Re: [Tutor] Pythonic way

[Alan Gauld via Tutor]

On 20/11/2018 22:35, Steven D'Aprano wrote:
> On Tue, Nov 20, 2018 at 08:22:01PM +, Alan Gauld via Tutor wrote:
> 
>> I think that's a very deliberate feature of Python going back
>> to its original purpose of being a teaching language that
>> can be used beyond the classroom.
> 
> I don't think that is correct -- everything I've read is that Guido 
> designed Python as a scripting language for use in the "Amoeba" 
> operating system.

I think both are true. Guido was working on Amoeba at the time
he built Python so it was an obvious choice of platform, although
he first built it on a Mac. But he didn't set out specifically to
build a scripting language for Amoeba but rather to build "a descendant
of ABC" which was also usable in the real world, specifically The C/Unix
world.

To do that he believed it had to address the major barriers to ABC
which were 1)being capable of being extended and 2) improved I/O.

My source for that conclusion is Guido's forward to
"Programming Python" 1st edition.

https://www.python.org/doc/essays/foreword/

Also his comments when he set up the "Computer Programming for
Everybody" initiative, which he led for several years. (Which
I can't locate...)

So I believe that ease of teaching was definitely part
of the original game plan and was definitely a factor in
some of the later developments around v2.0 or so.

-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos


___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way

[Steven D'Aprano]

On Tue, Nov 20, 2018 at 08:22:01PM +, Alan Gauld via Tutor wrote:

> I think that's a very deliberate feature of Python going back
> to its original purpose of being a teaching language that
> can be used beyond the classroom.

I don't think that is correct -- everything I've read is that Guido 
designed Python as a scripting language for use in the "Amoeba" 
operating system.

You might be thinking of Python's major influence, ABC, which was 
designed as a teaching language -- but not by Guido himself. Guido was 
heavily influenced by ABC, both in what to do, and what not to do.

https://www.artima.com/intv/pythonP.html

http://python-history.blogspot.com/2009/02/early-language-design-and-development.html



-- 
Steve
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way

[Mark Lawrence]

On 20/11/2018 18:08, Avi Gross wrote:



We have two completely separate ways to format strings that end up with fairly 
similar functionality. Actually, there is an implicit third way 



You could argue five ways :-)

1. C printf style formatting 
https://docs.python.org/3/library/stdtypes.html#printf-style-string-formatting
2. New style string formatting 
https://docs.python.org/3/library/string.html#string-formatting
3. f-strings 
https://docs.python.org/3/reference/lexical_analysis.html#f-strings
4. String templates 
https://docs.python.org/3/library/string.html#template-strings
5. String methods 
https://docs.python.org/3/library/stdtypes.html#string-methods


Any advance on five anybody?

--
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence

___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way

[Alan Gauld via Tutor]

On 20/11/2018 18:08, Avi Gross wrote:
> ... So there isn’t really ONE pythonic way for many things. 

That's true and, I think, inevitable for anything developed
in the open source world. If you compare it to a language
entirely controlled by a single mind - like Oberon or Eiffel
say - then there is much less consistency. But how many people
actually use Oberon or Eiffel in the real world these days?

> We have two completely separate ways to format strings

And many options for concurrency and for running external
programs. Much of it is history and the need for backward
compatibility.

And let's not even think about web and GUI frameworks!

> ..you can do much without creating objects or using functional programming
> ...If you come from an OO background, you can have fun making endless classes
>...If you lie functional programming with factories that churn out functions
> ...There are other such paradigms supported including lots of miniature 
> sub-languages

> ...effectively means being open to multiple ways 

I think that's a very deliberate feature of Python going back
to its original purpose of being a teaching language that
can be used beyond the classroom. It was always intended
to support multi paradigms. After all, every programmer
should be aware of multiple paradigms and when to best
use each.

BUt, Python is currently suffering the same fate as C++ in
that, as it becomes more mainstream in real-world industry,
the feature demands upon it inevitably move it away from some
of those original teaching based ideas. It is certainly
a much harder language to learn today than it was when
I started in 1998. From a pure academic CS view many changes
are good (eg. iterators and meta programming) but from a
non-academic beginner(or even high school student) they are
just plain confusing. It's all part of being a success in
the real world. The funding for development comes from the
industrial user community not the high schools or colleges,
so their needs come first.

PS. Just back from vacation so still catching up on the
last week's discussions!

-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos


___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

[Tutor] Pythonic way

[Avi Gross]

This is not a question or reply. Nor is it short. If not interested, feel free 
to delete.

 

It is an observation based on recent experiences.

 

We have had quite a few messages that pointed out how some people approach  
solving a problem using subconscious paradigms inherited from their past. This 
includes people who never programmed and are thinking of how they might do it 
manually as well as people who are proficient in one or more other computer 
languages and their first attempt to visualize the solution may lead along 
paths that are possibly doable in Python but not optimal or even suggested.

 

I recently had to throw together a routine that would extract info from 
multiple SAS data files and join them together on one key into a large 
DataFrame (or data.frame or other such names for a tabular object.). Then I 
needed to write them out to disk either as a CSV or XLSX file for future use.

 

Since I have studied and used (not to mention abused) many programming 
languages, my first thought was to do this in R. It has lots of the tools 
needed to do such things including packages (sort of like modules you can 
import but not exactly) and I have done many data/graphics programs in it. I 
then redid it in Python after some thought.

 

The pseudocode outline is:

 

*   Read in all the files into a set of data.frame objects.
*   Trim back the variables/columns of some of them as many are not needed.
*   Join them together on a common index using a full or outer join.
*   Save the result on disk as a Comma Separated Values file.
*   Save the result on disk as a named tab in a new style EXCEL file.

 

I determined some of what I might us such as the needed built-in commands, 
packages and functions I could use for the early parts but ran into an 
annoyance as some of the files contained duplicate entries. Luckily, the R 
function reduce (not the same as map/reduce) is like many things in R and takes 
a list of items and makes it work. Also, by default, it renames duplicates so 
if you have ALPHA in multiple places, it names them ALPHA.x and ALPHA.x.x and 
other variations.

 

df_joined <- reduce(df_list, full_join, by = "COMMON")

 

Mind you, when I stripped away many of the columns not needed in some of the 
files, there were fewer duplicates and a much smaller output file.

 

But I ran into a wall later. Saving into a CSV is trivial. There are multiple 
packages meant to be used for saving into a XLSX file but they all failed for 
me. One wanted something in JAVA and another may want PERL and some may want 
packages I do not have installed. So, rather than bash my head against the 
wall, Itwisted and used the best XSLX maker there is. I opened the CSV file in 
EXCEL manually and did a SAVE AS …

 

Then I went to plan C (no, not the language C or its many extensions like C++) 
as I am still learning Python and have not used it much. As an exercise, I 
decided to learn how to do this in Python using tools/modules like numpy and 
pandas that I have not had much need for as well as additional tools for 
reading and writing files in other formats.

 

My first attempts gradually worked, after lots of mistakes and looking at 
manual pages. It followed an eclectic set of paradigms but worked.  Not 
immediately, as I ran into a problem in that the pandas version of a join did 
not tolerate duplicate column names when used on a list. I could get it to 
rename the left or right list (adding a suffix a suffix) when used on exactly 
two DataFrames. So, I needed to take the first df and do a df.join(second, …) 
then take that and join the third and so on. I also needed to keep telling it 
to set the index to the common value for each and every df including the newly 
joined series. And, due to size, I chose to keep deleting df no longer in use 
but that would not be garbage collected.

 

I then looked again at how to tighten it up in a more pythonic way. In English 
(my sixth language since we are talking about languages  ) I did some things 
linearly then shifted it to a list method. I used lists of file names and lists 
of the df made from each file after removing unwanted columns. (NOTE: I use 
“column” but depending on language and context I mean variable or field or axis 
or many other ways to say a group of related information in a tabular structure 
that crosses rows or instances.)

 

So I was able to do my multi-step join more like this:

 

join_with_list = dflist[1:]

current = df1

suffix = 1

 

for df in join_with_list:

current = current.join(df, how='outer', rsuffix='_'+str(suffix))

suffix += 1

current.set_index('ID')

 

In this formulation, the intermediate DataFrame objects held in current will 
silently be garbage collected as nothing points to them, for example. Did I 
mention these were huge files?

 

The old code was much longer and error prone as I had a df1, df2, … df8 as well 
as other intermediates and was easy to copy and paste then 

Re: [Tutor] pythonic

[Albert-Jan Roskam]

Op 2 apr. 2018 15:31 schreef Steven D'Aprano :
>
> On Mon, Apr 02, 2018 at 06:49:52AM -0600, Mats Wichmann wrote:
> > On 04/02/2018 02:56 AM, Alan Gauld via Tutor wrote:
> > > On 02/04/18 04:19, Steven D'Aprano wrote:
> > >> On Sun, Apr 01, 2018 at 10:58:51PM +0100, Alan Gauld via Tutor wrote:
> > >>> On01/04/18 20:20, Albert-Jan Roskam wrote:
> >  fmt="%Y-%m-%d %H:%M\n"
> >  f.write(now.strftime(fmt))
> >  Lately I've been using format(), which uses __format__, because I find 
> >  it slightly more readable:
> >  format(datetime.now(), "%Y-%m-%d %H:%M")
> > >>> Interesting,
> > >>> I didn't know that format() recognised the datetime format codes.
> > >> It doesn't. It is the datetime object that recognises them. format()
> > >> merely passes the format string to the datetime.__format__ method, which
> > >> is what recognises the codes. It doesn't care what it is.
> > > Aha! That makes sense. I've never really used format() so have never
> > > bothered to find out how it works. To the point that until this thread I
> > > hadn't realized we even had a __format__() operator.
> > >
> > > As I said, I need to do some reading. Obviously a gap in my python
> > > education.
> > >
> >
> > so since we're all learning things here, how would this play out with
> > the new f-strings?
>
> I don't think f-strings are even a bit Pythonic.

"There should be one-- and preferably only one --obvious way to do it.":
1-str.format
2-% interpolation
3-string.Template
4-f strings
-...

I think that at least a few of these methods should become deprecated. Maybe 2 
and 3? (though I use 2 all the time!). Not sure about 4. A proper templating 
language like Jinja might be more desirable to have in the standard library, 
addition to a simple string substitution mechanism
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[Steven D'Aprano]

On Mon, Apr 02, 2018 at 04:28:10PM +0200, Peter Otten wrote:

> > They look like string constants, but they're actually a hidden call to
> > eval().
> 
> But because you cannot f-ify a string variable (without an additional eval() 
> call) you aren't tempted to feed them user-provided data.

If only that were the case...

https://mail.python.org/pipermail/python-list/2018-March/731967.html

He reads f-strings from user-supplied data, then evals them.

But its okay, he's only doing it within his own organisation, and we all 
know that "insiders" are always 100% trusted. "Insider attack" is just a 
pair of words. Right?


> As I'm getting tired of writing
> 
> "...{foo}...{bar}...".format(foo=foo, bar=bar, ...)

You can write:

template.format(**(locals()))

or possibly nicer still:

template.format_map(locals())


-- 
Steve
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[Mats Wichmann]

On 04/02/2018 08:28 AM, Peter Otten wrote:
> Steven D'Aprano wrote:
> 
>> On Mon, Apr 02, 2018 at 06:49:52AM -0600, Mats Wichmann wrote:
> 
>>> so since we're all learning things here, how would this play out with
>>> the new f-strings?
>>
>> I don't think f-strings are even a bit Pythonic.
>>
>> They look like string constants, but they're actually a hidden call to
>> eval().
> 
> But because you cannot f-ify a string variable (without an additional eval() 
> call) you aren't tempted to feed them user-provided data.
> 
>> They can only be used once, and are not re-usable (unlike proper
>> templates):
> 
> You can't eat your cake an have it. As "proper templates" they would indeed 
> be as dangerous as eval().
> 
>> By my count, they violate at least three of the Zen of Python:
>>
>> Explicit is better than implicit.
>> Simple is better than complex.
>> Special cases aren't special enough to break the rules.
> 
> As I'm getting tired of writing
> 
> "...{foo}...{bar}...".format(foo=foo, bar=bar, ...)
> 
> lately I'd say they win big in the "practicality beats you-name-it" area.

so swooping back to the origial code, it seems there are several options
for expressing the output. Picking one of the lines (and replacing the
writes to a file with prints for simplicity):

print("Date: {}-{}-{} {}:{}\n".format(now.year,
now.month,
now.day,
now.hour,
now.minute))
print("Date:", format(now, "%Y-%m-%d %H:%M"))
print(f"Date: {now:%Y-%m-%d %H:%M}")

those aren't exactly identical, since the using %m-%d form causes
zero-padding:

Date: 2018-4-2 10:23

Date: 2018-04-02 10:23
Date: 2018-04-02 10:23


For me, I don't know if the f-string version is the most Pythonic, but
it has an appealing conciseness in this particular context :)



___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[Peter Otten]

Steven D'Aprano wrote:

> On Mon, Apr 02, 2018 at 06:49:52AM -0600, Mats Wichmann wrote:

>> so since we're all learning things here, how would this play out with
>> the new f-strings?
> 
> I don't think f-strings are even a bit Pythonic.
> 
> They look like string constants, but they're actually a hidden call to
> eval().

But because you cannot f-ify a string variable (without an additional eval() 
call) you aren't tempted to feed them user-provided data.

> They can only be used once, and are not re-usable (unlike proper
> templates):

You can't eat your cake an have it. As "proper templates" they would indeed 
be as dangerous as eval().

> By my count, they violate at least three of the Zen of Python:
> 
> Explicit is better than implicit.
> Simple is better than complex.
> Special cases aren't special enough to break the rules.

As I'm getting tired of writing

"...{foo}...{bar}...".format(foo=foo, bar=bar, ...)

lately I'd say they win big in the "practicality beats you-name-it" area.


___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[Steven D'Aprano]

On Mon, Apr 02, 2018 at 06:49:52AM -0600, Mats Wichmann wrote:
> On 04/02/2018 02:56 AM, Alan Gauld via Tutor wrote:
> > On 02/04/18 04:19, Steven D'Aprano wrote:
> >> On Sun, Apr 01, 2018 at 10:58:51PM +0100, Alan Gauld via Tutor wrote:
> >>> On01/04/18 20:20, Albert-Jan Roskam wrote:
>  fmt="%Y-%m-%d %H:%M\n"
>  f.write(now.strftime(fmt))
>  Lately I've been using format(), which uses __format__, because I find 
>  it slightly more readable:
>  format(datetime.now(), "%Y-%m-%d %H:%M")
> >>> Interesting,
> >>> I didn't know that format() recognised the datetime format codes.
> >> It doesn't. It is the datetime object that recognises them. format() 
> >> merely passes the format string to the datetime.__format__ method, which 
> >> is what recognises the codes. It doesn't care what it is.
> > Aha! That makes sense. I've never really used format() so have never
> > bothered to find out how it works. To the point that until this thread I
> > hadn't realized we even had a __format__() operator.
> > 
> > As I said, I need to do some reading. Obviously a gap in my python
> > education.
> > 
> 
> so since we're all learning things here, how would this play out with
> the new f-strings?

I don't think f-strings are even a bit Pythonic.

They look like string constants, but they're actually a hidden call to 
eval().

py> x = 2
py> f'hello {3*x}'
'hello 6'

So they can execute arbitrary code that has arbitrary side-effects:

py> L = []
py> f'hello {L.append(1) or 99}'
'hello 99'
py> L
[1]


By my count, they violate at least three of the Zen of Python:

Explicit is better than implicit.
Simple is better than complex.
Special cases aren't special enough to break the rules.

They can only be used once, and are not re-usable (unlike proper 
templates):


py> x = 2
py> template = f'x = {x}'  # gets the value of x now
py> print(template)
x = 2
py> x = 99
py> print(template)  # still has the old value of x
x = 2


However, they do use the same mechanism as format():

py> from datetime import datetime
py> t = datetime.now()
py> format(t, '%H:%M')
'23:22'
py> f'{t:%H:%M}'
'23:22'



-- 
Steve
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[leam hall]

On Mon, Apr 2, 2018 at 9:01 AM, David Rock  wrote:

> It’s just as (if not more) pythonic to use the standard libraries. It’s very 
> common in a professional environment to not have access to outside (i.e., 
> internet) resources.  I wouldn’t venture into Pypi unless there’s something 
> you can’t do well with what’s already provided by default.

+1.

Use standard libraries; most places I've worked didn't allow a lot of
non-standard library code at all. If something is in the standard
library you have some level of assurance that the maintenance is
moderated and monitored.
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[David Rock]

> On Mar 30, 2018, at 04:15, George Fischhof  wrote:
> 
> 2.)
> argparse
> 
> it is good, but you can write more Pythonic code using click
> https://pypi.python.org/pypi/click/
> it is also Pythonic to use / know the Python ecosystem (the packages)

It’s just as (if not more) pythonic to use the standard libraries. It’s very 
common in a professional environment to not have access to outside (i.e., 
internet) resources.  I wouldn’t venture into Pypi unless there’s something you 
can’t do well with what’s already provided by default.


— 
David Rock
da...@graniteweb.com




___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[Mats Wichmann]

On 04/02/2018 02:56 AM, Alan Gauld via Tutor wrote:
> On 02/04/18 04:19, Steven D'Aprano wrote:
>> On Sun, Apr 01, 2018 at 10:58:51PM +0100, Alan Gauld via Tutor wrote:
>>> On01/04/18 20:20, Albert-Jan Roskam wrote:
 fmt="%Y-%m-%d %H:%M\n"
 f.write(now.strftime(fmt))
 Lately I've been using format(), which uses __format__, because I find it 
 slightly more readable:
 format(datetime.now(), "%Y-%m-%d %H:%M")
>>> Interesting,
>>> I didn't know that format() recognised the datetime format codes.
>> It doesn't. It is the datetime object that recognises them. format() 
>> merely passes the format string to the datetime.__format__ method, which 
>> is what recognises the codes. It doesn't care what it is.
> Aha! That makes sense. I've never really used format() so have never
> bothered to find out how it works. To the point that until this thread I
> hadn't realized we even had a __format__() operator.
> 
> As I said, I need to do some reading. Obviously a gap in my python
> education.
> 

so since we're all learning things here, how would this play out with
the new f-strings?
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[Alan Gauld via Tutor]

On 02/04/18 04:19, Steven D'Aprano wrote:
> On Sun, Apr 01, 2018 at 10:58:51PM +0100, Alan Gauld via Tutor wrote:
>> On01/04/18 20:20, Albert-Jan Roskam wrote:
>>> fmt="%Y-%m-%d %H:%M\n"
>>> f.write(now.strftime(fmt))
>>> Lately I've been using format(), which uses __format__, because I find it 
>>> slightly more readable:
>>> format(datetime.now(), "%Y-%m-%d %H:%M")
>> Interesting,
>> I didn't know that format() recognised the datetime format codes.
> It doesn't. It is the datetime object that recognises them. format() 
> merely passes the format string to the datetime.__format__ method, which 
> is what recognises the codes. It doesn't care what it is.
Aha! That makes sense. I've never really used format() so have never
bothered to find out how it works. To the point that until this thread I
hadn't realized we even had a __format__() operator.

As I said, I need to do some reading. Obviously a gap in my python
education.

-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos

___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[Steven D'Aprano]

On Sun, Apr 01, 2018 at 10:58:51PM +0100, Alan Gauld via Tutor wrote:
> On01/04/18 20:20, Albert-Jan Roskam wrote:
> > fmt="%Y-%m-%d %H:%M\n"
> > f.write(now.strftime(fmt))
> > Lately I've been using format(), which uses __format__, because I find it 
> > slightly more readable:
> > format(datetime.now(), "%Y-%m-%d %H:%M")
> Interesting,
> I didn't know that format() recognised the datetime format codes.

It doesn't. It is the datetime object that recognises them. format() 
merely passes the format string to the datetime.__format__ method, which 
is what recognises the codes. It doesn't care what it is.


py> class Spam:
... def __format__(self, template):
... return template.replace("^DD^", " surprise ")
...
py> format(Spam(), "some^DD^string")
'some surprise string'


-- 
Steve
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[Alan Gauld via Tutor]

On01/04/18 20:20, Albert-Jan Roskam wrote:
> fmt="%Y-%m-%d %H:%M\n"
> f.write(now.strftime(fmt))
> Lately I've been using format(), which uses __format__, because I find it 
> slightly more readable:
> format(datetime.now(), "%Y-%m-%d %H:%M")
Interesting,
I didn't know that format() recognised the datetime format codes.
I assumed it would just use the printf codes.

Time to do some more reading I see.

-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos

___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[Albert-Jan Roskam]

On Mar 30, 2018 10:39, Alan Gauld via Tutor  wrote:
>
> On 30/03/18 03:48, Pat Martin wrote:
>
> > the "right" way to do it in python?
>
> More or less, a couple of comments below...
>
> > def Main():
>
> Python function names begin with a lowercase letter by convention.
>
> > """Run if run as a program."""
> > parser = argparse.ArgumentParser()
> ...
>
> >
> > now = datetime.datetime.now()
> > slug = args.title.replace(" ", "-").lower()
> >
> > with open("{}.md".format(slug), 'w') as f:
> > f.write("Title: {}\n".format(args.title))
> > f.write("Date: {}-{}-{} {}:{}\n".format(now.year,
> > now.month,
> > now.day,
> > now.hour,
> > now.minute))
>
> Formatting of dates and times is usually done using
> the time.strftime function which is specifically
> designed for that. It might be worth taking a peek
> at the docs on that one. You can call it directly
> on a datetime object - 'now' in your case:
>
> fmt="%Y-%m-%d %H:%M\n"
> f.write(now.strftime(fmt))

Lately I've been using format(), which uses __format__, because I find it 
slightly more readable:
format(datetime.now(), "%Y-%m-%d %H:%M")
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[Pat Martin]

Thank you all for the ideas and comments, it is appreciated.

I have some refactoring to do now.

On Fri, Mar 30, 2018 at 2:22 AM, Peter Otten <__pete...@web.de> wrote:

> Pat Martin wrote:
>
> > I have written the following program. It generates a template for Pelican
> > web site static generator. It works just fine, it generates the template
> > and then I put the info in it to customize. But I was wondering, is this
> > the "right" way to do it in python?
>
> You may rewrite the code creating the output as a loop:
>
> now_str = now.replace(microsecond=0).isoformat(" ")
> with open("{}.md".format(slug), 'w') as f:
> for name, value in [
> ("Title", args.title),
> ("Date", now_str),
> ("Modified", now_str),
> ("Category", args.category),
> ("Slug", slug),
> ("Authors", args.author),
> ("Summary", ""),
> ]:
> print(name, value, sep=": ", file=f)
>
>
> If you want to format more than one date the same way you should put the
> code into a function, no matter whether you pick your, my, or Alan's much
> more common way to implement it
>
> def format_time(dt):
>return ...
>
> ...
> ("Date", format_time(now)),
> ("Modified", format_time(modified)),
> ...
>
> The idea behind my suggestions is the DRY (don't repeat yourself) principle
> which applies to code written in any language.
>
> > #!/usr/bin/env python3
> > """Generate a Pelican markdown base page."""
> >
> > import argparse
> > import datetime
> >
> >
> > def Main():
> > """Run if run as a program."""
> > parser = argparse.ArgumentParser()
> > parser.add_argument("-T", "--title", type=str, required=True,
> > help='Title for site, also generates the slug',
> > metavar="")
> > parser.add_argument("-c", "--category", required=True,
> > help='Category or categories of post',
> metavar="")
> > parser.add_argument("-t", "--tags", type=str, required=True,
> > help="Tags for post", metavar="")
> > parser.add_argument("-a", "--author", type=str, default="Pat Martin",
> > help="Author of post", metavar="")
> > args = parser.parse_args()
> >
> > now = datetime.datetime.now()
> > slug = args.title.replace(" ", "-").lower()
> >
> > with open("{}.md".format(slug), 'w') as f:
> > f.write("Title: {}\n".format(args.title))
> > f.write("Date: {}-{}-{} {}:{}\n".format(now.year,
> > now.month,
> > now.day,
> > now.hour,
> > now.minute))
> > f.write("Modified: {}-{}-{} {}:{}\n".format(now.year,
> > now.month,
> > now.day,
> > now.hour,
> > now.minute))
> > f.write("Category: {}\n".format(args.category))
> > f.write("Slug: {}\n".format(slug))
> > f.write("Authors: {}\n".format(args.author))
> > f.write("Summary: \n")
> >
> >
> > if __name__ == "__main__":
> > Main()
>
>
> ___
> Tutor maillist  -  Tutor@python.org
> To unsubscribe or change subscription options:
> https://mail.python.org/mailman/listinfo/tutor
>
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[George Fischhof]

2018-03-30 4:48 GMT+02:00 Pat Martin :

> Hello all,
>
> I have written the following program. It generates a template for Pelican
> web site static generator. It works just fine, it generates the template
> and then I put the info in it to customize. But I was wondering, is this
> the "right" way to do it in python?
>
> #!/usr/bin/env python3
> """Generate a Pelican markdown base page."""
>
> import argparse
> import datetime
>
>
> def Main():
> """Run if run as a program."""
> parser = argparse.ArgumentParser()
> parser.add_argument("-T", "--title", type=str, required=True,
> help='Title for site, also generates the slug',
> metavar="")
> parser.add_argument("-c", "--category", required=True,
> help='Category or categories of post', metavar="")
> parser.add_argument("-t", "--tags", type=str, required=True,
> help="Tags for post", metavar="")
> parser.add_argument("-a", "--author", type=str, default="Pat Martin",
> help="Author of post", metavar="")
> args = parser.parse_args()
>
> now = datetime.datetime.now()
> slug = args.title.replace(" ", "-").lower()
>
> with open("{}.md".format(slug), 'w') as f:
> f.write("Title: {}\n".format(args.title))
> f.write("Date: {}-{}-{} {}:{}\n".format(now.year,
> now.month,
> now.day,
> now.hour,
> now.minute))
> f.write("Modified: {}-{}-{} {}:{}\n".format(now.year,
> now.month,
> now.day,
> now.hour,
> now.minute))
> f.write("Category: {}\n".format(args.category))
> f.write("Slug: {}\n".format(slug))
> f.write("Authors: {}\n".format(args.author))
> f.write("Summary: \n")
>
>
> if __name__ == "__main__":
> Main()
>
>
>
> Thanks for any input.
>
> WP
> ___
> Tutor maillist  -  Tutor@python.org
> To unsubscribe or change subscription options:
> https://mail.python.org/mailman/listinfo/tutor
>



Hi Pat,

my thoughts:


1.)
def Main():

function names are written with small letter with underscore between the
words
check PEP-8
https://www.python.org/dev/peps/pep-0008/
http://docs.python-guide.org/en/latest/writing/style/

It is better to name the functions according to what they do, in this case
for example: create_template() or something like that


2.)
argparse

it is good, but you can write more Pythonic code using click
https://pypi.python.org/pypi/click/
it is also Pythonic to use / know the Python ecosystem (the packages)


3.)
with open("{}.md".format(slug), 'w') as f:
   f.write("Date: {}-{}-{} {}:{}\n".format(now.year,
now.month,

Python is mainly about readability
https://www.python.org/dev/peps/pep-0020/

you can use more meaningful variable names: template_file instead of f
if you have Python 3.6, you can use the newest formatting method, which is
more readable:
template_file.write(f"Date: {now.moth}-{now.day}") etc

https://www.python.org/dev/peps/pep-0498/

the more readable open:
slug_file_name = f"{slug}.md"
with open(slug_file_name, "w") as slug_file:

and if you use Python 3, the open should contain encoding:
with open(slug_file_name, "w", encoding="UTF-8") as slug_file:


BR,
George
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[Peter Otten]

Pat Martin wrote:

> I have written the following program. It generates a template for Pelican
> web site static generator. It works just fine, it generates the template
> and then I put the info in it to customize. But I was wondering, is this
> the "right" way to do it in python?

You may rewrite the code creating the output as a loop:

now_str = now.replace(microsecond=0).isoformat(" ")
with open("{}.md".format(slug), 'w') as f:
for name, value in [
("Title", args.title),
("Date", now_str),
("Modified", now_str),
("Category", args.category),
("Slug", slug),
("Authors", args.author),
("Summary", ""),
]:
print(name, value, sep=": ", file=f)


If you want to format more than one date the same way you should put the 
code into a function, no matter whether you pick your, my, or Alan's much 
more common way to implement it

def format_time(dt):
   return ...

...
("Date", format_time(now)),
("Modified", format_time(modified)),
...

The idea behind my suggestions is the DRY (don't repeat yourself) principle 
which applies to code written in any language.

> #!/usr/bin/env python3
> """Generate a Pelican markdown base page."""
> 
> import argparse
> import datetime
> 
> 
> def Main():
> """Run if run as a program."""
> parser = argparse.ArgumentParser()
> parser.add_argument("-T", "--title", type=str, required=True,
> help='Title for site, also generates the slug',
> metavar="")
> parser.add_argument("-c", "--category", required=True,
> help='Category or categories of post', metavar="")
> parser.add_argument("-t", "--tags", type=str, required=True,
> help="Tags for post", metavar="")
> parser.add_argument("-a", "--author", type=str, default="Pat Martin",
> help="Author of post", metavar="")
> args = parser.parse_args()
> 
> now = datetime.datetime.now()
> slug = args.title.replace(" ", "-").lower()
> 
> with open("{}.md".format(slug), 'w') as f:
> f.write("Title: {}\n".format(args.title))
> f.write("Date: {}-{}-{} {}:{}\n".format(now.year,
> now.month,
> now.day,
> now.hour,
> now.minute))
> f.write("Modified: {}-{}-{} {}:{}\n".format(now.year,
> now.month,
> now.day,
> now.hour,
> now.minute))
> f.write("Category: {}\n".format(args.category))
> f.write("Slug: {}\n".format(slug))
> f.write("Authors: {}\n".format(args.author))
> f.write("Summary: \n")
> 
> 
> if __name__ == "__main__":
> Main()


___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic

[Alan Gauld via Tutor]

On 30/03/18 03:48, Pat Martin wrote:

> the "right" way to do it in python?

More or less, a couple of comments below...

> def Main():

Python function names begin with a lowercase letter by convention.

> """Run if run as a program."""
> parser = argparse.ArgumentParser()
...

> 
> now = datetime.datetime.now()
> slug = args.title.replace(" ", "-").lower()
> 
> with open("{}.md".format(slug), 'w') as f:
> f.write("Title: {}\n".format(args.title))
> f.write("Date: {}-{}-{} {}:{}\n".format(now.year,
> now.month,
> now.day,
> now.hour,
> now.minute))

Formatting of dates and times is usually done using
the time.strftime function which is specifically
designed for that. It might be worth taking a peek
at the docs on that one. You can call it directly
on a datetime object - 'now' in your case:

fmt="%Y-%m-%d %H:%M\n"
f.write(now.strftime(fmt))


-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos


___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

[Tutor] pythonic

[Pat Martin]

Hello all,

I have written the following program. It generates a template for Pelican
web site static generator. It works just fine, it generates the template
and then I put the info in it to customize. But I was wondering, is this
the "right" way to do it in python?

#!/usr/bin/env python3
"""Generate a Pelican markdown base page."""

import argparse
import datetime


def Main():
"""Run if run as a program."""
parser = argparse.ArgumentParser()
parser.add_argument("-T", "--title", type=str, required=True,
help='Title for site, also generates the slug',
metavar="")
parser.add_argument("-c", "--category", required=True,
help='Category or categories of post', metavar="")
parser.add_argument("-t", "--tags", type=str, required=True,
help="Tags for post", metavar="")
parser.add_argument("-a", "--author", type=str, default="Pat Martin",
help="Author of post", metavar="")
args = parser.parse_args()

now = datetime.datetime.now()
slug = args.title.replace(" ", "-").lower()

with open("{}.md".format(slug), 'w') as f:
f.write("Title: {}\n".format(args.title))
f.write("Date: {}-{}-{} {}:{}\n".format(now.year,
now.month,
now.day,
now.hour,
now.minute))
f.write("Modified: {}-{}-{} {}:{}\n".format(now.year,
now.month,
now.day,
now.hour,
now.minute))
f.write("Category: {}\n".format(args.category))
f.write("Slug: {}\n".format(slug))
f.write("Authors: {}\n".format(args.author))
f.write("Summary: \n")


if __name__ == "__main__":
Main()



Thanks for any input.

WP
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic ascii decoding!

[eryk sun]

On Mon, Jul 31, 2017 at 3:39 PM, bruce  wrote:
>
> So, is there a quick/dirty approach I can use to simply strip out the
> "non-ascii" chars. I know, this might not be the "best/pythonic" way,
> and that it might result in loss of some data/chars, but I can live
> with it for now.

Ignore or replace the non-ASCII characters. For example:

>>> print 's\xffp\xffa\xffm'.decode('ascii', 'ignore')
spam
>>> print 's\xffp\xffa\xffm'.decode('ascii', 'replace')
s�p�a�m
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] pythonic ascii decoding!

[Mats Wichmann]

On 07/31/2017 09:39 AM, bruce wrote:
> Hi guys.
> 
> Testing getting data from a number of different US based/targeted
> websites. So the input data source for the most part, will be "ascii".
> I'm getting a few "weird" chars every now and then asn as fas as I can
> tell, they should be utf-8.
> 
> However, the following hasn;t always worked:
> s=str(s).decode('utf-8').strip()
> 
> So, is there a quick/dirty approach I can use to simply strip out the
> "non-ascii" chars. I know, this might not be the "best/pythonic" way,
> and that it might result in loss of some data/chars, but I can live
> with it for now.
> 
> thoughts/comments ??

It's easy enough to toss chars if you don't care what's being tossed,
which sounds like your case, something like:

''.join(i for i in s if ord(i) < 128)


but there's actually lots to think about here (I'm sure others will jump in)

- Python2 strings default to ascii, Python3 to unicode, there may be
some excitement with the use of ord() depending on how the string is
passed around
- websites will tell you their encoding, which you could and probably
should make use of
- web scraping with Python is a pretty well developed field, perhaps you
might want to use one of the existing projects? (https://scrapy.org/ is
pretty famous, certainly not the only one)
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

[Tutor] pythonic ascii decoding!

[bruce]

Hi guys.

Testing getting data from a number of different US based/targeted
websites. So the input data source for the most part, will be "ascii".
I'm getting a few "weird" chars every now and then asn as fas as I can
tell, they should be utf-8.

However, the following hasn;t always worked:
s=str(s).decode('utf-8').strip()

So, is there a quick/dirty approach I can use to simply strip out the
"non-ascii" chars. I know, this might not be the "best/pythonic" way,
and that it might result in loss of some data/chars, but I can live
with it for now.

thoughts/comments ??

thanks
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic review (descriptors)

[Alan Gauld]

On 28/04/15 10:55, Sage Hack wrote:

I'm looking for somebody willing to review parts of this code
https://github.com/SageHack/cloud-buster and let me know what is not
Pythonic :P


 https://github.com/SageHack/cloud-buster/tree/master/bust/descriptor

The thing that jumps out to me is your use of class variables to hold a 
dictionary of instance responses based on the instance ID. That

pattern looks like this, and you use it in every class:

class SomeClass:
classvar = {}

def __init__(self,id):
   self.id = id
def __get__(self...):
   v = getSomeValue()
   sel.classvar[self.id] = v

Normally you'd store instance specific data in the instance
itself not in a class variable. also you overwrite the
classvariable entry for each instance every time you call
the get(). Is that really what you want?

The other thing is that you should have docstrings for
both the classes and methods.

Finally, and not Python specific, You have several classes
sharing the same 'ID' data - self.domain - that's usually
a bad OOP smell. Only one class should be mastering any
given type of  data, so maybe your other classes are
really methods of whichever is the master class? Particularly
since they don't have any explicit methods (also a bad OOP
smell) of their own.


--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos


___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

[Tutor] Pythonic review (descriptors)

[Sage Hack]

I'm looking for somebody willing to review parts of this code
https://github.com/SageHack/cloud-buster and let me know what is not
Pythonic :P

I want to improve my Python coding skills but I'm not sure exactly what
to study next.

Right now I'm trying to use descriptors correctly and I'd like to know
if this is about right
https://github.com/SageHack/cloud-buster/tree/master/bust/descriptor

Thanks :)
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic review (descriptors)

[Alan Gauld]

On 28/04/15 10:55, Sage Hack wrote:

I'm looking for somebody willing to review parts of this code
https://github.com/SageHack/cloud-buster and let me know what is not
Pythonic :P



https://github.com/SageHack/cloud-buster/tree/master/bust/descriptor


Another point re the PageTitle class:

class PageTitle(object):

titles = {}

def __init__(self, url, host=None):
self.url = url
self.host = host

def __get__(self, obj=None, objtype=None):...

@property
def id(self):
if self.host:
return self.url+':'+self.host
else:
return self.url


There is not much point in calculating the id each time,
it could simply be set in the init(). You never change
the url or host.


--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos


___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor

[Tutor] Pythonic way of concatenation of elements in an array

[spawgi]

Hello,

My code is -

l = len(m)
item = str(m[1])
for i in range(2,l):
item = item + - + str(m[i])

This code is part of a bigger function. It works fine. But I am not happy
with the way I have written it. I think there is a better (Pythonic) way to
rewrite it.
If anyone knows how to improve this snippet, I would be very thankful.

Thanks and Regards,
Sumod


-- 
http://spawgi.wordpress.com
We can do it and do it better.
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way of concatenation of elements in an array

[Steven D'Aprano]

spa...@gmail.com wrote:

Hello,

My code is -

l = len(m)
item = str(m[1])
for i in range(2,l):
item = item + - + str(m[i])

This code is part of a bigger function. It works fine. But I am not happy
with the way I have written it. I think there is a better (Pythonic) way to
rewrite it.
If anyone knows how to improve this snippet, I would be very thankful.


(1) Never use l as a variable name, as it looks too much like 1.


(2) Use meaningful names. When posting snippets for help, you should show 
example data.



(3) You almost never need to iterate over an index by hand. Instead iterate 
over the items themselves. That is, instead of this:


for i in len(sequence):
do_something_with( sequence[i] )

do this instead:

for item in sequence:
do_something_with( item )


and similar variations.


(4) When you want only part of a sequence, use slicing to extract just the 
parts you care about.



(5) When assembling strings from substrings, never use repeated concatenation 
using + as that can be EXTREMELY slow. Use str.join to build the string in one 
assignment, instead of multiple assignments.


Your code shown above is *very* inefficient and will be PAINFULLY slow if m is 
very large. To understand why, you should read this article:


http://www.joelonsoftware.com/articles/fog000319.html

In this case, you can replace your snippet with this:

result = '-'.join(str(item) for item in m[1:])



For example:

py m = [1, 2, hello world, (23, 42), 5]
py '-'.join(str(item) for item in m[1:])
'2-hello world-(23, 42)-5'



--
Steven

___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way of concatenation of elements in an array

[spawgi]

Hello Steven,

Thanks a lot for the detailed answer. I will implement your suggestions.
Really appreciate it.

Thanks and Regards,
Sumod

On Fri, Jan 27, 2012 at 4:34 AM, Steven D'Aprano st...@pearwood.infowrote:

 spa...@gmail.com wrote:

 Hello,

 My code is -

 l = len(m)
 item = str(m[1])
 for i in range(2,l):
item = item + - + str(m[i])

 This code is part of a bigger function. It works fine. But I am not happy
 with the way I have written it. I think there is a better (Pythonic) way
 to
 rewrite it.
 If anyone knows how to improve this snippet, I would be very thankful.


 (1) Never use l as a variable name, as it looks too much like 1.


 (2) Use meaningful names. When posting snippets for help, you should show
 example data.


 (3) You almost never need to iterate over an index by hand. Instead
 iterate over the items themselves. That is, instead of this:

 for i in len(sequence):
do_something_with( sequence[i] )

 do this instead:

 for item in sequence:
do_something_with( item )


 and similar variations.


 (4) When you want only part of a sequence, use slicing to extract just the
 parts you care about.


 (5) When assembling strings from substrings, never use repeated
 concatenation using + as that can be EXTREMELY slow. Use str.join to build
 the string in one assignment, instead of multiple assignments.

 Your code shown above is *very* inefficient and will be PAINFULLY slow if
 m is very large. To understand why, you should read this article:

 http://www.joelonsoftware.com/**articles/fog000319.htmlhttp://www.joelonsoftware.com/articles/fog000319.html

 In this case, you can replace your snippet with this:

 result = '-'.join(str(item) for item in m[1:])



 For example:

 py m = [1, 2, hello world, (23, 42), 5]
 py '-'.join(str(item) for item in m[1:])
 '2-hello world-(23, 42)-5'



 --
 Steven

 __**_
 Tutor maillist  -  Tutor@python.org
 To unsubscribe or change subscription options:
 http://mail.python.org/**mailman/listinfo/tutorhttp://mail.python.org/mailman/listinfo/tutor




-- 
http://spawgi.wordpress.com
We can do it and do it better.
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way of concatenation of elements in an array

[Andre' Walker-Loud]

Hi Steven,

 (5) When assembling strings from substrings, never use repeated concatenation 
 using + as that can be EXTREMELY slow. Use str.join to build the string in 
 one assignment, instead of multiple assignments.
 
 Your code shown above is *very* inefficient and will be PAINFULLY slow if m 
 is very large. To understand why, you should read this article:
 
 http://www.joelonsoftware.com/articles/fog000319.html
 
 In this case, you can replace your snippet with this:
 
 result = '-'.join(str(item) for item in m[1:])

This was an interesting article.  I have only had one programming class, and 
that was 15 years ago or so, so these are not issues I am aware of.

I often find myself joining strings (and have mostly used + to do it).  An 
alternate method I use is, for eg.

print('here is a string %s which has many variables %s %s %s I have to sort 
out' %(s1,s2,s3,s4))

where the various strings (s1 - s4) have been determined elsewhere, perhaps in 
a loop.

Is this method any better at combining strings than the +?  My first guess 
would be no, but that is really just a guess.


Thanks,

Andre
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic nested lists

[Alan Gauld]

col speed ajarnco...@gmail.com wrote


HI again, I realise that I should have included more information in 
the

above e-mail. Here goes:

a/ I have a 9*9 nested list called rows, which contains the given 
numbers

in a sudoku puzzle - with 0s where the blanks go.

b/ I create roworder (roworder = [[str(j)+str(i) for i in range(9)] 
for j in
range(9)]) - [[00 -- 08], [10 -- 18] -- [80 -- 
88]]


c/ I populate a dictionary (dic) with keys from roworder and 
values from

rows

d/ I loop through the dict, changing any value0 to be set(range(1, 
10))- a

list of possible numbers.

e/ Then I do:
for i in roworder:
   notPoss = set([dic[j] for j in i if type(dic[j]) == int])
   for k in j:
   if type(dic[k]) == set:
   dic[k].difference_update(notPoss)

thus removing the numbers that exist in the row from the possible 
numbers


I need to do this for the columns and squares aswell, which is why I 
do:


That approach should work.
Personally I'd probably create a Square class and bae my data on 9 
squares.
Each square can return a row(of 3 items) given an index and a 
column(of 3 items)

given an index.

class Square:
 def __init__(self, size=3): self.cells = [0 for n in 
range(size*size)] ...

 def __str__(self):...
 def getRow(self,n): ...
 def getCol(self,n):...
 def setCell(self,x,y,value)
 def check(self):...

Thus I'd build my rows and columns dynamically from the squares rather
than the other way round. It just feels more natural to me.
But your approach should work too.

However I confess I haven't studied you code in detail.
Is there any specific problem or question you have or are you looking
for general feedback?

HTH,


--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/



___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

[Tutor] Pythonic nested lists

[col speed]

Message: 6
Date: Tue, 28 Sep 2010 13:15:26 +0700
From: col speed ajarnco...@gmail.com
To: tutor@python.org
Subject: [Tutor] Pythonic nested lists
Message-ID:
   aanlktimdykbkzxaacbaagpq_faz50ruy=bcr81dqx...@mail.gmail.com
Content-Type: text/plain; charset=iso-8859-1

Hi all,
I've been trying to write a programme that solves sudoku problems for a
while now. I'm getting close, but would like to ask a few questions about
the most pythonic way of doing some things.
I've decided to create nested lists (row order, column order and square
order) which correspond with dictionary keys - the values of which are the
numbers given in the puzzle - so I can loop through the dict in different
orders.
I think the first two are OK, but the square order list seems extremely
messy and I would love some pointers. What I have is as follows:

roworder = [[str(j)+str(i) for i in range(9)] for j in range(9)]
colorder = zip(*roworder)
#here comes the problem!
start, index = 0,0
sqorder = []
for i in range(9):
   sqorder.append([])
   for j in range(start, start+3):
   sqorder[i].extend(roworder[j][index:index+3])
   if index == 6:
   index = 0
   else:
   index += 3
   if i == 2 or i == 5:
   start += 3

Any comments at all would be gratefully received.
Thanks in advance
Colin

___

HI again, I realise that I should have included more information in the
above e-mail. Here goes:

a/ I have a 9*9 nested list called rows, which contains the given numbers
in a sudoku puzzle - with 0s where the blanks go.

b/ I create roworder (roworder = [[str(j)+str(i) for i in range(9)] for j in
range(9)]) - [[00 -- 08], [10 -- 18] -- [80 -- 88]]

c/ I populate a dictionary (dic) with keys from roworder and values from
rows

d/ I loop through the dict, changing any value0 to be set(range(1, 10))- a
list of possible numbers.

e/ Then I do:
for i in roworder:
notPoss = set([dic[j] for j in i if type(dic[j]) == int])
for k in j:
if type(dic[k]) == set:
dic[k].difference_update(notPoss)

thus removing the numbers that exist in the row from the possible numbers

I need to do this for the columns and squares aswell, which is why I do:

colorder = zip(*roworder) - (create a nested list column wise rather than
row wise)
and want to create a square order list - which is what the above mess
does.

I hope this clarifies things.
Thanks again
Colin
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

[Tutor] Pythonic nested lists

[col speed]

Hi all,
I've been trying to write a programme that solves sudoku problems for a
while now. I'm getting close, but would like to ask a few questions about
the most pythonic way of doing some things.
I've decided to create nested lists (row order, column order and square
order) which correspond with dictionary keys - the values of which are the
numbers given in the puzzle - so I can loop through the dict in different
orders.
I think the first two are OK, but the square order list seems extremely
messy and I would love some pointers. What I have is as follows:

roworder = [[str(j)+str(i) for i in range(9)] for j in range(9)]
colorder = zip(*roworder)
#here comes the problem!
start, index = 0,0
sqorder = []
for i in range(9):
sqorder.append([])
for j in range(start, start+3):
sqorder[i].extend(roworder[j][index:index+3])
if index == 6:
index = 0
else:
index += 3
if i == 2 or i == 5:
start += 3

Any comments at all would be gratefully received.
Thanks in advance
Colin
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way to normalize vertical whitespace

[spir]

Le Fri, 08 May 2009 13:03:47 -0400,
pyt...@bdurham.com s'exprima ainsi:

[...]
 Approaches:
 1. split text to list of lines that get stripped then:
 a. walk this list building a new list of lines that track and
 ignore extra blank lines
 -OR-
 b. re-join lines and replace '\n\n\n' wth' \n\n' until no more
 '\n\n\n' matches exist
 2. use regular expressions to match and replace whitespace
 pattern of 3 or more adjacent \n's with surrounding whitespace
 3. a 3rd party text processing library designed for efficiently
 cleaning up text
 Thanks!

You should try 1a and 1b if only to have written the code at least once ;-) The 
set of python string methods is very complete and practicle.
Still, in this case, 2 is rather straightforward and simple. If you cannot 
figure out the proper pattern, have a look at 
http://www.amk.ca/python/howto/regex/ and/or ask again the list. 

Denis
--
la vita e estrany
___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

[Tutor] Pythonic way to normalize vertical whitespace

[python]

Note: Following cross-posted to python-list where it got queued
due to suspicious subject line.
I'm looking for suggestions on technique (not necessarily code)
about the most pythonic way to normalize vertical whitespace in
blocks of text so that there is never more than 1 blank line
between paragraphs. Our source text has newlines normalized to
single newlines (\n vs. combinations of \r and \n), but there may
be leading and trailing whitespace around each newline.
Approaches:
1. split text to list of lines that get stripped then:
a. walk this list building a new list of lines that track and
ignore extra blank lines
-OR-
b. re-join lines and replace '\n\n\n' wth' \n\n' until no more
'\n\n\n' matches exist
2. use regular expressions to match and replace whitespace
pattern of 3 or more adjacent \n's with surrounding whitespace
3. a 3rd party text processing library designed for efficiently
cleaning up text
Thanks!
___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way to normalize vertical whitespace

[bob gailer]

pyt...@bdurham.com wrote:
Note: Following cross-posted to python-list where it got queued due to 
suspicious subject line.


I'm looking for suggestions on technique (not necessarily code) about 
the most pythonic way to normalize vertical whitespace in blocks of 
text so that there is never more than 1 blank line between paragraphs. 
Our source text has newlines normalized to single newlines (\n vs. 
combinations of \r and \n), but there may be leading and trailing 
whitespace around each newline.


I can't follow that! Please provide a before and after example.



Approaches:

1. split text to list of lines that get stripped then:

a. walk this list building a new list of lines that track and ignore 
extra blank lines


-OR-

b. re-join lines and replace '\n\n\n' wth' \n\n' until no more 
'\n\n\n' matches exist


2. use regular expressions to match and replace whitespace pattern of 
3 or more adjacent \n's with surrounding whitespace


3. a 3rd party text processing library designed for efficiently 
cleaning up text


Thanks!



___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor
  



--
Bob Gailer
Chapel Hill NC
919-636-4239
___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way to normalize vertical whitespace

[Kent Johnson]

On Fri, May 8, 2009 at 1:03 PM,  pyt...@bdurham.com wrote:
 Note: Following cross-posted to python-list where it got queued due to
 suspicious subject line.

 I'm looking for suggestions on technique (not necessarily code) about the
 most pythonic way to normalize vertical whitespace in blocks of text so that
 there is never more than 1 blank line between paragraphs. Our source text
 has newlines normalized to single newlines (\n vs. combinations of \r and
 \n), but there may be leading and trailing whitespace around each newline.

 Approaches:

 1. split text to list of lines that get stripped then:

 a. walk this list building a new list of lines that track and ignore extra
 blank lines

 -OR-

 b. re-join lines and replace '\n\n\n' wth' \n\n' until no more '\n\n\n'
 matches exist

 2. use regular expressions to match and replace whitespace pattern of 3 or
 more adjacent \n's with surrounding whitespace

 3. a 3rd party text processing library designed for efficiently cleaning up
 text

1 sounds simple enough. That is the first thing I thought of. 2 should
also be easy if you have any regex-fu and might turn out to be faster
if you have a lot of text.

Kent
___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

[Tutor] Pythonic way to extract delimited substrings

[Malcolm Greene]

Suggestions on the best way to extract delimited substrings strings from
a larger string?

Background: I have a long multi-line string with expressions delimited
with '(' and ')' markers. I would like to extract these substrings and
process them in a loop.

Because the left and right delimiters are different from each other
*and* multi-char strings, it would appear that the .split() method would
not be an appropriate tool for this work.

I know how to do this task with regular expressions, but I'm always
cautious about using a bazooka when a hammer will suffice.

What strategy would you recommend?

1. Write a simple parsing function using string primitives (find,
slicing)

2. Use regular expressions

3. Use a 3rd party string processing module

Thanks!
Malcolm

___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way to extract delimited substrings

[Kent Johnson]

Malcolm Greene wrote:
 Suggestions on the best way to extract delimited substrings strings from
 a larger string?
 
 Background: I have a long multi-line string with expressions delimited
 with '(' and ')' markers. I would like to extract these substrings and
 process them in a loop.

 What strategy would you recommend?

If you just want to get the text between ( and ), re.findall() or 
re.finditer() is probably the simplest way to do it. If it is more 
complicated than that (e.g. nesting, escape chars) then I would probably 
look at pyparsing.

Kent
___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way to extract delimited substrings

[Alan Gauld]

Malcolm Greene [EMAIL PROTECTED] wrote in

 Background: I have a long multi-line string with expressions 
 delimited
 with '(' and ')' markers. I would like to extract these substrings 
 and
 process them in a loop.

 I know how to do this task with regular expressions, but I'm always
 cautious about using a bazooka when a hammer will suffice.

Sounds like an ideal candidate for regex and findall to me.

If you have to stop a tank a bazooka may be the right tool...

Alan G. 


___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

[Tutor] Pythonic way to try a few times, then raise exception?

[Allen Fowler]

Hello,

I have a block of code buried deep in a module  that I expect to fail 
periodically. (Calls to other machines over slow network, and such.)

Generally, though,  trying it a second / third will work.

Is there clean way to write this on Python?

Thanks

 __
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com ___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way to try a few times, then raise exception?

[Alan Gauld]

Allen Fowler [EMAIL PROTECTED] wrote

 I have a block of code buried deep in a module  
 that I expect to fail periodically. 
 (Calls to other machines over slow network, and such.)
 
 Generally, though,  trying it a second / third will work.
 
 Is there clean way to write this on Python?

There was a thread on this a few days ago but I can't find it now...

In general if you only have a few (eg hundreds) things to 
check you can run a loop inside a loop and exit it with break
if it works. Pdeudo code:

for item in list:
for attempt in range(3):
 result = accessItem(item)
 if result == OK: break
 else: sleep(T)   # optional pause to regroup if needed...
else: logError(item)

But I'm not sure if that's what you count as clean!

If the volumes being processed it is usually better to 
gather the failures up for seondary processing after 
getting through the successful ones. This is a much 
more efficient way of handling high data volumes.

HTH

-- 
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld

___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic way to try a few times, then raise exception?

[johnf]

On Friday 26 October 2007 03:17:47 pm Alan Gauld wrote:
 Allen Fowler [EMAIL PROTECTED] wrote

  I have a block of code buried deep in a module
  that I expect to fail periodically.
  (Calls to other machines over slow network, and such.)
 
  Generally, though,  trying it a second / third will work.
 
  Is there clean way to write this on Python?

 There was a thread on this a few days ago but I can't find it now...

 In general if you only have a few (eg hundreds) things to
 check you can run a loop inside a loop and exit it with break
 if it works. Pdeudo code:

 for item in list:
 for attempt in range(3):
  result = accessItem(item)
  if result == OK: break
  else: sleep(T)   # optional pause to regroup if needed...
 else: logError(item)

 But I'm not sure if that's what you count as clean!

 If the volumes being processed it is usually better to
 gather the failures up for seondary processing after
 getting through the successful ones. This is a much
 more efficient way of handling high data volumes.

 HTH

What about placing the try in a function and call the function from a loop 
passing the variable to check (computer name).  Then each failure will not 
cause the app to stop processing.  Use a counter in the calling procedure to 
the number of attempts.

-- 
John Fabiani
___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

[Tutor] Pythonic? Building a full path from a visual file tree

[stv]

Hey all,

I would like to expand the visual representation of a tree
hierarchy, given below, where child-ness is defined by indentation,
and folder-ness is highlighted with a trailing '/'

Input (test.txt):
dir1/
file1
file2
1-1/
file3
file4
dir2/
file5

The desired output is a fully qualified path for each input line:
dir1/
dir1/file1
dir1/file2
dir1/1-1/
dir1/1-1/file3
dir1/1-1/file4
dir2/
dir2/file5

I considered several brute-force solutions, but I persevered and came
to, what I think, is a more Pythonic solution. What do you think?

import string

def expand_tree(filetree):
  indent = '\t'
  stack = []
  for f in filetree:
indents = f.count(indent)
while len(stack)  indents: stack.pop()
stack.append(f.strip())
yield string.join(stack,'')
if not f.endswith('/'): stack.pop()

lines = [line.rstrip() for line in file('test.txt')]
for i in expand_tree(lines): print i

Those familiar with subversion (particularly, svnlook tree
/path/to/repos) may recognize the problem space and the sample input
(except that I simplified things a bit here, using a tab to indicate
level-of-hierarchy instead of a single space, which could appear in
the filename).  The real-world solution will use a regex to find run
of spaces at the start of element 'f'. It will also get input from
stdin instead of a file.

Questions:

Is the list comprehension the right idiom for getting a file into a
list, without the EOL chars? I'm hard-pressed to see how it could be
more concise, but this is Python :) and the rtrim() feels a little
off.

Is string.join() preferred to ''.join? Does importing all of string
outweigh the readability of string.join()?

Any subversion geeks know of way to eliminate this code with a native
svn command?

Did other folks choke on generators for as long as I did? I'm not
going to admit, publicly, how long that was :) But I found this little
test illustrative:

def gen():
  yield 1
  yield 2
  yield 3

g = gen()
g.next()
 1
g.next()
 2
g.next()
 3
g.next()
 [stack trace]

Beyond simple, but the obviousness of it is hidden in many of the
examples I saw.
___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic? Building a full path from a visual file tree

[Kent Johnson]

stv wrote:
 I considered several brute-force solutions, but I persevered and came
 to, what I think, is a more Pythonic solution. What do you think?

Looks pretty sweet to me :-)
 
 import string
 
 def expand_tree(filetree):
   indent = '\t'
   stack = []
   for f in filetree:
 indents = f.count(indent)
 while len(stack)  indents: stack.pop()
 stack.append(f.strip())
 yield string.join(stack,'')
 if not f.endswith('/'): stack.pop()
 
 lines = [line.rstrip() for line in file('test.txt')]  
 for i in expand_tree(lines): print i
 
 Questions:
 
 Is the list comprehension the right idiom for getting a file into a
 list, without the EOL chars? I'm hard-pressed to see how it could be
 more concise, but this is Python :) and the rtrim() feels a little
 off.

The list comp is fine but I don't think you need it at all, since you 
strip() the string before you add it to stack.
 
 Is string.join() preferred to ''.join? Does importing all of string
 outweigh the readability of string.join()?

string.join() is deprecated, ''.join() is preferred.

Kent

___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic? Building a full path from a visual file tree

[stv]

 The list comp is fine but I don't think you need it
 at all, since you strip() the string before you
 add it to stack.

Ahh yes. I used the rstrip() in development, printing intermediary
output to stdout, so I could see what my input file-to-list looked
like (and it looked ugly with all those EOLs). The strip() to the
stack is there primarily to remove the indentation but, of course, it
can do double duty.


 string.join() is deprecated, ''.join() is preferred.


Well, I'll live with it ;-) fugly as it looks. I'm really finding that
Python nudges me into pleasant code. Doing the above in somthing like
VB, I would just brute-force it and it would feel right. Brute forcing
it in Python ... well, it just feels wrong  ... Thanks for the input.
___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Pythonic? Building a full path from a visual file tree

[stv]

On 3/21/06, stv [EMAIL PROTECTED] wrote:

 import string

 def expand_tree(filetree):
   indent = '\t'
   stack = []
   for f in filetree:
 indents = f.count(indent)
 while len(stack)  indents: stack.pop()
 stack.append(f.strip())
 yield string.join(stack,'')
 if not f.endswith('/'): stack.pop()

 The real-world solution will use a regex to find run
 of spaces at the start of element 'f'.

Hmmm, I'm having to rethink this ... regex will probably not do what I
want (count instance of indent ... or, even if regex will do,
there's probably a cleaner solution without it.

Given the subversion problem space (where I can count on 1 space for
each level of child-ness), are there cleaner solutions than this:

indents = len(f) - len(f.lstrip())
___
Tutor maillist  -  Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor