date:20150116


Ian Kelly wrote:

Wait, are you actually asking why bool is a doubleton? If nobody has
answered that, I think probably nobody understood you were asking it,
because it shouldn't need to be explained.


What does perhaps need explaining is why Python goes
out of its way to *enforce* the doubleton-ness of bool.

I don't know all of Guido's reasoning on this, but part
of it is probably to do with implementation efficiencies.
There are several places in the CPython source where it's
assumed that, if an object is known to be of type bool,
then its truth or falseness can be determined with a
pointer comparison.

--
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Re: List of python -m tools

2015-01-16 Thread Miki Tebeka

Thanks for all the answers!
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EuroPython 2015: Your chance to sign up as a launch sponsor

2015-01-16 Thread M.-A. Lemburg

Companies who would like to sign up as a EuroPython 2015 launch sponsor
are encouraged to contact the sponsor work group at:

sponsor...@europython.eu

Launch sponsors will get the additional benefit of being listed on the
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Re: Comparisons and sorting of a numeric class....


Andrew Robinson wrote:


I never said subclassing bool is the 'only' solution; I 
have indicated it's a far better solution than many.


An assertion with which we very much disagree.

I have spent well over 
twenty years on and off dealing with boolean values that are very often 
mixed indistinguishably with 'don't care' or 'tri-state' or 'metastable 
states'.


I think you're overestimating how useful it will be to
pass one of your extended boolean values to existing
code expecting a plain boolean.

The purpose of the bool type in Python and other languages
is for making control-flow decisions. When you hit

   if x:
  do_something()
   else:
  do_something_else()

and x is Undefined or TriState or 47% true, what is
supposed to happen? The right thing to do will depend on
the circumstances, so you're going to need custom code
for dealing with those values.

I'm not even sure it's right to single out two of the
extended values as corresponding to True and False in
all cases. It may seem obvious that the high state
of a digital logic signal should be True and the low
state should be False, but -- what about active-low
signals? They use the opposite convention!

Then I look at python development historically and look at the built in 
class's return values for compares; and I notice; they have over time 
become more and more tied to the 'type' bool.


Actually, it's the opposite. Originally, all the comparison
operators got funneled through a single special method __cmp__,
which was required to return a negative, zero or positive
integer; hard-coded logic in the interpreter then derived a
boolean from that.

When rich comparisons were introduced (i.e. the ability to
override all the comparison operators individually), that
restriction was lifted.

I expect sometime in the 
future that python may implement an actual type check on all comparison 
operators so they can not be used to return anything but a bool.


That's not going to happen. If nothing else, it would
break NumPy, which compares arrays element-by-element and
returns an array of booleans.

I already noticed a type check on the return value of len() so that I 
can't return infinity, even when a method clearly is returning an 
infinitely long iterator


That's acknowledged as being less than desirable, but
fixing it would have performance implications, as well as
breaking the C extension API.

It's not really much of a limitation, anyway. Iterators
don't actually have a __len__; they can optionally have a
__length_hint__ method, but infinite iterators can just
leave that undefined.

That suggests to me that there is significant risk in python of having 
type checking on all __xx__ methods in the future.


You need have no fear of that. The trend has actually
been towards *less* restrictions on return types, and
I can't imagine that changing.


- use delegation to proxy True and False;


That sounds like a far more likely to succeed alternative, and is one of 
a handful of alternatives I have been exploring on my own.


A proxy is still a different type. Whether you use a
proxy or a completely new type for this is entirely a
matter of implementation convenience. You won't magically
gain any capabilities that you couldn't have implemented
otherwise.

python may not be able to do it 
totally from the python side because there is a difference in how Python 
handles type() checks and isinstance() checks.


There's no way I know of to make type() lie about the
true type of an object, proxy or not. But that would only
be a problem for code relying on type(x) is bool, which
I expect to be extremely rare if it exists at all.

Though I DO want to point out that Charles Bool did not invent the 
computer,


That's correct, because he didn't exist. :-) Boolean algebra
is named after George Boole. You're probably thinking of
Charles Babbage, who design (although never fully implemented)
what could be regarded as the first general purpose programmable
computer.

Name recognition is great for honoring a man -- but makes for a poor 
reason to choose a strict implementation of bool.


This is utter nonsense. The strict implementation of
bool you speak of isn't chosen to honour George Boole.

It's chosen because it's perfectly suited for its intended
application of flow-control in programming -- which is the
vast majority of the use of logic *above* the hardware
level. And since it happens to be a true Boolean algebra,
the name is entirely appropriate.


And those truth tables are not part of Boolean algebra.


Oh wow I never expected to hear that --  But I guess you were never 
trained to do boolean algebra, formally ?


A Boolean algebra is a mathematical structure with a precise
definition. There exist Boolean algebras with more than two
values, but the don't-care states found in data sheets don't
fit into any of them. The data sheets call them truth tables,
not Boolean algebra tables. :-)

The truth tables on data sheets are VERY VERY much intended

Re: lambdak: multi-line lambda implementation in native Python


Dennis Lee Bieber wrote:

On Fri, 16 Jan 2015 01:50:00 +1100, Chris Angelico ros...@gmail.com
declaimed the following:



Problem: You have a smartphone with a 4x4 pixel screen.


BIG problem, considering that a late 70s DECWriter needed 5x7 pixels
for glyphs in an 8x10 pixel character cell {as I recall...}


If those are 24-bit RGB pixels, you could encode
3 characters in each pixel.

You'd need eyes with rather good colour perception
to read it, though.

--
Greg
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Re: Comparisons and sorting of a numeric class....

On Friday, January 16, 2015 at 7:20:13 AM UTC+5:30, Andrew Robinson wrote:
snipped 542 lines

Disclaimers 
1. Ive not really read the above 542 lines and earlier
2. I am not a fan of OOP

Still some thoughts...

Electrical engineering (EE) and computer science (CS) may seem related
but are quite different disciplines. In fact there is some amount of
'client-supplier' in this relation - you folks make the machines we use.

Now one of the basic things that needs to be effected to make this transition
is the so-called digital abstraction

To start with we say (say) that 0V is 0-logic, 3.3V is 1-logic.
But that's hardly enough, we need margins, forbidden regions, Postel's law
etc.  This mapping is hardly straightforward. And that is still the
'static-discipline'.

When time comes in we need to deal with the fact that when a gate
switches it will willy-nilly go through the forbidden region.  From here
we have to go through/into clock disciplines, delay insensitie circuits etc.

Should CS-ists deal with all this??
If you say yes then what are you EE-guys doing?
If no then you are agreeing with all the others here.

In some more detail:
You seem to want a multi-valued logic. How many values?
There are quite a few answers:

- 4 -- {0,1,Z,X} - http://en.wikipedia.org/wiki/Four-valued_logic
- 9 -- above + weak drives http://en.wikipedia.org/wiki/IEEE_1164

And probably half a dozen others.

You say you REALLY NEED these in your work.
Yes, many people need many things, eg.

1. Mars orbiter was lost due to a mismatch of MKS and FPS systems
http://edition.cnn.com/TECH/space/9909/30/mars.metric.02/

Does that make a case for building in units into programming languages?

2. C.A.R Hoare said the invention of the null-pointer was a billion-dollar
mistake. Do C programmers agree with him?

3. He also considered exception handling as a terrible disaster since it
confuses flow of control.  Are python (or most modern language) users likely
to agree?

All these are instances of a basic principle that Niklaus Wirth enunciated:
The most important decision of a language designer are what to leave out
of the language.

Finally in python 3.4 onwards there are enums. You can do this

 from enum import IntEnum

 class Bool4(IntEnum):
...   F=0
...   T=1
...   Z=2
...   X=3
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Re: lambdak: multi-line lambda implementation in native Python

2015-01-16 Thread Marko Rauhamaa

Gregory Ewing greg.ew...@canterbury.ac.nz:

 Dennis Lee Bieber wrote:
 On Fri, 16 Jan 2015 01:50:00 +1100, Chris Angelico ros...@gmail.com
 declaimed the following:

Problem: You have a smartphone with a 4x4 pixel screen.

  BIG problem, considering that a late 70s DECWriter needed 5x7
 pixels for glyphs in an 8x10 pixel character cell {as I recall...}

 If those are 24-bit RGB pixels, you could encode
 3 characters in each pixel.

Not since Python3. Characters are Unicode now so you'll need to dedicate
a pixel for each character.


Marko
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How to wow someone new to Python

Scenario: You're introducing someone to Python for the first time.
S/he may have some previous programming experience, or may be new to
the whole idea of giving a computer instructions. You have a couple of
minutes to show off how awesome Python is. What do you do?

I was thinking along the lines of a simple demo in the REPL, showing
off some of Python's coolest features. But then I got stuck on the
specifics. What are Python's best coolnesses? What makes for a good
demo?

Ideally, this should be something that can be demo'd quickly and
easily, and it should be impressive without going into great details
of and see, this is how it works on the inside. So, how would you
brag about this language?

ChrisA
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Re: How to wow someone new to Python

2015-01-16 Thread Skip Montanaro

If you want to show off the REPL, I'd got for iPython and show them some
simple matplotlib examples (plotting sin waves, maybe dig up a CSV file on
the net with some data your friend is familiar with, etc)

Skip


On Fri, Jan 16, 2015 at 9:03 AM, Chris Angelico ros...@gmail.com wrote:

 Scenario: You're introducing someone to Python for the first time.
 S/he may have some previous programming experience, or may be new to
 the whole idea of giving a computer instructions. You have a couple of
 minutes to show off how awesome Python is. What do you do?

 I was thinking along the lines of a simple demo in the REPL, showing
 off some of Python's coolest features. But then I got stuck on the
 specifics. What are Python's best coolnesses? What makes for a good
 demo?

 Ideally, this should be something that can be demo'd quickly and
 easily, and it should be impressive without going into great details
 of and see, this is how it works on the inside. So, how would you
 brag about this language?

 ChrisA
 --
 https://mail.python.org/mailman/listinfo/python-list

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Re: How to wow someone new to Python

2015-01-16 Thread Andrew Berg

On 2015.01.16 09:03, Chris Angelico wrote:
 Scenario: You're introducing someone to Python for the first time.
 S/he may have some previous programming experience, or may be new to
 the whole idea of giving a computer instructions. You have a couple of
 minutes to show off how awesome Python is. What do you do?
 
 I was thinking along the lines of a simple demo in the REPL, showing
 off some of Python's coolest features. But then I got stuck on the
 specifics. What are Python's best coolnesses? What makes for a good
 demo?
 
 Ideally, this should be something that can be demo'd quickly and
 easily, and it should be impressive without going into great details
 of and see, this is how it works on the inside. So, how would you
 brag about this language?
If the person is already familiar with programming, you could show off how
Python doesn't do a best effort guess at what to do when you make a mistake
(explicit is better than implicit). Many other languages will, for example,
make an undefined variable into a variable defined as an empty string or allow
silly things like 5 + cheese, whereas Python will let you know that you made
a mistake somewhere instead of letting garbage propagate. This behavior can be
frustrating for newbies to Python, but with someone there to explain why it
works that way, they can learn to appreciate it instead of giving up in anger
after Python keeps throwing exceptions at them.

If the person is not familiar with programming, show them how easy it is to get
something useful written quickly, even with only the stdlib. Low-level details
are handled so that you can focus on what you want the program to do, and there
is a ton of stuff in the stdlib so that it's likely you don't need to go
searching for a bunch of different libraries so that again, you can focus what
you want the program to do. For this, chances are, that person has some things
in mind already that are not difficult to get started with using Python. Also,
using the REPL for this makes it an even better demo. You can probably have the
basic functionality of whatever cool thing they want right there in the REPL.
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Re: How to wow someone new to Python

2015-01-16 Thread Marko Rauhamaa

Chris Angelico ros...@gmail.com:

 Scenario: You're introducing someone to Python for the first time.
 S/he may have some previous programming experience, or may be new to
 the whole idea of giving a computer instructions. You have a couple of
 minutes to show off how awesome Python is. What do you do?

My experience is that if you have your customer try their hand on
programming and complete a simple challenge, they'll be extremely
impressed. Did I manage that?

On the other hand, if you want to demo your greatest achievements at the
screen, they will be left unmoved. Even my favorite Zynga game looks
cooler than that.

 I was thinking along the lines of a simple demo in the REPL, showing
 off some of Python's coolest features. But then I got stuck on the
 specifics. What are Python's best coolnesses? What makes for a good
 demo?

I would advise steering clear of the REPL and go directly to writing a
program and executing it. Maybe the classic ASCII graphics presentation
of the sine wave:


#!/usr/bin/env python3

import time
import math

def main():
for angle in range(0, 10, 5):
print(int((1 + math.sin(math.radians(angle))) * 35) * *)
time.sleep(0.1)

if __name__ == __main__:
main()


 Ideally, this should be something that can be demo'd quickly and
 easily, and it should be impressive without going into great details
 of and see, this is how it works on the inside. So, how would you
 brag about this language?

I'd recommend not skipping the traditional boilerplate (see my example).
Be professional from the start.


Marko
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Re: lambdak: multi-line lambda implementation in native Python

2015-01-16 Thread Michael Torrie

On 01/15/2015 10:29 PM, Ian Kelly wrote:
 On Thu, Jan 15, 2015 at 9:00 PM, Chris Angelico ros...@gmail.com wrote:
 My first response was going to be Well, you can always add another
 layer of indirection to try to solve your problem, but then I went
 and looked up builders on Wikipedia. Now I'm confused. What can you do
 with a builder that you can't do with a constructor?
 
 In Java you have to write a separate constructor for every conceivable
 combination of arguments. If there are a lot of optional arguments,
 that's an exponentially large number of constructors. The builder
 pattern provides a solution to that problem.
 
 In Python you just have one initializer with defaults for the optional
 arguments, so it's not an issue.

Which seems to confirm my understanding that these patterns are in large
part a response to limitations in the language, which certainly doesn't
engender a fondness for the Java.

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Re: How to wow someone new to Python

2015-01-16 Thread Marco Buttu


On 16/01/2015 16:03, Chris Angelico wrote:

Scenario: You're introducing someone to Python for the first time.
S/he may have some previous programming experience, or may be new to
the whole idea of giving a computer instructions. You have a couple of
minutes to show off how awesome Python is. What do you do?


The batteries included: some useful and simple examples with only core 
data type objects, built-in functions and standard library


--
Marco Buttu

INAF-Osservatorio Astronomico di Cagliari
Via della Scienza n. 5, 09047 Selargius (CA)
Phone: 070 711 80 217
Email: mbu...@oa-cagliari.inaf.it

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Re: How to wow someone new to Python

On Friday, January 16, 2015 at 8:34:20 PM UTC+5:30, Chris Angelico wrote:
 Scenario: You're introducing someone to Python for the first time.
 S/he may have some previous programming experience, or may be new to
 the whole idea of giving a computer instructions. You have a couple of
 minutes to show off how awesome Python is. What do you do?

There is this story -- maybe apocryphal -- that the tendency to vote
democratic or republican runs so deep it can be detected from 
genetic markers.

Similar things apply to programming:
Some people are drawn to a mathematical style; some are not
Some people love cute little scripts; some are left cold
Some love graphics; some dislike
etc etc
All corollary to:
Some people can think like programmers; most cant
[Who does the last quote? Steve Jobs?]

So to start with, you need to 'fingerprint' (is that the word?)
your subject.

 
 I was thinking along the lines of a simple demo in the REPL, showing
 off some of Python's coolest features. But then I got stuck on the
 specifics. What are Python's best coolnesses? What makes for a good
 demo?

The reason I find the REPL particularly cool for such demos
[I am surprised that Marko doesn't]
is that at least to some extent you can straddle some of the
divides above.

How about a little web-scrape with beautiful-soup?
Followed by maybe a throw the results into a csv-file
and open in the local spreadsheet?

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Re: How to wow someone new to Python

2015-01-16 Thread Mirage Web Studio


On 01/16/2015 08:33 PM, Chris Angelico wrote:
 Scenario: You're introducing someone to Python for the first time.
 S/he may have some previous programming experience, or may be new to
 the whole idea of giving a computer instructions. You have a couple of
 minutes to show off how awesome Python is. What do you do?

 I was thinking along the lines of a simple demo in the REPL, showing
 off some of Python's coolest features. But then I got stuck on the
 specifics. What are Python's best coolnesses? What makes for a good
 demo?

 Ideally, this should be something that can be demo'd quickly and
 easily, and it should be impressive without going into great details
 of and see, this is how it works on the inside. So, how would you
 brag about this language?

 ChrisA

hello,

I am a newbie to python, I have dwelled in c,qt none in java. php a lot,
though I don't make money with any of those.

The best thing I find is python is very easy, the best part maybe
because of my inexperience with other languages are the List and Dict
data types that just solved problems I had in real life made solvable
with python very easily. when I had to worry about memory and pointers
to memory in those other languages, python just made me focus on the
solution I want. also the way I can read python program just like they
are written in plain eglish :)

a personal problem I tried to solve is that how many characters  exist
in  a sequence statistically (with 2 or more characters in len)  in any
given file and then their count.  For a 100kb file I used practially all
programming knowledge in from the other languages but failed miserably
as the computation were taking more time with each bigger chunck of
file. I would have to do a lot of memery management with python using
those style like deleting list and dict before adding another. but when
I tried to solve the problem natively with python it just took a blink
of an eye for them to solve upto 50kb file. but for larger files
although instant it is just memory consuming since I was limit with 2 gb
I ddin't poke further.

this was my exp and I find programming fun in python like ironman
talking to jarvis

keep computing!!!

GCM
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Re: How to wow someone new to Python

2015-01-16 Thread Albert-Jan Roskam



On Fri, Jan 16, 2015 4:24 PM CET Andrew Berg wrote:

On 2015.01.16 09:03, Chris Angelico wrote:
 Scenario: You're introducing someone to Python for the first time.
 S/he may have some previous programming experience, or may be new to
 the whole idea of giving a computer instructions. You have a couple of
 minutes to show off how awesome Python is. What do you do?
 
 I was thinking along the lines of a simple demo in the REPL, showing
 off some of Python's coolest features. But then I got stuck on the
 specifics. What are Python's best coolnesses? What makes for a good
 demo?
 
 Ideally, this should be something that can be demo'd quickly and
 easily, and it should be impressive without going into great details
 of and see, this is how it works on the inside. So, how would you
 brag about this language?
If the person is already familiar with programming, you could show off how
Python doesn't do a best effort guess at what to do when you make a mistake
(explicit is better than implicit). Many other languages will, for example,
make an undefined variable into a variable defined as an empty string or allow
silly things like 5 + cheese, whereas Python will let you know that you made
a mistake somewhere instead of letting garbage propagate. This behavior can be
frustrating for newbies to Python, but with someone there to explain why it
works that way, they can learn to appreciate it instead of giving up in anger
after Python keeps throwing exceptions at them.

If the person is not familiar with programming, show them how easy it is to get
something useful written quickly, even with only the stdlib

Completely agree! Find out that person's itch and make a scratch.py that shows 
how problem-oriented the language is, with code that somewhat reads like 
regular English. REPL will also work, if you prepare it well enough. Ipython 
Notebook!


Low-level details
are handled so that you can focus on what you want the program to do, and there
is a ton of stuff in the stdlib so that it's likely you don't need to go
searching for a bunch of different libraries so that again, you can focus what
you want the program to do. For this, chances are, that person has some things
in mind already that are not difficult to get started with using Python. Also,
using the REPL for this makes it an even better demo. You can probably have the
basic functionality of whatever cool thing they want right there in the REPL.
-- 
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Re: How to wow someone new to Python

On Friday, January 16, 2015 at 10:51:52 PM UTC+5:30, Mirage Web Studio wrote:
 On 01/16/2015 08:33 PM, Chris Angelico wrote:
  Scenario: You're introducing someone to Python for the first time.
  S/he may have some previous programming experience, or may be new to
  the whole idea of giving a computer instructions. You have a couple of
  minutes to show off how awesome Python is. What do you do?
 
  I was thinking along the lines of a simple demo in the REPL, showing
  off some of Python's coolest features. But then I got stuck on the
  specifics. What are Python's best coolnesses? What makes for a good
  demo?
 
  Ideally, this should be something that can be demo'd quickly and
  easily, and it should be impressive without going into great details
  of and see, this is how it works on the inside. So, how would you
  brag about this language?
 
  ChrisA
 
 hello,
 
 I am a newbie to python, I have dwelled in c,qt none in java. php a lot,
 though I don't make money with any of those.
 
 The best thing I find is python is very easy, the best part maybe
 because of my inexperience with other languages are the List and Dict
 data types that just solved problems I had in real life made solvable
 with python very easily. when I had to worry about memory and pointers
 to memory in those other languages, python just made me focus on the
 solution I want. 

Nice point!
First class concrete data structures is a blessing especially for
a C programmer.

Here is an old Guido workout of dicts
https://www.python.org/doc/essays/graphs/

Probably can be improved to use comprehensions
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Re: How to wow someone new to Python

On Sat, Jan 17, 2015 at 4:31 AM, Rustom Mody rustompm...@gmail.com wrote:
 Nice point!
 First class concrete data structures is a blessing especially for
 a C programmer.

Definitely! Worth noting.

There've been some nice concepts mentioned; concrete suggestions would
be good too. Some specific feature or exact line of code that would
show off Python's awesomeness.

ChrisA
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recursive function: use a global or pass a parameter?

2015-01-16 Thread Tim

I have this type of situation and wonder if I should use a global variable 
outside the recursive function instead of passing the updated parameter 
through. 

I want to get a union of all the values that any 'things' key may have, even in 
a nested dictionary (and I do not know beforehand how deep the nesting might 
go):

d = {'things':1, 'two':{'things':2}}

def walk(obj, res):
if not hasattr(obj, 'keys'):
return set(), set()

if 'things' in obj:
res.add(obj['things'])

for k in obj:
walk(obj[k], res)

return res

walk(d, set()) # returns {1, 2}

Is it better to use a global to keep track of the values or does it even matter?

thanks,
--Tim
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Re: recursive function: use a global or pass a parameter?

On Sat, Jan 17, 2015 at 4:49 AM, Tim jtim.arn...@gmail.com wrote:
 I want to get a union of all the values that any 'things' key may have, even 
 in a nested dictionary (and I do not know beforehand how deep the nesting 
 might go):

 d = {'things':1, 'two':{'things':2}}

 def walk(obj, res):
 if not hasattr(obj, 'keys'):
 return set(), set()

 if 'things' in obj:
 res.add(obj['things'])

 for k in obj:
 walk(obj[k], res)

 return res

 walk(d, set()) # returns {1, 2}

 Is it better to use a global to keep track of the values or does it even 
 matter?

I would use a parameter rather than a global, but I'd make the
parameter optional:

def all_keys(obj, accum=None):
if accum is None: accum=set()
if 'things' in obj:
res.add(obj['things'])
for val in obj.values():
all_keys(val, accum)
return all_keys

ChrisA
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Re: How to wow someone new to Python

2015-01-16 Thread Tim Chase

On 2015-01-17 02:03, Chris Angelico wrote:
 Ideally, this should be something that can be demo'd quickly and
 easily, and it should be impressive without going into great details
 of and see, this is how it works on the inside. So, how would you
 brag about this language?

First, I agree with Andrew Berg's suggestion about the breadth of the
stdlib.  This always irks me when I have to return to the C/C++
world where there's no standard library for things like networking
(and thus no stock libraries for IMAP, SMTP, HTTP, FTP, etc or
email-message handling), CSV processing, regular expressions,
zip/tar/zlib files, SHA1/MD5, command-line option processing,
threading, and no available-everywhere GUI.  In the Java world, it
feels like much of this is available, but that the glommed-on
standards have multiple ways to do them (the old way(s) and the
new/improved way).  In PHP, well...that's just PHP (difficult-to-grok
equality testing, inconsistent naming conventions and parameter
ordering, lack of namespacing, easy-to-screw-up string interpolation,
hacky OOP, etc).

My fast-introduction go-to items are dir() and help() within the REPL
interface.  Nothing speeds up my development like being able to
drop to a PDB prompt and inspect an object, ask what properties it
supports, dump them, get help on them, etc.

There's also the bigint stuff that means I don't have to worry about
over/underflow errors.

I'm sure there are more great ideas, but how you market might depend
on your audience's background in programming (what language did they
use and what pain-points did they experience).

-tkc


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Re: How to wow someone new to Python

2015-01-16 Thread Emile van Sebille


On 1/16/2015 9:44 AM, Chris Angelico wrote:
snip
 exact line of code that would

show off Python's awesomeness.



a,b = b,a


Emile


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Android Native Build Help: python build_ext

2015-01-16 Thread Cyd Haselton

I'm building python on my Android tablet and, while the executable and
library builds successfully, I run into a problem when the newly built
python runs build_ext; it builds the _struct module and then
immediately afterwards my build environment throws an 'undefined
reference to dlopen' error.

To figure out what is missing dlopen, I need to somehow figure out
what build_ext is trying to do.  I've tried running the command
manually with the --verbose option with no results.

Does build_ext build modules in a certain order?  If so, what is that order?
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Re: recursive function: use a global or pass a parameter?

On Friday, January 16, 2015 at 11:26:46 PM UTC+5:30, Chris Angelico wrote:
 On Sat, Jan 17, 2015 at 4:49 AM, Tim  wrote:
  I want to get a union of all the values that any 'things' key may have, 
  even in a nested dictionary (and I do not know beforehand how deep the 
  nesting might go):
 
  d = {'things':1, 'two':{'things':2}}
 
  def walk(obj, res):
  if not hasattr(obj, 'keys'):
  return set(), set()
 
  if 'things' in obj:
  res.add(obj['things'])
 
  for k in obj:
  walk(obj[k], res)
 
  return res
 
  walk(d, set()) # returns {1, 2}
 
  Is it better to use a global to keep track of the values or does it even 
  matter?
 
 I would use a parameter rather than a global, but I'd make the
 parameter optional:
 
 def all_keys(obj, accum=None):
 if accum is None: accum=set()
 if 'things' in obj:
 res.add(obj['things'])
 for val in obj.values():
 all_keys(val, accum)
 return all_keys
 
 ChrisA

I dont like the hardwired this. However keeping that...

def all_keys(obj):
if   not isinstance(obj, type({})): return set()

return ((set([obj['things']]) if 'things' in obj else set())   |
   set(v for s in obj.values() for v in all_keys(s)))
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Re: recursive function: use a global or pass a parameter?

2015-01-16 Thread Peter Otten

Tim wrote:

 I have this type of situation and wonder if I should use a global variable
 outside the recursive function instead of passing the updated parameter
 through.
 
 I want to get a union of all the values that any 'things' key may have,
 even in a nested dictionary (and I do not know beforehand how deep the
 nesting might go):
 
 d = {'things':1, 'two':{'things':2}}
 
 def walk(obj, res):
 if not hasattr(obj, 'keys'):
 return set(), set()
 
 if 'things' in obj:
 res.add(obj['things'])
 
 for k in obj:
 walk(obj[k], res)
 
 return res
 
 walk(d, set()) # returns {1, 2}
 
 Is it better to use a global to keep track of the values or does it even
 matter?

Globals are generally bad as they make code non-reentrant; when two calls of 
the function run simultaneously the data will be messed up.

I recommend that you use a generator:

 def walk(obj):
... if not hasattr(obj, keys):
... return
... if things in obj:
... yield obj[things]
... for v in obj.values():
... yield from walk(v)
... 
 d = {'things':1, 'two':{'things':2}}
 set(walk(d))
{1, 2}

In Python before 3.3 you have to replace

yield from walk(v)

with a loop:

for t in walk(v):
yield t

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Re: recursive function: use a global or pass a parameter?

2015-01-16 Thread Tim

On Friday, January 16, 2015 at 1:34:51 PM UTC-5, Peter Otten wrote:
 Tim wrote:
 
 Globals are generally bad as they make code non-reentrant; when two calls of 
 the function run simultaneously the data will be messed up.
 
 I recommend that you use a generator:
 
  def walk(obj):
 ... if not hasattr(obj, keys):
 ... return
 ... if things in obj:
 ... yield obj[things]
 ... for v in obj.values():
 ... yield from walk(v)
 ... 
  d = {'things':1, 'two':{'things':2}}
  set(walk(d))
 {1, 2}
 
 In Python before 3.3 you have to replace
 
 yield from walk(v)
 
 with a loop:
 
 for t in walk(v):
 yield t

Ah, a generator, I wouldn't have seen the problem in this way, but with your 
example, it looks so natural.

thanks,
--Tim
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[ANN] Pylint 1.4.1 / Astroid 1.3.3 released

2015-01-16 Thread Claudiu Popa

Hello,

It's my pleasure to announce the release of both Pylint 1.4.1 and
Astroid 1.3.3 respectively.

The following bug fixes and features made their way into Astroid 1.3.3:

* Restore file_stream to a property, but deprecate it in favour of
the newly added method Module.stream.

* Add inference tips for 'tuple', 'list', 'dict' and 'set' builtins.

* Add brain definition for most string and unicode methods

* Add a new method to Class nodes, 'mro', for obtaining the
the method resolution order of the class.

* Add brain tips for six.moves. Closes issue #63.

* .slots() can contain unicode strings on Python 2.

* Add inference tips for nose.tools.

The complete list of changes can be seen here:
https://bitbucket.org/logilab/astroid/src/15cff6016b793bb64c92d04acc4da001a2c98683/ChangeLog?at=default#cl-4

For Pylint, we have the following fixes and features:

* Add a new JSON reporter, usable through -f flag.

* Add a new warning, 'redundant-unittest-assert', emitted when using
unittest's methods assertTrue and assertFalse with constant value
as argument.

* Check the return of properties when checking for not-callable.
Closes issue #406.

* Warn about using the input() or round() built-ins for Python 3.
Closes issue #411.

* Use a mro traversal for finding abstract methods. Closes issue #415.

* Fix a false positive on Python 2 for raising-bad-type, when
raising tuples in the form 'raise (ZeroDivisionError, None)'.

* Fix a false positive with invalid-slots-objects, where the slot entry
was an unicode string on Python 2. Closes issue #421.

The complete list of changes can be found here:
https://bitbucket.org/logilab/pylint/src/02eabae6b72569876e7104db7724ad26a7de0af3/ChangeLog?at=default#cl-4

If you find any bugs, don't hesitate to open a new issue on our issue
tracker (https://bitbucket.org/logilab/pylint/)

Enjoy!
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Re: lambdak: multi-line lambda implementation in native Python


Marko Rauhamaa wrote:

Gregory Ewing greg.ew...@canterbury.ac.nz:


If those are 24-bit RGB pixels, you could encode
3 characters in each pixel.


Not since Python3. Characters are Unicode now so you'll need to dedicate
a pixel for each character.


Depends on which characters you want. With the
Flexible Chromatic Representation, it could be
anything from 1 to 3.

--
Greg
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Re: Factories and Builders [was Re: lambdak...]


Steven D'Aprano wrote:

I've never really understand why abstract factory, factory method
and builder are considered different design patterns. They're variants on
the same idea.


I think it's because they address different problems. Factories
are for hiding the details of how an object is constructed.
Builders are for working around the fact that there are no
keyword arguments in your language.

Builders are sometimes also used for algorithmic reasons;
e.g. Java's StringBuilder exists to save you from O(n**2)
behaviour when creating a string from many small parts.

Factories of various kinds can be useful in Python;
builders, not so much.

--
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Re: lambdak: multi-line lambda implementation in native Python


Chris Angelico wrote:

Is this to get
around style guides that reject this kind of model:

x = Foo(
opt1=True,
opt2=True,
color=Yellow,
)


It's to get around the fact that you *can't* do that in
Java, because it doesn't have keyword arguments.

This is a source of a lot of the complexity and boilerplate
found in Java code -- the need to work around deficencies
in the language.


But if you can
pass a mapping object to the constructor, you can do the same job that
way,


Yes, but constructing the mapping object is just as
tedious. :-(


you could pass an array of
item,value,item,value,item,value or something.


That's certainly possible, but then you have to write
tedious code in the constructor to parse the arguments,
you lose compile-time type safety, incur runtime
overhead, etc.

We're really quite spoiled in Python-land. It's easy
to forget just *how* spoiled we are until you go back
and try to do something in one of the more primitive
languages...

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Re: recursive function: use a global or pass a parameter?


Tim wrote:

I have this type of situation and wonder if I should use a global variable
outside the recursive function instead of passing the updated parameter
through.


No! Globals are evil, at least for that sort of thing.
The way you're doing it is fine.

The only thing I would change is to wrap it all up
in a top-level function that takes care of creating
the result set and returning it.

def walk(obj):
  res = set()
  _walk(obj, res)
  return res

def _walk(obj, res):
  ...

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Re: recursive function: use a global or pass a parameter?

On Sat, Jan 17, 2015 at 9:20 AM, Gregory Ewing
greg.ew...@canterbury.ac.nz wrote:
 The only thing I would change is to wrap it all up
 in a top-level function that takes care of creating
 the result set and returning it.

 def walk(obj):
   res = set()
   _walk(obj, res)
   return res

 def _walk(obj, res):
   ...

Point of style: I like to put these kinds of helpers _above_ the
corresponding public functions, to maintain a general policy of
Define-Before-Use. Tends to make code easier to read; the first
reference to a function name is its definition, then all usage comes
after that. It's not always possible, of course (eg mutual recursion),
but in simple cases like this, it's easy enough.

ChrisA
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Re: recursive function: use a global or pass a parameter?

2015-01-16 Thread Yawar Amin

On Friday, January 16, 2015 at 1:34:51 PM UTC-5, Peter Otten wrote:
 [...]
 I recommend that you use a generator:
 
  def walk(obj):
 ... if not hasattr(obj, keys):
 ... return
 ... if things in obj:
 ... yield obj[things]
 ... for v in obj.values():
 ... yield from walk(v)

Cool ... but it looks like this can still potentially hit the max
recursion limit? Perhaps better to convert to an iterative style:

def walk(obj):
  
  Yield any value(s) contained within `obj` that is (are) indexed by
  the key 'things'. `obj` must be dict-like.
  
  from collections import deque
  vals = deque()
  vals.append(obj)

  while True:
try: curr_obj = vals.popleft()
except IndexError: return
if not hasattr(curr_obj, keys): continue

if things in curr_obj: yield curr_obj[things]
vals.extend(curr_obj.values())

# Examples

d1 = list(walk({ things: 1, two: { things: 2 } }))

d2 = list(walk({
  things: 1,
  two: { things: 2 },
  three:
{ four: 4,
  things:
{ five: 5,
  six: 6,
  things:
{ seven: 7,
  things: 8 } } } }))

So this effectively 'flattens' a dictionary at each level into a queue
made up of the dictionary's values, and meanwhile yields the values one
by one if they are indexed by the key 'things'.

The output for `d1` should be the same as Peter Otten's example, except
I'm using a list instead of a set because I think the yielded objects
could themselves be dictionaries or other non-hashable values.

When you're looking at the output for `d2`, remember that `walk` here
will yield _any_ object that's indexed by the key, and as I mentioned,
that could be an entire dictionary object contained within the main one.

Regards,

Yawar
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pyqtdeploy on windows

2015-01-16 Thread Hektor black


hi
i have a code with pyqt4 and i want run in android with this tutorial
http://pyqt.sourceforge.net/Docs/pyqtdeploy/command_line.html
my project include of : m.py m.pyw m.ui
when run pyqtdeploy myproject.pdy in cmd get error
installing py 3.4.2 pyqt5 for pyqtdeploy
any one know good tutorial for this module

tnx
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Re: recursive function: use a global or pass a parameter?

2015-01-16 Thread Yawar Amin

On Friday, January 16, 2015 at 9:24:15 PM UTC-5, Yawar Amin wrote:
 [...]
 vals.extend(curr_obj.values())

Ah, I should mention that the above will do a breadth-first search. If
we want to do a depth-first search we simply replace the above line
with:

vals.extendleft(curr_obj.values())

Regards,

Yawar
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EuroPython 2015: Your chance to sign up as a launch sponsor

2015-01-16 Thread M.-A. Lemburg

Companies who would like to sign up as a EuroPython 2015 launch sponsor
are encouraged to contact the sponsor work group at:

sponsor...@europython.eu

Launch sponsors will get the additional benefit of being listed on the
website when we launch - for free. You just need to be quick, since the
launch is planned for early in February.

More Booths and more Sponsor Slots
--

The Euskalduna Conference Center and Concert Hall (ECC) venue in Bilbao
was chosen as conference venue for EuroPython 2015:

http://www.euskalduna.net/Index.asp?idioma=en

It offers plenty of room for sponsor booths, so we will try to make
EuroPython 2015 as effective as possible for you as sponsors by offering
more booth space and sponsor slots than ever before:

http://www.euskalduna.net/espacios/espacios_hall_exposiciones.asp

This is your chance to reach out to more than a thousand enthusiastic
and highly motivated EuroPython attendees !

Please email us at sponsor...@europython.eu and we’ll send you the
sponsor brochure.

Thanks,
—
EuroPython Society (EPS)
http://www.europython-society.org/

PS: Please help spread the word and forward this email to companies
you know, your local lists, user groups, etc. Many thanks !
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xlwings v0.3.1 released

2015-01-16 Thread Felix Zumstein

I am happy to announce the release of xlwings v0.3.1: 

This fixes a long-standing bug that caused Excel to close/reopen under certain 
circumstances. It also adds a Workbook.set_mock_caller() method that makes it a 
lot easier to call code from Excel and Python without changes.

See the full Release Notes here: 
http://docs.xlwings.org/whatsnew.html 

About xlwings: 
xlwings is a BSD-licensed python library that makes it easy to call python from 
Excel and vice versa: 

Interact with Excel from python using a syntax that is close to VBA yet 
pythonic. 
Replace your VBA macros with python code and still pass around your workbooks 
as easily as before. 
xlwings fully supports NumPy arrays and Pandas DataFrames. 

It works with Microsoft Excel on Windows and Mac. 

http://xlwings.org 
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[issue23248] Update ssl data


New submission from Antoine Pitrou:

Amusingly OpenSSL has removed some error codes, so perhaps we should only apply 
this to the default branch.

--
components: Library (Lib)
files: update_ssl_data.patch
keywords: patch
messages: 234114
nosy: alex, christian.heimes, dstufft, giampaolo.rodola, janssen, pitrou
priority: normal
severity: normal
stage: patch review
status: open
title: Update ssl data
type: behavior
versions: Python 3.5
Added file: http://bugs.python.org/file37722/update_ssl_data.patch

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[issue15955] gzip, bz2, lzma: add option to limit output size


Antoine Pitrou added the comment:

I've posted a review of the latest lzma decompressor patch. I think it'll be 
able to go in once the comments are addressed.

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[issue23051] multiprocessing.pool methods imap()[_unordered()] deadlock


Antoine Pitrou added the comment:

The patch would at least need to add a unit test in order to avoid regressions.

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[issue14953] Reimplement subset of multiprocessing.sharedctypes using memoryview


Changes by Antoine Pitrou pit...@free.fr:


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[issue21354] PyCFunction_New no longer exposed by python DLL breaking bdist_wininst installers


Changes by Antoine Pitrou pit...@free.fr:


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[issue1103213] Adding the missing socket.recvall() method


Antoine Pitrou added the comment:

I'm frankly not sure why this is useful. If you want a guaranteed read size you 
should use the buffered layer - i.e. socket.makefile(). No need to complicate 
the raw socket implementation.

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[issue20544] Use specific asserts in operator tests


Changes by Antoine Pitrou pit...@free.fr:


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[issue23133] Pickling of ipaddress classes