,3: b(n) = 0

n>3 and even: b(n) = a(n/2)+a(n/2+1)-n

    = b(n/2)+b(n/2+1) + n/2 + n/2+1 -n

    = b(n/2) + b(n/2+1) + 1

n>3 and odd: b(n) = a((n+1)/2) + a((n-3)/2) - n

    = b((n+1)/2) + b((n-3)/2) + (n+1)/2 + (n-3)/2 -n

    = b((n+1)/2) + b((n-3)/2) -1

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Re: Generating a specific list of intsgers

On Sunday, August 26, 2018 at 2:14:29 PM UTC-5, Oscar Benjamin wrote:
> On Sat, 25 Aug 2018 at 20:27, Musatov  wrote:
> >
> > On Saturday, August 25, 2018 at 2:18:09 PM UTC-5, Musatov wrote:
> > > On Saturday, August 25, 2018 at 1:52:17 PM UTC-5, Oscar Benjamin wrote:
> > > > > > >
> > > > > > >> On Fri, 24 Aug 2018 14:40:00 -0700, tomusatov wrote:
> > > > > > >>
> > > > > > >>> I am looking for a program able to output a set of integers 
> > > > > > >>> meeting the
> > > > > > >>> following requirement:
> > > > > > >>>
> > > > > > >>> a(n) is the minimum k > 0 such that n*2^k - 3 is prime, or 0 if 
> > > > > > >>> no such
> > > > > > >>> k exists
> > > > > > >>>
> > > > > > >>> Could anyone get me started? (I am an amateur)
> > > > > > >>
> > > > > > >> That's more a maths question than a programming question. Find 
> > > > > > >> out how to
> > > > > > >> tackle it mathematically, and then we can code it.
> > > >
> > > > Looks like it's zero for any multiple of 3 (apart from 3 itself). This
> > > > makes sense since if n is a equal to b*3 for some integer b then
> > > > n*2^k - 3 = b*3*2^k - 3 = (b*2^k - 1)*3
> > > > which can only be prime if
> > > > b*2^k - 1 = 1
> > > > which can only be true if b=1 (since k>0) implying that n=3. So for
> > > > any *other* multiple of 3 you must necessarily have a(n) = 0.
> > > >
> > > > The above means that you can handle all multiples of 3 but how do you
> > > > know that you won't hit an infinite loop when n is not a multiple of
> > > > 3?
> >
> > Rather, I should say one such n is 
> > 72726958979572419805016319140106929109473069209 (which is not divisible by 
> > 3)
> 
> Fair enough. So finding a(n) when a(n)!=0 is straight-forward (simply
> loop through testing k=1,2...) but the issue is determining for any
> given n whether a(n)=0 i.e. that there does not exist k such that
> n*2^k-3 is prime.
> 
> Perhaps if you explain how you know that
>a(72726958979572419805016319140106929109473069209) = 0
> then that would suggest a way to code it.
> 
> --
> Oscar
Oscar, I simply asked someone and they provided me the number. I know they 
often use Maple, but I was interested in Python.

He also said some of the n are prime by Dirichlet's theorem. One is 
8236368172492875810638652252525796530412199592269.
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Re: Generating a specific list of intsgers

2018-08-26 Thread Oscar Benjamin

On Sat, 25 Aug 2018 at 20:27, Musatov  wrote:
>
> On Saturday, August 25, 2018 at 2:18:09 PM UTC-5, Musatov wrote:
> > On Saturday, August 25, 2018 at 1:52:17 PM UTC-5, Oscar Benjamin wrote:
> > > > > >
> > > > > >> On Fri, 24 Aug 2018 14:40:00 -0700, tomusatov wrote:
> > > > > >>
> > > > > >>> I am looking for a program able to output a set of integers 
> > > > > >>> meeting the
> > > > > >>> following requirement:
> > > > > >>>
> > > > > >>> a(n) is the minimum k > 0 such that n*2^k - 3 is prime, or 0 if 
> > > > > >>> no such
> > > > > >>> k exists
> > > > > >>>
> > > > > >>> Could anyone get me started? (I am an amateur)
> > > > > >>
> > > > > >> That's more a maths question than a programming question. Find out 
> > > > > >> how to
> > > > > >> tackle it mathematically, and then we can code it.
> > >
> > > Looks like it's zero for any multiple of 3 (apart from 3 itself). This
> > > makes sense since if n is a equal to b*3 for some integer b then
> > > n*2^k - 3 = b*3*2^k - 3 = (b*2^k - 1)*3
> > > which can only be prime if
> > > b*2^k - 1 = 1
> > > which can only be true if b=1 (since k>0) implying that n=3. So for
> > > any *other* multiple of 3 you must necessarily have a(n) = 0.
> > >
> > > The above means that you can handle all multiples of 3 but how do you
> > > know that you won't hit an infinite loop when n is not a multiple of
> > > 3?
>
> Rather, I should say one such n is 
> 72726958979572419805016319140106929109473069209 (which is not divisible by 3)

Fair enough. So finding a(n) when a(n)!=0 is straight-forward (simply
loop through testing k=1,2...) but the issue is determining for any
given n whether a(n)=0 i.e. that there does not exist k such that
n*2^k-3 is prime.

Perhaps if you explain how you know that
   a(72726958979572419805016319140106929109473069209) = 0
then that would suggest a way to code it.

--
Oscar
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[issue34497] Remove needless set operator restriction

2018-08-26 Thread Raymond Hettinger



Raymond Hettinger  added the comment:

Sorry Dan, we're going to pass on this one.  The current behavior was an 
intentional design choice by Guido and reflects a careful balance between some 
difficult trade-offs.

An early and permanent mistake in Python's design is that list.__iadd__() and 
list.extend() both accept any input iterable.  For extend(), this proved to be 
useful.  In contrast, __iadd__() was a recurring bug magnet.  People would 
routinely type "s=['abc']; s+='def'" expecting to get ['abc', 'def'] rather 
than ['abc', 'd', 'e', 'f'].   Based on this experience, Guido wisely opined 
that math operators on other concrete collection classes should be restricted 
working with members of their own class.

When abstract base classes were introduced, a seemingly inconsistent decision 
was made.  The Set ABCs allowed the math operators to accept any input iterable 
and did not provide the spelled-out method names (union, intersection, 
difference, etc).

IIRC, there were several reasons for this.  It kept the total number of methods 
to a manageable size (important so as to not unduly burden implementers of 
concrete classes).  Also, having a same type restriction is at odds with some 
of the design goals and use cases for collections ABCs.  Additionally, the code 
for the mixin methods is simpler without the restrictions.

When dict views were implemented, they followed the Set ABCs.  This gave them 
fewer methods than sets but also gave them fewer restrictions.  For the most 
part, these design trade-offs have worked out well in practice.  The existing 
behavior is neither "needless" nor "arbitrary".  It was the result of careful 
consideration by GvR on what works best for most people, most of the time.

--
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stage: patch review -> resolved
status: open -> closed

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Re: Writing a program to illustrate a fractal

On Sunday, August 26, 2018 at 12:49:16 PM UTC-5, Richard Damon wrote:
> On 8/26/18 12:48 PM, Dennis Lee Bieber wrote:
> >> The sequence is defined by:
> >>
> >> For 1 <= n <= 3, a(n) = n; thereafter, a(2n) = a(n) + a(n+1), a(2n-1) = 
> >> a(n) + a(n-2).
> >>
> > Confusing explanation -- do you really mean that for n>=4 you are
> > returning TWO values? 

For a(4)..a(19) we have that: 2+3=5, 1+3=4, 3+5=8, 2+5=7, 5+4=9, 3+4=7, 4+8=12, 
5+8=13, 8+7=15, 4+7=11, 7+9=16, 8+9=17, 9+7=16, 7+7=14, 7+12=19, 9+12=21.

If so, it is not a strict function. I'd also write it
> > as
> 
> I think they intend that a(n) is defined for n being an integer (or
> maybe just the Natural Numbers, since it isn't defined for values below 1)
> 
> The two provided definitions provide the recursive definition for even
> and odd values.
> 
> I am not sure what 'fractal' property this sequence has that he wants to
> display.

I'm sorry, let me try to explain:

Here is my output:
1, 2, 3, 5, 4, 8, 7, 9, 7, 12, 13, 15, 11, 16, 17, 16, 14, 19, 21, 25, 20, 28, 
27, 26, 24, 27, 31, 33, 28, 33, 32, 30, 31, 33, 35, 40, 35, 46, 44, 45, 41, 48, 
53, 55, 47, 53, 54, 50, 51, 51, 53,

It is an OEIS sequence. 

I was told this image of the scatterplot emphasizes the 'fractal nature' of my 
sequence:

https://oeis.org/A292575/a292575.png
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[issue34509] Starting to use gcc-8 on CI

2018-08-26 Thread Jun Aruga



Jun Aruga  added the comment:

> it would be better to set up a buildbot running GCC 8, or switching one of 
> our existing workers to it.  We want to keep the pre-merge CI as stable as 
> possible, and using a bleeding-edge compiler doesn't strike me as 
> particularly stable.

Oh it seems that we have already had the CI environment as buildbot. I did not 
know that. Yeah it might be better to add it as a buildbot.

https://buildbot.python.org/all/#/

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Re: Writing a program to illustrate a fractal

On 8/26/18 12:48 PM, Dennis Lee Bieber wrote:
>> The sequence is defined by:
>>
>> For 1 <= n <= 3, a(n) = n; thereafter, a(2n) = a(n) + a(n+1), a(2n-1) = a(n) 
>> + a(n-2).
>>
>   Confusing explanation -- do you really mean that for n>=4 you are
> returning TWO values? If so, it is not a strict function. I'd also write it
> as

I think they intend that a(n) is defined for n being an integer (or
maybe just the Natural Numbers, since it isn't defined for values below 1)

The two provided definitions provide the recursive definition for even
and odd values.

I am not sure what 'fractal' property this sequence has that he wants to
display.
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[issue34509] Starting to use gcc-8 on CI

2018-08-26 Thread Zachary Ware



Zachary Ware  added the comment:

I think rather than switching Travis CI (or VSTS) to GCC 8, it would be better 
to set up a buildbot running GCC 8, or switching one of our existing workers to 
it.  We want to keep the pre-merge CI as stable as possible, and using a 
bleeding-edge compiler doesn't strike me as particularly stable.

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[issue11193] test_subprocess test_undecodable_env error on AIX

2018-08-26 Thread Gregory P. Smith



Gregory P. Smith  added the comment:

https://github.com/python/cpython/pull/8939 and 
https://github.com/python/cpython/pull/8946

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[issue11193] test_subprocess test_undecodable_env error on AIX

2018-08-26 Thread Gregory P. Smith



Change by Gregory P. Smith :


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[issue11193] test_subprocess test_undecodable_env error on AIX

2018-08-26 Thread Gregory P. Smith



Gregory P. Smith  added the comment:

someone with modern AIX access reopen if this specific issue still appears to 
exist after the 3.8 and 3.7 PRs finish merging.

--
nosy: +gregory.p.smith
stage: patch review -> resolved
status: open -> closed
title: test_subprocess error on AIX -> test_subprocess test_undecodable_env 
error on AIX
versions: +Python 3.7

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[issue34497] Remove needless set operator restriction

2018-08-26 Thread Raymond Hettinger



Change by Raymond Hettinger :


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[issue34494] simple "sequence" class ignoring len

2018-08-26 Thread Raymond Hettinger



Raymond Hettinger  added the comment:

I concur with Josh.  This matches the documented behavior and isn't a bug. 
Marking as closed.

There are potentially two ways to stop sequence iteration, either by using len 
or by waiting for IndexError.  Python uses the latter to allow lists to be 
dynamically resized during iteration and because checking len on every 
iteration would be expensive.  

If someone doesn't read the docs, and assumes Python uses len, and writes an 
inconsistent class (one where len doesn't match the point where IndexError is 
raised), then there is little we can do to prevent that person from being 
"surprised".

--
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stage:  -> resolved
status: open -> closed

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[issue34503] Reference leak in PyErr_SetObject()

2018-08-26 Thread Xiang Zhang



Change by Xiang Zhang :


--
resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue34509] Starting to use gcc-8 on CI

2018-08-26 Thread Jun Aruga



Change by Jun Aruga :


--
keywords: +patch
pull_requests: +8418
stage:  -> patch review

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[issue34171] Lib/trace.cover not removed by the clean target

2018-08-26 Thread Zachary Ware



Zachary Ware  added the comment:

> Can we manually ssh into the buildbots from the buildbot master and delete 
> the file?

No, there is no access to the workers except for the connection created by each 
worker for the purpose of buildbot communication (and individually by each 
worker owner).

> It may be easier to remove "trace.cover" before testing every time than clean 
> up all buildbots once.

I agree.  Alternately, the test could be changed to avoid that assertion; it's 
strange that the test could fail just because a file could happen to exist 
outside of the test's control.

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[issue34509] Starting to use gcc-8 on CI

2018-08-26 Thread Jun Aruga

New submission from Jun Aruga :

This ticket is from below conversation on python-dev mailing list.
https://mail.python.org/pipermail/python-dev/2018-August/155011.html

Right now the Python project Travis CI is running on gcc-4.8.4 for coverage
testing.
I want to replace it or add the latest version gcc-8 case.

The benefit to use gcc-8 is,

* It is important to run on the old version 4.8 but, it is also meaningful to
follow the latest version and care issues such as warnings on the latest
version gcc.
* I am working in Fedora project that is using gcc version 8 as a main c
compiler. If the Python project care gcc-8, that might be helpful for people
who maintain Python Debian/Fedora package or Installer on Mac/Windows.

The demerit is

* Right now the gcc-4.8 is used for the coverage. The total running time on
gcc-8 might be longer than current one.
* To run the latest gcc-8, we can add the repository [1] with the way [2][3],
but I am not sure whether the repository is stable.

I would show you 2 cases to use gcc-8 on Linux.

[1] https://launchpad.net/~ubuntu-toolchain-r/+archive/ubuntu/test
[2]
https://docs.travis-ci.com/user/installing-dependencies/#installing-packages-from-a-custom-apt-repository
[3] https://docs.travis-ci.com/user/languages/c/#gcc-on-os-x
[4] Ruby
https://travis-ci.org/junaruga/ruby/builds/418242410
https://github.com/junaruga/ruby/blob/feature/ci-new-gcc/.travis.yml
https://github.com/ruby/ruby/pull/1937
[5] Trinity
Example for gcc-8 on both Linux and Mac.
https://travis-ci.org/trinityrnaseq/trinityrnaseq
https://github.com/trinityrnaseq/trinityrnaseq/blob/master/.travis.yml

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nosy: junaruga
priority: normal
severity: normal
status: open
title: Starting to use gcc-8 on CI
type: enhancement
versions: Python 3.8

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[issue34503] Reference leak in PyErr_SetObject()



miss-islington  added the comment:


New changeset 204fb459ca1d77c2eab02a3191ba2d2216ff2d72 by Miss Islington (bot) 
in branch '3.6':
bpo-34503: Fix refleak in PyErr_SetObject() (GH-8934)
https://github.com/python/cpython/commit/204fb459ca1d77c2eab02a3191ba2d2216ff2d72


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[issue34503] Reference leak in PyErr_SetObject()



miss-islington  added the comment:


New changeset 2caf86ff6d72d625f86db78c6e90fdaf09e8f703 by Miss Islington (bot) 
in branch '3.7':
bpo-34503: Fix refleak in PyErr_SetObject() (GH-8934)
https://github.com/python/cpython/commit/2caf86ff6d72d625f86db78c6e90fdaf09e8f703


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[issue34503] Reference leak in PyErr_SetObject()

2018-08-26 Thread Xiang Zhang



Xiang Zhang  added the comment:


New changeset a2eefa67542c25617a58c03a27c17fd48e2a0856 by Xiang Zhang (Alexey 
Izbyshev) in branch 'master':
bpo-34503: Fix refleak in PyErr_SetObject() (GH-8934)
https://github.com/python/cpython/commit/a2eefa67542c25617a58c03a27c17fd48e2a0856


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[issue34503] Reference leak in PyErr_SetObject()



Change by miss-islington :


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[issue34503] Reference leak in PyErr_SetObject()



Change by miss-islington :


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[issue34508] return of non-parenthesized star-unpacking expression a SyntaxError

2018-08-26 Thread Mark Dickinson



Change by Mark Dickinson :


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Writing a program to illustrate a fractal