Re: Functional Programming and python

[Jussi Piitulainen]

Vito De Tullio writes:

> rusi wrote:
> 
> > [Not everything said there is correct; eg python supports currying
> > better [than haskell which is surprising considering that
> > Haskell's surname is [Curry!]
> 
> AFAIK python does not support currying at all (if not via some
> decorators or something like that).

I suppose rusi means functools.partial:

  >>> from functools import partial
  >>> trip = lambda x,y,z: (x,y,z)
  >>> partial(trip,'a','b')('c')
  ('a', 'b', 'c')

It also supports keyword arguments.

> Instead every function in haskell implicitly support currying...
> so... how does "no support" is better than "full support"?

Yes. I'm satisfied that Python does, but what can be seen as a
shortcoming in Haskell? Just curious.
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Re: Functional Programming and python

[rusi]

On Monday, September 23, 2013 11:54:53 PM UTC+5:30, Vito De Tullio wrote:
> rusi wrote:
> 
> > [Not everything said there is correct; eg python supports currying better
> > [than haskell which is surprising considering that Haskell's surname is
> > [Curry!]
> 
> 
> AFAIK python does not support currying at all (if not via some decorators or 
> something like that).
> 
> 
> Instead every function in haskell implicitly support currying... so... how 
> does "no support" is better than "full support"?

Without resorting to lambdas/new-functions:
 With functools.partial one can freeze any subset of a function(callable's) 
 parameters.
 
 In Haskell one can only freeze the first parameter or at most with a right 
section the second
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combine pictures

[andypu]

hello, i have a picture and i want to merge it with an other picture which is 
half transparent and the first picture will shine through it, has python the 
library's to do this?
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Re: Functional Programming and python

[Jussi Piitulainen]

rusi writes:

> Without resorting to lambdas/new-functions:
>  With functools.partial one can freeze any subset of a
>  function(callable's) parameters.
>
>  In Haskell one can only freeze the first parameter or at most with
>  a right section the second

You have an f of type A -> B -> C -> D -> E in Haskell, you can freeze
the first three parameters by calling it with three arguments. These
are equivalent:

f a b c d
(f a b c) d
(f a b) c d
(f a) b c d

So it's any initial sequence of arguments, not just the first.

And I thought such types were preferred over A * B * C * D -> E in
Haskell, so you tend to get this for free. Not sure of the syntax here
- it's been long since I did anything at all with Haskell.

A difference seems to be that in Python, a call can refer to named
parameters. This gives functools.partial some power over Haskell.

Another difference is that the value of functools.partial is always a
function that needs to be called with the remaining arguments, even if
there are none. Both the creation and the evaluation of the curried
functions just happens in Haskell.

(I also think that the word "currying" used to refer to what Haskell
does and it's an extension to use it to mean any partial evaluation.)
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How to login to a website using Python 3.x?

[Osumo Clement]

 Hi. I am new to Python. I am making a script where logging in to a website is 
the first step.. I am using Python 3.3 All of the help I have seen online uses 
urllib2 which in Python 3 aint there. I will greatly appreciate any help
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Re: How to login to a website using Python 3.x?

[Mark Lawrence]

On 24/09/2013 09:09, Osumo Clement wrote:

  Hi. I am new to Python. I am making a script where logging in to a website is 
the first step.. I am using Python 3.3 All of the help I have seen online uses 
urllib2 which in Python 3 aint there. I will greatly appreciate any help



urllib2 has been renamed in Python 3 see 
http://www.python.org/dev/peps/pep-3108/#urllib-package


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Mark Lawrence

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Re: combine pictures

[Terry Reedy]

On 9/24/2013 3:40 AM, and...@zoho.com wrote:

hello, i have a picture and i want to merge it with an other picture which is 
half transparent and the first picture will shine through it, has python the 
library's to do this?


Searching 'python image library' might lead one to
https://pypi.python.org/pypi/Pillow/2.1.0


--
Terry Jan Reedy

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removing BOM prepended by codecs?

[J. Bagg]

I'm having trouble with the BOM that is now prepended to codecs files. 
The files have to be read by java servlets which expect a clean file 
without any BOM.


Is there a way to stop the BOM being written?

It is seriously messing up my work as the servlets do not expect it to 
be there. I could delete it but that means another delay in retrieving 
the data. My work is a bibliographic system and I'm writing a new search 
engine in Python to replace an ancient one in C.


I'm working on Linux with a locale of en_GB.UTF8

--
Dr Janet Bagg
CSAC, Dept of Anthropology,
University of Kent, UK
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Re: python IDE and function definition

[Fabio Zadrozny]

On Mon, Sep 23, 2013 at 8:20 PM, Neil Hodgson  wrote:

> Chris Friesen:
>
>
>  where I could highlight the "stop" and ask it to go to the definition.
>> (Where the definition is in a different file.)
>>
>> I'm running into issues where my current IDE (I'm playing with Komodo)
>> can't seem to locate the definition, I suspect because it's too ambiguous.
>>
>
> Some IDEs allow you to help them understand the context by adding type
> information. Here's some documentation for Wing IDE that uses an isinstance
> assertion:
> http://www.wingware.com/doc/**edit/helping-wing-analyze-code


Just to note, PyDev can also use the assert isinstance as well as
docstrings (http://pydev.org/manual_adv_type_hints.html) for type hinting.

Cheers,

Fabio
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Re: removing BOM prepended by codecs?

[Steven D'Aprano]

On Tue, 24 Sep 2013 10:42:22 +0100, J. Bagg wrote:

> I'm having trouble with the BOM that is now prepended to codecs files.
> The files have to be read by java servlets which expect a clean file
> without any BOM.
> 
> Is there a way to stop the BOM being written?

Of course there is :-) but first we need to know how you are writing it 
in the first place.

If you are dealing with existing files, which already contain a BOM, you 
may need to open the files and re-save them without the BOM.

If you are dealing with temporary files you're creating programmatically, 
it depends how you're creating them. My guess is that you're doing 
something like this:

f = open("some file", "w", encoding="UTF-16")  # or UTF-32
f.write(data)
f.close()

or similar. Both the UTF-16 and UTF-32 codecs write BOMs. To avoid that, 
you should use UTF-16-BE or UTF-16-LE (Big Endian or Little Endian), as 
appropriate to your platform.

If you're getting a UTF-8 BOM, that's seriously weird. The standard UTF-8 
codec doesn't write a BOM. (Strictly speaking, it's not a Byte Order 
Mark, but a Signature.) Unless you're using encoding='UTF-8-sig', I can't 
guess how you're getting a UTF-8 BOM.

If you're doing something else, well, you'll have to explain what you're 
doing before we can tell you how to stop doing it :-)


> I'm working on Linux with a locale of en_GB.UTF8

The locale only sets the default encoding used by the OS, not that used 
by Python. Python 2 defaults to ASCII; Python 3 defaults to UTF-8.


-- 
Steven
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Re: removing BOM prepended by codecs?

[Peter Otten]

J. Bagg wrote:

> I'm having trouble with the BOM that is now prepended to codecs files.
> The files have to be read by java servlets which expect a clean file
> without any BOM.
> 
> Is there a way to stop the BOM being written?

I think if you specify the byte order explicitly with "UTF-16-LE" or 
"UTF-16-BE" no BOM is written.


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Re: Making it a MultiThread!

[Piet van Oostrum]

stas poritskiy  writes:

> Thanks for getting back to me, so i assume it is OK to have a very
> very long file? The sample code i posted here is basically the
> barebones of the main app.
> so, combining the GUI-file(gui.py) with main code is acceptable?
> Separating them into modules was initially the attempt to keep things
> in order.

Keeping things in separate modules is still OK. Just don't use circular
imports. Keeping the logic of your applcation and the GUI in separate
files is usually a good idea. And make sure the dependencies between the
modules are simple. Very, very long files usually are not a good idea.

Also you imported multiprocessing through anothe module. This obscures
the structure of the application, and is unnecesary. You should only
access a module through another module if you add a layer of abstraction
that makes it easier or more powerful.
-- 
Piet van Oostrum 
WWW: http://pietvanoostrum.com/
PGP key: [8DAE142BE17999C4]
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Re: How to send an anonymous mail via Python script

[Alister]

On Sat, 21 Sep 2013 20:41:25 +1000, Chris Angelico wrote:

> On Sat, Sep 21, 2013 at 8:15 PM, Νίκος  wrote:
>> On 21/9/2013 1:04 μμ, Chris Angelico wrote:
>>>
>>> On Sat, Sep 21, 2013 at 7:58 PM, Νίκος  wrote:

 Can you please tell me what alternation must be made in order to send
 this anonymously?

 that is my question. There must be a way.
>>>
>>>
>>> No, there isn't. The nearest you could come to anonymous mail would be
>>> sending via a botnet (to hide your IP address) and forging the from
>>> address. So unless you *want* your mail to be flagged as spam and
>>> detested by the entire world, NO THERE IS NO WAY to send it
>>> anonymously.
>>>
>>> ChrisA
>>>
>> How about an anonymous remailer then?
> 
> I'm going to spell this out for the benefit of anyone else who's reading
> this, because I know Nikos won't take any notice. This is a gross
> oversimplification, but I'm trying to condense everything into a single
> email.
> 


To put it even more simply
If you have a legitimate reason to send me emails then you have no 
legitimate reason to withhold your true Identity.

if you do I will assume you are a crook.

if you are asking for advise on how to achieve this I will assume you 
want to be a crook and will not provide any assistance.

-- 
No man would listen to you talk if he didn't know it was his turn next.
-- E.W. Howe
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Re: combine pictures

[Roy Smith]

In article ,
 Terry Reedy  wrote:

> On 9/24/2013 3:40 AM, and...@zoho.com wrote:
> > hello, i have a picture and i want to merge it with an other picture which 
> > is half transparent and the first picture will shine through it, has python 
> > the library's to do this?
> 
> Searching 'python image library' might lead one to
> https://pypi.python.org/pypi/Pillow/2.1.0

It might also lead one to

http://www.pythonware.com/products/pil/

That being said, I've had "Evaluate Pillow as possible PIL replacement" 
on my todo list for a while :-)
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Re: Functional Programming and python

[rusi]

On Tuesday, September 24, 2013 1:12:51 PM UTC+5:30, Jussi Piitulainen wrote:
> rusi writes:
> 
> > Without resorting to lambdas/new-functions:
> >  With functools.partial one can freeze any subset of a
> >  function(callable's) parameters.
> >
> 
> >  In Haskell one can only freeze the first parameter or at most with
> >  a right section the second
> 
> You have an f of type A -> B -> C -> D -> E in Haskell, you can freeze
> the first three parameters by calling it with three arguments. These
> are equivalent:
> 
> f a b c d
> (f a b c) d
> (f a b) c d
> (f a) b c d
> 
> So it's any initial sequence of arguments, not just the first.

Agreed. I missed that.

However as n increases there are n initial sequences (Haskell) whereas there 
are 2^n possible subsets (Python) (2^n - 1 if we remove the fully saturated 
case). So I would argue that Python syntax gives more flexibility in this 
direction than Haskell.  Add the further feature of **args and its even more

> 
> (I also think that the word "currying" used to refer to what Haskell
> does and it's an extension to use it to mean any partial evaluation.)

Hmm… Seems this is a contentious issue
http://en.wikipedia.org/wiki/Currying#Contrast_with_partial_function_application

which links to this LtU post that I find neat:

---
If I have a function f:(x,y)->z, I can't apply it to only one of its arguments. 
I can curry it, turning it into a function g:x->(y->z) ... and I can apply g to 
only one of the original arguments. But turning f into g and applying g to some 
x are technically different things.

I suspect the confusion arises because originally currying was a technique to 
model multiple-argument functions in a single-argument framework and was a 
meta-operation. In ML-like languages, the functions are typically already 
curried, so the only operation you see being done is partial application.
---
from http://lambda-the-ultimate.org/node/2266

-
Anyways thanks for that Ive added it to my 'lost-booty' list
http://blog.languager.org/2012/10/functional-programming-lost-booty.html#curry
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Re: How to send an anonymous mail via Python script

[Steven D'Aprano]

On Tue, 24 Sep 2013 11:36:16 +, Alister wrote:

> To put it even more simply
> If you have a legitimate reason to send me emails then you have no
> legitimate reason to withhold your true Identity.

"Dear Alister,

Forgive this anonymous email, but I don't wish to get fired from my job 
and sued for breaking the confidentiality agreement I signed, but 
somebody needs to speak out about this matter. You need to know that the 
company I work for, Acme Ltd, is illegally dumping radioactive waste in 
the street where you live in the form of extremely fine powder which 
blows all over the street, into your home and garden. Attached is the 
evidence for this, proving that knowledge of this dumping goes all the 
way to the company board. I suggest you talk to your lawyer before your 
children develop mutant superpowers, or possibly cancer, whichever 
happens first."


Whistleblower laws are useless. Sometimes people need to remain 
anonymous. Even when whistleblower laws have teeth, sometimes it's just 
better to keep your identity unknown.

However, in the specific case of Nikos, I cannot imagine any legitimate 
reason for him to be sending anonymous emails to his website users. I've 
asked him to explain, but he hasn't. I can only conclude that he is 
intending to send spam, or otherwise act unethically or even criminally. 
Even if I knew how to write an anonymous mail server, I wouldn't help him.



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Re: How to send an anonymous mail via Python script

[Chris Angelico]

On Tue, Sep 24, 2013 at 10:29 PM, Steven D'Aprano
 wrote:
> On Tue, 24 Sep 2013 11:36:16 +, Alister wrote:
>
>> To put it even more simply
>> If you have a legitimate reason to send me emails then you have no
>> legitimate reason to withhold your true Identity.
>
> "Dear Alister,
>
> Forgive this anonymous email, but I don't wish to get fired from my job
> and sued for breaking the confidentiality agreement I signed, but
> somebody needs to speak out about this matter.

There are definitely the odd times when a person needs anonymity. I do
not know of any times when an email-sending *computer* does. To send
your whistleblower email, I would recommend an HTTPS connection to
some free webmail service, or some sort of bouncer, or something - but
that bouncer can identify itself honestly to the receiver.

Same goes for other situations. I received your email, not from
pearwood.info, but from python.org - courtesy of Mailman. It's not
being sneaky about it, but the 'from' header is quite different from
the mail's actual origin. What I want to know here, primarily, is the
identity of the server who's giving me the message - ie python.org -
and MTAs will be adding tracking headers that identify that server.

(The concepts here are somewhat clouded by the c.l.py gateway, but
pick any other mailing list as your example and it'll be correct.)

ChrisA
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removing BOM prepended by codecs?

[J. Bagg]

I'm using:

outputfile = codecs.open (fn, 'w+', 'utf-8', errors='strict')

to write as I know that the files are unicode compliant. I run the raw 
files that are delivered through a Python script to check the unicode 
and report problem characters which are then edited. The files use a 
whole variety of languages from Sanskrit to Cyrillic and more obscure 
ones too.


I'll probably have to remove it in the servlet as we have standardised 
on utf-8. This was done some years ago when utf-16 was rare (apart from 
Macs).


J



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xml parsing as YML parser does does

[bab mis]

Hi ,
Here is an example how i do yml parsing and a proper pythonic object returns , 
is it possible in XML, tried lxml,dom, but there is no straight forward 
solution:

[root@linux-source pyrun]# cat x.yml
#Section for specifying test process information

Test: 

commoninfo: 
buildhome   : "/root/linuxbuilds"

 
Project:
default:

test_parameters:
svnuser: "vmbuild"
suite  : "sanity"
username   : "root"


Commands :
-   name   : generalcheck of destination
action : generalcheck

-   name   : retrieve source from svn
action : retsource
params : src=x,src1=y
[root@linux-source pyrun]



[root@linux-source pyrun]# cat a.py 
import yaml
fd = open("x.yml")
data = fd.read()
fd.close()
ydata = yaml.safe_load(data)
import pprint
pprint.pprint( ydata )

===


[root@linux-source pyrun]# python a.py 
{'Test': {'Project': {'default': {'Commands': [{'action': 'generalcheck',
'name': 'generalcheck of 
destination'},
   {'action': 'retsource',
'name': 'retrieve source from 
svn',
'params': 'src=x,src1=y'}],
  'test_parameters': {
  'suite': 'sanity',
  'svnuser': 'vmbuild',
  'username': 'root'}}},
  'commoninfo': {'buildhome': '/root/linuxbuilds'}}}
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Re: removing BOM prepended by codecs?

[Tim Golden]

On 24/09/2013 14:01, J. Bagg wrote:
> I'm using:
> 
> outputfile = codecs.open (fn, 'w+', 'utf-8', errors='strict')

Well for the life of me I can't make that produce a BOM on 2.7 or 3.4.
In other words:


import codecs
with codecs.open("temp.txt", "w+", "utf-8", errors="strict") as f:
  f.write("abc")

with open("temp.txt", "rb") as f:
  assert f.read()[:3] == b"abc"



works without any assertion failures on 2.7 and 3.4, both running on
Win7 and on 2.7 and 3.3 running on Linux.

Have I misunderstood your situation?

TJG
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Re: removing BOM prepended by codecs?

[Dave Angel]

On 24/9/2013 09:01, J. Bagg wrote:

Why would you start a new thread?  just do a Reply-List (or Reply-All
and remove the extra names) to the appropriate message on the existing
thread.

> I'm using:
>
> outputfile = codecs.open (fn, 'w+', 'utf-8', errors='strict')

That won't be adding a BOM.  It appends to an existing file, which
already may have a BOM in it.  Or conceivably you have a BOM in your
unicode string that you're passing to write() method.

>
> to write as I know that the files are unicode compliant. I run the raw 
> files that are delivered through a Python script to check the unicode 
> and report problem characters which are then edited. The files use a 
> whole variety of languages from Sanskrit to Cyrillic and more obscure 
> ones too.
>
it'd be much nicere to remove it when writing the file.
-- 
DaveA


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Re: What's the best way to extract 2 values from a CSV file from each row systematically?

[Alex Lee]

Thanks for the help guys! I'll definitely read up on the csv module 
documentation.

Tim, that's incredibly helpful, thanks a lot! :) My CSV file doesn't have 
headers, but I'm sure I can just as easily add it in manually.
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Re: combine pictures

[andypu]

Oh i thaught maybe python comes with something native, bevore i install 
something new i think i might better look into if kivy can do the job - thats 
allready installed...
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Re: Functional Programming and python

[Jussi Piitulainen]

rusi writes:
> On Tuesday, September 24, 2013 1:12:51 PM UTC+5:30, Jussi Piitulainen wrote:
> > rusi writes:
> > 
> > > Without resorting to lambdas/new-functions:
> > >  With functools.partial one can freeze any subset of a
> > >  function(callable's) parameters.
> > 
> > >  In Haskell one can only freeze the first parameter or at most
> > >  with a right section the second
> > 
> > You have an f of type A -> B -> C -> D -> E in Haskell, you can
> > freeze the first three parameters by calling it with three
> > arguments. These are equivalent:
> > 
> > f a b c d
> > (f a b c) d
> > (f a b) c d
> > (f a) b c d
> > 
> > So it's any initial sequence of arguments, not just the first.
> 
> Agreed. I missed that.

Ok.

> However as n increases there are n initial sequences (Haskell)
> whereas there are 2^n possible subsets (Python) (2^n - 1 if we
> remove the fully saturated case). So I would argue that Python
> syntax gives more flexibility in this direction than Haskell.

Strictly speaking and in principle, yes. I'm not sure how important
this is in practice: the positional parameter list should be short
anyway, Haskell does have the special mechanism for the second, and
there is always the fully general mechanism (lambda) in both languages
(and in another language I use that has neither built-in currying nor
keyword parameters :).

I agree that the ability to identify arguments by name gives a useful
amount of quite practical power, and I see that functools.partial uses
it nicely. So, no real disagreement on this from me.

Would the type system get in the way of providing some analogous
function in Haskell? I don't know.

> Add the further feature of **args and its even more
>
> > (I also think that the word "currying" used to refer to what
> > Haskell does and it's an extension to use it to mean any partial
> > evaluation.)
> 
> Hmm[] Seems this is a contentious issue
> http://en.wikipedia.org/wiki/Currying#Contrast_with_partial_function_application
> 
> which links to this LtU post that I find neat:

[snip]

Thanks. I don't think I have anything useful to add, though.
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Re: Help with python functions?

[Denis McMahon]

On Mon, 23 Sep 2013 19:40:47 -0700, kjakupak wrote:

> Not sure if we've gotten that far in class, considering I don't know how
> to go about doing that.

Which bit aren't you sure about?

(a) adding a "same unit" conversion to the units conversion program? 
(Actually, this bit isn't needed after all, you can avoid it with a test 
in comp.)

(b) calling temp from comp to establish a common unit?

(c) comparing the returned value of the call to temp with the other temp 
in comp

Question, given the original "temp" function as previously described by 
yourself, what does the following function "f" which takes the same params 
as "comp" do:

def f( t1, u1, t2, u2 ):
if u1 == u2:
return t2
else:
return temp( t2, u2, u1 )

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Re: How to send an anonymous mail via Python script

[Alister]

On Tue, 24 Sep 2013 12:29:14 +, Steven D'Aprano wrote:

> On Tue, 24 Sep 2013 11:36:16 +, Alister wrote:
> 
>> To put it even more simply If you have a legitimate reason to send me
>> emails then you have no legitimate reason to withhold your true
>> Identity.
> 
> "Dear Alister,
 
> 
> Whistleblower laws are useless. Sometimes people need to remain
> anonymous. Even when whistleblower laws have teeth, sometimes it's just
> better to keep your identity unknown.


That would be acceptable as an email to me as a company/gvt. officer.
emails to me as an individual have no justification in remaining anonymous
> 
> However, in the specific case of Nikos, I cannot imagine any legitimate
> reason for him to be sending anonymous emails to his website users. I've
> asked him to explain, but he hasn't. I can only conclude that he is
> intending to send spam, or otherwise act unethically or even criminally.
> Even if I knew how to write an anonymous mail server, I wouldn't help
> him.

indeed, I have given Nikos the benefit of the doubt & even tried to help 
him once when the question seemed within my limited abilities but without 
further information on the purpose I will not be helping with this one.#




-- 
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Selling cheaper than we do.
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Re: Help with python functions?

[Denis McMahon]

On Tue, 24 Sep 2013 03:15:23 +, Steven D'Aprano wrote:

> You don't have to use Kelvin. You could use any temperature scale, so
> long as it is the same for both temperatures.

Given that he already has a handy conversion function to call, he should 
be able to convert t2 into the units of t1 if they're in different units 
(2 lines), and then do his comparison (5 lines).

-- 
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Re: Functional Programming and python

[rusi]

On Tuesday, September 24, 2013 8:21:19 PM UTC+5:30, Jussi Piitulainen wrote:
> Would the type system get in the way of providing some analogous
> function in Haskell? I don't know.

Yes.
The haskell curry
curry f x y = f (x,y)
is really only curry2
curry3 would be
curry3 f x y z = f (x,y,z)
and so on upwards

Vanilla Haskell makes it real hard to put all these under one type umbrella

By comparison python's partial is quite effortless.

And this is an old conundrum in programming language design:

In C printf is easy to write and NOT put into the language but into external 
libraries
In Pascal, writeln cannot be outside the language because as a user defined 
function, its type would not fit the type system.

And so printf can be made to crash quite easily; not so writeln!
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Re: Functional Programming and python

[Chris Angelico]

On Wed, Sep 25, 2013 at 1:07 AM, rusi  wrote:
> And this is an old conundrum in programming language design:
>
> In C printf is easy to write and NOT put into the language but into external 
> libraries
> In Pascal, writeln cannot be outside the language because as a user defined 
> function, its type would not fit the type system.
>
> And so printf can be made to crash quite easily; not so writeln!

I assume you're talking about mismatching percent-markers and
arguments, there. That's because of a limitation in C's variadic
function support, ameliorated somewhat by gcc's warnings system, and
completely solved by other languages in which (s)printf can still be
an external function, but with reliable type checking. It's not
whether it's part of the language or not that does that.

ChrisA
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removing BOM prepended by codecs?

[J. Bagg]

I've checked the original files using od and they don't have BOMs.

I'll remove them in the servlet. The overhead is probably small enough 
unless somebody is doing a massive search. We have a limit anyway to 
prevent somebody stealing the entire set of data.


I started writing the Python search because the ancient C search had 
started putting out BOMs. I'm actually mystified because our home Linux 
box does not add BOMs even though it runs 2.7 but my work one does even 
though it has the same version. The only difference is Fedora 18 v 
Fedora 17.


The BOMs are certainly there:

<86> %R 10C0203z-621
%A François-Xavier Le_Bourdonnec

000 206 255 373   %   R   1   0   C   0   2   0   3   z   -

J

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Re: removing BOM prepended by codecs?

[Peter Otten]

J. Bagg wrote:

> I've checked the original files using od and they don't have BOMs.
> 
> I'll remove them in the servlet. The overhead is probably small enough
> unless somebody is doing a massive search. We have a limit anyway to
> prevent somebody stealing the entire set of data.
> 
> I started writing the Python search because the ancient C search had
> started putting out BOMs. I'm actually mystified because our home Linux
> box does not add BOMs even though it runs 2.7 but my work one does even
> though it has the same version. The only difference is Fedora 18 v
> Fedora 17.
> 
> The BOMs are certainly there:
> 
> <86> %R 10C0203z-621
> %A François-Xavier Le_Bourdonnec
> 
> 000 206 255 373   %   R   1   0   C   0   2   0   3   z   -
> 
> J
> 

Were these files edited with Notepad? According to

http://docs.python.org/2/library/codecs.html#encodings-and-unicode

"""
To increase the reliability with which a UTF-8 encoding can be detected, 
Microsoft invented a variant of UTF-8 (that Python 2.5 calls "utf-8-sig") 
for its Notepad program: Before any of the Unicode characters is written to 
the file, a UTF-8 encoded BOM (which looks like this as a byte sequence: 
0xef, 0xbb, 0xbf) is written.
"""

To strip off such a UTF-8 encoded BOM you can open the source file with 
"utf-8-sig" and write the output to a (different!) file with "utf-8"

with codecs.open(source, "r", encoding="utf-8-sig") as instream:
with codecs.open(dest, "w", encoding="utf-8") as outstream:
shutil.copyfileobj(instream, outstream)

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Re: Help with python functions?

[giacomo boffi]

kjaku...@gmail.com writes:

> def temp(T, from_unit, to_unit):
> conversion_table = {('c', 'k'):lambda x: x + 273.15,
> ('c', 'f'):lambda x: (x * (9.0/5)) + 32,
> ('k', 'c'):lambda x: x - 273.15,
> ('k', 'f'):lambda x: (x * (9.0/5)) - 459.67,
> ('f', 'c'):lambda x: (x - 32) * (5.0/9),
> ('f', 'k'):lambda x: (x + 459.67) * (5.0/9)}
> f = conversion_table[(from_unit.lower(), to_unit.lower())]
> return f(T)
>
> Would this be correct?

not always:

>>> temp(-300.0, 'c', 'k')
-26.8500023
>>> 


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  VS gli sciocchi puntigli di quel cretino del mio vicino
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Re: python IDE and function definition

[Travis Griggs]

On Sep 23, 2013, at 8:06 AM, Chris Friesen  wrote:

> 
> Hi all,
> 
> I'm looking for a python IDE (for Linux) that can look at code like this:
> 
> class ConductorManager(manager.Manager):
>def compute_recover(self, context, instance):
>self.compute_api.stop(context, instance, do_cast=False)
> 
> where I could highlight the "stop" and ask it to go to the definition. (Where 
> the definition is in a different file.)
> 
> I'm running into issues where my current IDE (I'm playing with Komodo) can't 
> seem to locate the definition, I suspect because it's too ambiguous.
> 
> The fact that python is dynamically typed seems to mean that there could 
> potentially be multiple answers, any class with a stop() method with the 
> right signature could presumably be plausible, right?  So rather than give 
> up, I'd like to have my IDE suggest all possible answers.

Hi Chris,

Not sure if this reproduces what you want or not. I use PyCharm (free for free 
stuff, and very affordable/worthwhile otherwise) on Linux (as well as 
OSX/Windows). I made a new project, added two files:

provider.py:

class Provider(object):
def stop(self):
pass

usage.py:

class Conglomerate(object):
def doSomething(self):
self.provision.stop()

I then highlight 'stop', hit Ctrl-B (menu option go to>>declarations) and it 
brings up all the stop() definitions it could find, the Provider one on the 
top, click it and I jump there. Ctrl-Alt-B (menu option for 
goto>>implementation(s)) does nothing… UNLESS… I add this method to 
Conglomerate:

def __init__(self):
super.__init__()
self.provision = Provider()

Then go to implementations takes me right there to the other file.

HTH
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Re: Help with python functions?

[MRAB]

On 24/09/2013 17:53, giacomo boffi wrote:

kjaku...@gmail.com writes:


def temp(T, from_unit, to_unit):
conversion_table = {('c', 'k'):lambda x: x + 273.15,
('c', 'f'):lambda x: (x * (9.0/5)) + 32,
('k', 'c'):lambda x: x - 273.15,
('k', 'f'):lambda x: (x * (9.0/5)) - 459.67,
('f', 'c'):lambda x: (x - 32) * (5.0/9),
('f', 'k'):lambda x: (x + 459.67) * (5.0/9)}
f = conversion_table[(from_unit.lower(), to_unit.lower())]
return f(T)

Would this be correct?


not always:


temp(-300.0, 'c', 'k')

-26.8500023





In other words, it depends what you mean by 'correct'.

Zero Kelvin ("Absolute Zero") is the lowest possible temperature; in
reality there's no such temperature as -300°C.

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Re: Functional Programming and python

[rusi]

On Tuesday, September 24, 2013 8:56:21 PM UTC+5:30, Chris Angelico wrote:
> On Wed, Sep 25, 2013 at 1:07 AM, rusi  wrote:
> > And this is an old conundrum in programming language design:
> >
> > In C printf is easy to write and NOT put into the language but into 
> > external libraries
> 
> > In Pascal, writeln cannot be outside the language because as a user defined 
> > function, its type would not fit the type system.
> >
> > And so printf can be made to crash quite easily; not so writeln!
> 
> I assume you're talking about mismatching percent-markers and
> arguments, there. That's because of a limitation in C's variadic
> function support, ameliorated somewhat by gcc's warnings system, and
> completely solved by other languages in which (s)printf can still be
> an external function, but with reliable type checking. It's not
> whether it's part of the language or not that does that.

Sure there can be and are specific workarounds.

My point was a general one:
Strong type system: Some desirable programs will get kicked out
Weak type system: Some undesirable programs will slip in
'Exactly' correct type system: Impossible by halting problem 
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Re: python, pythontex and plots

[Piet van Oostrum]

chitt...@uah.edu writes:

> True, I did not explain what I was trying to do.
>
> pythontex is a package that allows the inclusion of python code within a
> LaTeX document - (sort of like python.sty, but IMO, better) - I use
> it along with noweb to create documents that contain documentation,
> code and output of the code - and pythontex allows me to access variables
> within the python code embedded in the LaTeX - except for the case
> I mentioned ... Within the python code (inside the LaTeX document) I had
> a "savefig(outputfile)" and I was trying to reference the outputfile
> using \py{outputfile}

It could be that \includegraphics needs an expandable TeX form for its
filename, and \py probably isn't. I haven't tried pythontex yet (I
didn't know about it before your posting), so I can only guess. I am
going to try it out later. But if I am correct then the following might
work:

\newcommand{\filename}{}
\edef\filename{\py{outputfile}}

\includegraphics[scale=0.75]{\filename}

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Re: removing BOM prepended by codecs?

[wxjmfauth]

Le mardi 24 septembre 2013 11:42:22 UTC+2, J. Bagg a écrit :
> I'm having trouble with the BOM that is now prepended to codecs files. 
> 
> The files have to be read by java servlets which expect a clean file 
> 
> without any BOM.
> 
> 
> 
> Is there a way to stop the BOM being written?
> 
> 
> 
> It is seriously messing up my work as the servlets do not expect it to 
> 
> be there. I could delete it but that means another delay in retrieving 
> 
> the data. My work is a bibliographic system and I'm writing a new search 
> 
> engine in Python to replace an ancient one in C.
> 
> 
> 
> I'm working on Linux with a locale of en_GB.UTF8
> 
> 
> 
> -- 
> 
> Dr Janet Bagg
> 
> CSAC, Dept of Anthropology,
> 
> University of Kent, UK

-

Some points.

- The coding of a text file does not matter. What's
count is the knowledge of the coding.

- The *mark* (once the Unicode.org terminology in FAQ) indicating
a unicode encoded raw text file is neither a byte order mark,
nor a signature, it is an encoded code point, the encoded
U+FEFF, 'ZERO WIDTH NO-BREAK SPACE', code point. (Note, a
non breaking space at the start of a text is a non sense.)

- When such a mark exists, it is always possible to work
100% safely. No possible error.

- When such a mark does not exist, in many cases only
guessing is a (the) valid solution.

These are facts.


Now to the question, should I use (put) such a mark,
esp. in utf-8? I would say the following:

It seems to me, one see more and more marked utf-8 files.
(Windows is probably a reason.)

More importantly, more and more tools and software are
handling this utf-8 mark, or are corrected to support it,
so it basicaly does not hurt too much. Eg. Python, golang 1.1
(was not the case in 1.0), LibreOffice, TeXWorks supports it
now (was once not the case), the unicode TeX engines, ...

If I had to work in "archiving", it would seriously think
twice.

PS Unicode encodes characters on a per *script* ("alphabet")
basis, not per *language*.

jmf

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removing BOM prepended by codecs?

[J. Bagg]

My editor is JEdit. I use it on a Win 7 machine but have everything set 
up for *nix files as that is the machine I'm normally working on.


The files are mailed to me as updates. The library where the indexers 
work do use MS computers but this is restricted to EndNote with an 
exporter into the old Bib-Refer format which we use. I then run them 
through a Python program to check the unicode for new characters that 
also creates an ascii transliteration of the main fields and checks for 
errors.


The problem is occuring at the search stage. This stage creates a script 
with directives to search particular years and then puts the results 
into a file in /tmp. The process is left over from an old CGI version 
but is efficient and so has been kept. This has been done with a very 
old C program that a collegue wrote back in the 90s with more recent 
updates. I'm in the process of updating this to Python as it is getting 
too difficult to maintain.


J
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Re: Help with python functions?

[Denis McMahon]

On Tue, 24 Sep 2013 14:51:31 +, Denis McMahon wrote:

> Question, given the original "temp" function as previously described by
> yourself, what does the following function "f" which takes the same
> params as "comp" do:
> 
> def f( t1, u1, t2, u2 ):
> if u1 == u2:
> return t2
> else:
> return temp( t2, u2, u1 )

Hmm, maybe:

if u1 == u2:

should have been:

if u1.lower() == u2.lower():

-- 
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Re: removing BOM prepended by codecs?

[Chris Angelico]

On Wed, Sep 25, 2013 at 4:43 AM,   wrote:
> - The *mark* (once the Unicode.org terminology in FAQ) indicating
> a unicode encoded raw text file is neither a byte order mark,
> nor a signature, it is an encoded code point, the encoded
> U+FEFF, 'ZERO WIDTH NO-BREAK SPACE', code point. (Note, a
> non breaking space at the start of a text is a non sense.)
>
> - When such a mark exists, it is always possible to work
> 100% safely. No possible error.

I have a file encoded in Latin-1 which begins with LATIN SMALL LETTER
Y WITH DIAERESIS followed by LATIN SMALL LETTER THORN. I also have a
file encoded in EBCDIC (okay, I don't really, but let's pretend) that
begins with the same bytes. But of course, when such a mark exists,
there is no possible error - of that there is no manner of doubt, no
possible, probable shadow of doubt, no possible doubt whatever.

("No possible doubt whatever.")

ChrisA
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Re: removing BOM prepended by codecs?

[Piet van Oostrum]

"J. Bagg"  writes:

> I've checked the original files using od and they don't have BOMs.
>
> I'll remove them in the servlet. The overhead is probably small enough
> unless somebody is doing a massive search. We have a limit anyway to
> prevent somebody stealing the entire set of data.
>
> I started writing the Python search because the ancient C search had
> started putting out BOMs. I'm actually mystified because our home Linux
> box does not add BOMs even though it runs 2.7 but my work one does even
> though it has the same version. The only difference is Fedora 18 v
> Fedora 17.
>
> The BOMs are certainly there:
>
> <86> %R 10C0203z-621
> %A François-Xavier Le_Bourdonnec
>
> 000 206 255 373   %   R   1   0   C   0   2   0   3   z   -
>
That is not a BOM or SIG. It isn't even valid utf-8.
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