Re: Python programming

[Larry Hudson]

I spotted a device on the table of the company calibration office...

As I recall, it was a 100A capable resistor... 0.10 OHM.

No idea what it was meant for; big binding posts at one end, and a slab
of sheet steel in a "W" shape (smooth curves, not sharp bends).


External shunt for an ammeter?



More likely a dummy load for power supply testing.  (Normally, ammeter shunts 
are sized to dissipate as little power as possible.)

-Bill



Another (OT) story...

I used to work in an electronic calibration lab, but I don't recall having a resistor of that 
description -- however, it reminds me of another story...


While our job was calibrating and maintaining our company's electronics, we occasionally had to 
do some incoming inspection work -- checking incoming components for accuracy.  This particular 
time I had a batch of 0.1 ohm 1% resistors (I think those were the numbers, at least something 
on that order).  I found by checking them right at the body of the resistors they were 
out-of-spec low, and checking at the end of the leads they were out-of-spec high.  Fun!   :-)


To measure them, I used the lab's Current Calibrator -- a special power supply whose voltage was 
controlled to give a constant (dialed-in) current.  Then with a DVM and mini-hooks I could 
attach these DVM leads anyplace along the resistor's leads.  At 1 amp, the voltage (read on the 
DVM) was equal to the resistance.  Ohm's law, of course:  R = E/I, where I is a constant 1.  And 
1 amp was well within the power specs of these resistors.


I ended up checking them at a distance of about a quarter inch from the body, because I expected 
that would be about the way they would be eventually mounted.  They all passed that way.  And 
fortunately I never had another batch of these resistors!   :-)


 -=- Larry -=-

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Re: why does "python --version" write to standard error?

[Ned Deily]

In article <20140307075744.ga43...@cskk.homeip.net>,
 Cameron Simpson  wrote:

> This seems to write the python version to standard error. That seems
> very wrong. And at variance with the manual entry.

Fixed in Python 3.4:
http://bugs.python.org/issue18338

-- 
 Ned Deily,
 n...@acm.org

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problem running python 3.3 on mac os mavericks

[Romil Agrawal]

I currently installed python 3.3.4 on mac os mavericks, and want to run it
on Wing IDE. Previously it was running python 2.7.6. When I tried to change
the python excitable in the wing ide configuration mode, and then restarted
it, a dialog box was displayed that said the interpreter of python 3.3.4 on
the specified path may not exist. Please help me sort this out. Also,
python 3.3.4 is installed on my mac and running on the IDLE, but the
terminal shows that the current version of python is 2.7.6. how can it be
possible. Please suggest something to sort this thing out.

Thanking you.
Regards,
Romil Agrawal
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Re: Tuples and immutability

[Duncan Booth]

Chris Angelico  wrote:

> On Sat, Mar 1, 2014 at 1:41 AM, Joshua Landau 
> wrote: 
>> Would it be better to add a check here, such that if this gets raised
>> to the top-level it includes a warning ("Addition was inplace;
>> variable probably mutated despite assignment failure")?
> 
> That'd require figuring out whether or not the variable was actually
> mutated, and that's pretty hard to work out. So there's a FAQ entry,
> which Zachary already posted:
> 
> http://docs.python.org/3/faq/programming.html#why-does-a-tuple-i-item-r
> aise-an-exception-when-the-addition-works 
> 
> Also, we just answer this question every now and then :) Presumably
> more often on -tutor than here.
> 
> ChrisA
Another take on this that I haven't seen discussed in this thread:

Is there any reason why tuples need to throw an exception on assigning to 
the element if the old value and new value are the same object?

If I say:

a = ("spam", [10, 30], "eggs")

then

a[0] = a[0]

won't actually mutate the object. So tuples could let that silently pass. 
Then you would be able to safely do:

a[1] += [50]

but this would still throw an exception:

a[0] += "x"



-- 
Duncan Booth http://kupuguy.blogspot.com
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Re: why does "python --version" write to standard error?

[Cameron Simpson]

On 07Mar2014 00:31, Ned Deily  wrote:
> In article <20140307075744.ga43...@cskk.homeip.net>,
>  Cameron Simpson  wrote:
> > This seems to write the python version to standard error. That seems
> > very wrong. And at variance with the manual entry.
> 
> Fixed in Python 3.4:
> http://bugs.python.org/issue18338

Excellent! My thanks to Berker Peksag and Michael Dickens and the
other ticket participants.
-- 
Cameron Simpson 

The double cam chain setup on the 1980's DOHC CB750 was another one of
Honda's pointless engineering breakthroughs. You know the cycle (if you'll
pardon the pun :-), Wonderful New Feature is introduced with much fanfare,
WNF is fawned over by the press, WNF is copied by the other three Japanese
makers (this step is sometimes optional), and finally, WNF is quietly dropped
by Honda.
- Blaine Gardner, 
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Re: gdb unable to read python frame information

[Wesley]

Then, how to make python get debug symbols? 

Install python from source with some special configure options?
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Re: Tuples and immutability

[Ben Finney]

Duncan Booth  writes:

> Is there any reason why tuples need to throw an exception on assigning
> to the element if the old value and new value are the same object?

Special cases aren't special enough to break the rules.

-- 
 \   “I do not believe in forgiveness as it is preached by the |
  `\church. We do not need the forgiveness of God, but of each |
_o__)other and of ourselves.” —Robert G. Ingersoll |
Ben Finney

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Re: Tuples and immutability

[Chris Angelico]

On Fri, Mar 7, 2014 at 8:33 PM, Duncan Booth
 wrote:
> Is there any reason why tuples need to throw an exception on assigning to
> the element if the old value and new value are the same object?

It'd be easy enough to implement your own tuple subclass that behaves
that way. Try it! See how many situations it actually helps.

ChrisA
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Re: Assertions are bad, m'kay?

[Steven D'Aprano]

On Fri, 07 Mar 2014 18:16:55 +1100, Chris Angelico wrote:

> They produce the wrong exception type, they disappear when you least
> expect them, and now we have another reason not to use assert.
> 
> http://xkcd.com/1339/
> 
> Abusing assert for arg checking violates XKCD 1339. Write
> standards-compliant code!

Assertions are not bad! They're just misunderstood and abused.

(By the way, assertions are not the same as assumptions. Asserts can be 
used to check that assumptions are correct, or to check the internal 
logic of your reasoning. Whereas assumptions are just accepted as if they 
were correct, no questions asked.


You should read this guy's blog post on when to use assert:

http://import-that.dreamwidth.org/676.html

It's pretty damn good, if I do say so myself...

*whistles innocently*


-- 
Steven D'Aprano
http://import-that.dreamwidth.org/
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Re: Assertions are bad, m'kay?

[Chris Angelico]

On Fri, Mar 7, 2014 at 10:11 PM, Steven D'Aprano
 wrote:
>> http://xkcd.com/1339/
>>
>> Abusing assert for arg checking violates XKCD 1339. Write
>> standards-compliant code!
>
> Assertions are not bad! They're just misunderstood and abused.
>
> (By the way, assertions are not the same as assumptions. Asserts can be
> used to check that assumptions are correct, or to check the internal
> logic of your reasoning. Whereas assumptions are just accepted as if they
> were correct, no questions asked.

The XKCD does draw a distinction between assuming and asserting. And I
do say "for arg checking", which is the most common *abuse* of assert.
But mainly, I just like to share laughs :)

ChrisA
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Re: Tuples and immutability

[Peter Otten]

Chris Angelico wrote:

> On Fri, Mar 7, 2014 at 8:33 PM, Duncan Booth
>  wrote:
>> Is there any reason why tuples need to throw an exception on assigning to
>> the element if the old value and new value are the same object?
> 
> It'd be easy enough to implement your own tuple subclass that behaves
> that way. Try it! See how many situations it actually helps.

>>> class T(tuple):
... def __setitem__(self, index, value):
... if value is not self[index]:
... raise TypeError("{} is not {}".format(value, 
self[index]))
... 
>>> for i, k in zip(range(250, 260), range(250, 260)):
... T([i])[0] = k
... 
Traceback (most recent call last):
  File "", line 2, in 
  File "", line 4, in __setitem__
TypeError: 257 is not 257

I'm not sure "help" is the right word here ;)

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Re: Tuples and immutability

[Chris Angelico]

On Fri, Mar 7, 2014 at 10:38 PM, Peter Otten <__pete...@web.de> wrote:
> TypeError: 257 is not 257
>
> I'm not sure "help" is the right word here ;)

It doesn't help with non-small integers, yes, but the original case
was a list. Personally, I don't think there are many situations that
would benefit from it, plus it'd be confusing ("I can use += with a
list but not a number, why not?!").

ChrisA
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Re: Tuples and immutability

[Alister]

On Fri, 07 Mar 2014 09:33:49 +, Duncan Booth wrote:

> Chris Angelico  wrote:
> 
>> On Sat, Mar 1, 2014 at 1:41 AM, Joshua Landau  wrote:
>>> Would it be better to add a check here, such that if this gets raised
>>> to the top-level it includes a warning ("Addition was inplace;
>>> variable probably mutated despite assignment failure")?
>> 
>> That'd require figuring out whether or not the variable was actually
>> mutated, and that's pretty hard to work out. So there's a FAQ entry,
>> which Zachary already posted:
>> 
>> http://docs.python.org/3/faq/programming.html#why-does-a-tuple-i-item-r
>> aise-an-exception-when-the-addition-works
>> 
>> Also, we just answer this question every now and then :) Presumably
>> more often on -tutor than here.
>> 
>> ChrisA
> Another take on this that I haven't seen discussed in this thread:
> 
> Is there any reason why tuples need to throw an exception on assigning
> to the element if the old value and new value are the same object?
> 
> If I say:
> 
> a = ("spam", [10, 30], "eggs")
> 
> then
> 
> a[0] = a[0]
> 
> won't actually mutate the object. So tuples could let that silently
> pass.
> Then you would be able to safely do:
> 
> a[1] += [50]
> 
> but this would still throw an exception:
> 
> a[0] += "x"

I would think it would be better if the exception was thrown before the 
assignment to the list took place
simply seeing that a modification action was being applied to a tupple 
should be enough.
this would alert the programmer to the fact that he was trying something 
that may have undesired consequences
 



-- 
Old age is the harbor of all ills.
-- Bion
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GOLLY! HUMANS HAVE ORIGINS IN THE DEVONIAN!

[thrinaxodon . of . use . net123]

==
>HOLY F*CKING GOD DAMNED NEWS!
==
>
WELCOME TO YOUR NUMBER ONE SOURCE FOR PRESTIGIOUS BULLLSHIT! THE KIND YOU CAN 
ONLY GET FROM THRINAXODON CRAZY CHEESY!
>
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>
==
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>
ONE OF THEM WAS A NICE KNEECAP.
>
THE MOST BEAUTIFUL KNEECAP EVER DISCOVERED.
>
I CALLED OUT CARTER N.
>
CARTER CAME RUSHING OVER. WE TOOK THE KNEECAP FROM THE INUIT SAVAGES AND FLEW 
TO THE SMITHSONIAN.
>
THEY CALLED US KOOKS AND SLAMMED THE DOOR.
>
==
EVIDENCE THAT HUMANS LIVED IN THE DEVONIAN: 

https://groups.google.com/group/sci.bio.paleontology/browse_thread/thread/6f501c469c7af24f#
 
https://groups.google.com/group/sci.bio.paleontology/browse_thread/thread/3aad75c16afb0b82#
 
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Re: gdb unable to read python frame information

[Neal Becker]

dieter wrote:

> Wesley  writes:
> 
>> I wanna use gdb to attach my running python scripts.
>> Successfully import libpython in gdb, but seems all py operations failed to
>> read python information.
>>
>> Here is the snippet:
>> (gdb) python
>>>import libpython
>>>end
>> (gdb) py-bt
>> #3 (unable to read python frame information)
>> #5 (unable to read python frame information)
> 
> The simplest possible interpretation would be that your
> Python lacks debugging symbols. That often happens with
> system installed Python installations (which usually are stripped
> to the bare minimal symbol set - as "normal" users do not need
> debugging).
> 
> Try with a Python that you have generated yourself.

You probably need to install the python-debuginfo package

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debugging on windows

[Robin Becker]

Using


Python 3.3.3 (v3.3.3:c3896275c0f6, Nov 18 2013, 21:18:40) [MSC v.1600 32 bit 
(Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.


to run a tkinter + pmw2 application I have the following error on windows xp sp3


Unhandled exception at 0x1e0aebb8 in python.exe: 0xC005: Access violation 
reading location 0x0048.


the main window has appeared and the app is in a module search to find 
files/classes that might be relevant. VS 2010 indicates the error is some where 
 in the python33 dll. The code appears to run fine in 2.7, but should be 
compatible with 3.3.x


Is my only hope to add more print statements or use pdb or should I try and 
compile python 3.3.x myself and get the search narrowed with VS? The issue is 
complicated by my having redirected all outputs to some message windows using 
fake files for stderr & stdout.



--
Robin Becker

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Re: Tuples and immutability

[Roy Smith]

In article ,
 Duncan Booth  wrote:

> Is there any reason why tuples need to throw an exception on assigning to 
> the element if the old value and new value are the same object?
> 
> If I say:
> 
> a = ("spam", [10, 30], "eggs")
> 
> then
> 
> a[0] = a[0]
> 
> won't actually mutate the object. So tuples could let that silently pass. 

But, why would you want them to?  What a way to introduce bugs which are 
difficult to test for.
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Re: Python programming

[Grant Edwards]

On 2014-03-07, William Ray Wing  wrote:
> On Mar 6, 2014, at 8:24 PM, Roy Smith  wrote:

>>> I spotted a device on the table of the company calibration office...
>>> 
>>> As I recall, it was a 100A capable resistor... 0.10 OHM.
>>> 
>>> No idea what it was meant for; big binding posts at one end, and a
>>> slab of sheet steel in a "W" shape (smooth curves, not sharp bends).
>> 
>> External shunt for an ammeter?
>>  
>
> More likely a dummy load for power supply testing.

Could be.  Back when I was working on PWM controllers for golf cart
and small car motors, we used to use steel coathangers for test loads,
but once they got past orange and more towards yellow, they started to
get too soft.  An appropriately dimensioned chunk of sheet steel would
have been ideal.

> (Normally, ammeter shunts are sized to dissipate as little power as
> possible.)

I've used chunks of coathanger for that too, but I don't think the
resistance was stable enough over temperature to trust the results at
higher currents.

-- 
Grant Edwards   grant.b.edwardsYow! If elected, Zippy
  at   pledges to each and every
  gmail.comAmerican a 55-year-old
   houseboy ...
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Re: Python programming

[John Ladasky]

On Thursday, February 13, 2014 12:30:39 AM UTC-8, larry@gmail.com wrote:
> On Wed, Feb 12, 2014 at 10:56 PM, William Ray Wing  wrote:
> 
> > OK, and how many of you remember the original version of the 
> > tongue-in-cheek essay "Real Programmers Don't Use Pascal" from the back 
> > page of Datamation?
> 
> I do remember it.
> 
> http://www.webcitation.org/659yh1oSh


As do I, though I couldn't have been more than about 16 years old when it came 
out.  I just re-read it, and this comment jumped out at me:

"Neither OS/370 nor FORTRAN show any signs of dying out, despite all the 
efforts of Pascal programmers the world over."

Well, OS/370, RIP.

As for FORTRAN?  This week, I actually downloaded an application which required 
a FORTRAN compiler.  This is the only FORTRAN application I've ever needed.  
It's not old code, the first revision came out about 10 years ago.  More than 
once, I have queried Google with the phrase "Why isn't FORTRAN dead yet?"  For 
some reason, it lives on.  I can't say that I understand why.  
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Is their a command to view code?

[NexusRAwesome1995 .]

I am making a text based aventure game for my assignment and a friends test
run has somehow saved over the entire code file and now im using an earlier
version of the code. I have 0 idea if there is anyway to look at the code
using the IDLE and i need to do it to see how i fixed the fatal error left
behind by a friend. My on computer backup has not worked and the backup on
my memory stick also has the same problem.
If anyone knows of a way to get my code back i will be grateful as this is
my 1st project and i'm not that used to the syntax.
the item added is the outcome of what happened.
Python 2.7.3 (default, Apr 10 2012, 23:31:26) [MSC v.1500 32 bit (Intel)] on 
win32
Type "copyright", "credits" or "license()" for more information.
 RESTART 
>>> 
REMEMBER TO TYPE ALL YOUR ANSWERS IN LOWERCASE (EXCEPT YOUR OWN NAME)
>>> 
>>>  RESTART 
>>> 
REMEMBER TO TYPE ALL YOUR ANSWERS IN LOWERCASE (EXCEPT YOUR OWN NAME)
BECAUSE THIS IS OUR FIRST GAME, ANY ANSWERS NOT ENTERED PERFECTLY WILL RESULT 
IN THE GAME ENDING, SO BE CAREFUL!
Hello, please enter your name:
Marcus Hyde
Marcus Hyde, You begin your adventure in the forest, with Princess Violet.
You proceed to climb a tree to pick an apple when you hear her scream.
A group of Orcs have taken the princess!
What will you do?
 Attack
 Run
attack
You try to attack one of the Orcs but they are too strong!
You are knocked out!
...
You awaken moments later to see a spirit in front of you.
The spirit presents you with three choices, select one.
 Sword
 Staff
 Bow
staff
You chose Staff!
('Staff does ', 4, ' damage!')
You are now equiped with a weapon!
Weapons increase your attack power, making you capable of defeating stronger 
opponents!
When you are given a choice, you can check your stats by typing 'stats'
Give it a try!
What will you do?
 Stats
stats
('HP = ', 10)
('Attack = ', 4)
('Defense = ', 0)
As you advance through the game, you may find items to increase your stats.
...
Before you can move, you are attacked by a Rogue!
Rogue HP = 3
What will you do?
 Attack
 Run
attack
('You attack the Rogue and deal ', 4, ' damage.')
You defeated the Rogue!
Rogue droped an item!
What will you do?
 Check
 Leave
check
You found a Wooden Shield!
Defense = 1
What will you do?
 Stats
 Continue
continue
You continue in search of the Princess and find a cave.
There is a lit torch at the entrance of the cave.
You take the torch and proceed to enter the cave.
As you walk through the cave you notice strange symbols on the walls, what 
could they mean?
You continue walking and come across two paths.
You hear the sound of several Orcs coming from the Left path.
You feel the wind coming from the Right path, this way is the fastest to the 
exit.
What will you do?
 Left
 Right
left
Despite hearing several Orcs, you choose to take the left path.
You fall into a pit with 5 Orcs, one of them attacks you!
Orc HP = 6
What will you do?
 Attack
 Run
run
You try to run away but the Orcs grab you.
The Orcs beat you to death.
GAME OVER
>>> fuck

Traceback (most recent call last):
  File "", line 1, in 
fuck
NameError: name 'fuck' is not defined
>>> 
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Re: Tuples and immutability

[Ian Kelly]

On Fri, Mar 7, 2014 at 4:51 AM, Alister  wrote:
> I would think it would be better if the exception was thrown before the
> assignment to the list took place
> simply seeing that a modification action was being applied to a tupple
> should be enough.
> this would alert the programmer to the fact that he was trying something
> that may have undesired consequences

Then the behavior of tuples would be inconsistent with other immutable
types.  This can't be applied generally, because the Python
interpreter doesn't generally know whether a given type is supposed to
be immutable or not.
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Re: Python programming

[Gene Heskett]

On Friday 07 March 2014 12:29:38 Grant Edwards did opine:

> On 2014-03-07, William Ray Wing  wrote:
> > On Mar 6, 2014, at 8:24 PM, Roy Smith  wrote:
> >>> I spotted a device on the table of the company calibration office...
> >>> 
> >>> As I recall, it was a 100A capable resistor... 0.10 OHM.
> >>> 
> >>> No idea what it was meant for; big binding posts at one end, and a
> >>> slab of sheet steel in a "W" shape (smooth curves, not sharp bends).
> >> 
> >> External shunt for an ammeter?
> > 
> > More likely a dummy load for power supply testing.
> 
> Could be.  Back when I was working on PWM controllers for golf cart
> and small car motors, we used to use steel coathangers for test loads,
> but once they got past orange and more towards yellow, they started to
> get too soft.  An appropriately dimensioned chunk of sheet steel would
> have been ideal.
> 
> > (Normally, ammeter shunts are sized to dissipate as little power as
> > possible.)
> 
> I've used chunks of coathanger for that too, but I don't think the
> resistance was stable enough over temperature to trust the results at
> higher currents.

This is really really offtopic but since its turned into war stories,
I recall one time that I needed to test a 5v 200amp supply that there were 
2 of in an old NEC Digital Video Effects unit,  I looked up the R per 1000' 
of standard romex in the various gauges & went over the Lowes and bought a 
100' roll of of 10/2.  Soldered the inside end together after striping and 
twisting it together,  It worked well, but the PSU didn't.  Made by HP back 
when they _thought_ they knew about how to build cement block sized power 
supplies. The psu went into foldback at about 20 amps.  All the bugs were 
good, nothing running warm.  Analyzing backwards in view of the curie point 
on some ferrite's being below the boiling point of water, I finally came to 
the conclusion that the ferrite in the output transformer had gone 
austenitic, eg totally non-magnetic, like it was just so much air, which is 
what many of those compounds will do if magnetized near saturation when 
they hit the curie point, and will never recover from.  HP of course didn't 
have the transformer or a replacement supply, but I found some Pioneer's 
with a suitable rating at M.P.Jones in FL and broke their hands putting a 
check for 2 of them in them, shipped yesterday.  That was in about 1997 & 
they were still in service when we turned analog tv off June 30, 2008. 

Cheers, Gene
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

NOTICE: Will pay 100 USD for an HP-4815A defective but
complete probe assembly.

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Re: Is their a command to view code?

[Ian Kelly]

On Fri, Mar 7, 2014 at 10:55 AM, NexusRAwesome1995 .
 wrote:
> I am making a text based aventure game for my assignment and a friends test
> run has somehow saved over the entire code file and now im using an earlier
> version of the code. I have 0 idea if there is anyway to look at the code
> using the IDLE and i need to do it to see how i fixed the fatal error left
> behind by a friend. My on computer backup has not worked and the backup on
> my memory stick also has the same problem.
> If anyone knows of a way to get my code back i will be grateful as this is
> my 1st project and i'm not that used to the syntax.
> the item added is the outcome of what happened.

Sorry, Python doesn't keep the source code in memory.  If the game is
still running in the interpreter, you can ask it for the source code
of a particular code object, but it implements this by opening the
source file and reading it in.  Since you've overwritten the file, the
source code would be wrong.  The best that you could do in this case
would be to disassemble the code objects using the dis.dis() function,
and then try to reverse-engineer the Python code from the byte code.
If the interpreter is no longer running, then there is nothing you can
do.

For the future, I strongly recommend using a version control system,
such as the free and relatively lightweight Mercurial.  Then when you
have these kinds of mishaps all you have to do is check the most
recent version of the code out of the repository again.  You should of
course continue to create backups as well, in case of more disastrous
events (although memory sticks are far too failure-prone to be
considered a reliable backup solution IMO).
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Re: Is their a command to view code?

[Joel Goldstick]

On Mar 7, 2014 1:16 PM, "NexusRAwesome1995 ." 
wrote:
>
> I am making a text based aventure game for my assignment and a friends
test run has somehow saved over the entire code file and now im using an
earlier version of the code. I have 0 idea if there is anyway to look at
the code using the IDLE and i need to do it to see how i fixed the fatal
error left behind by a friend. My on computer backup has not worked and the
backup on my memory stick also has the same problem.
> If anyone knows of a way to get my code back i will be grateful as this
is my 1st project and i'm not that used to the syntax.
> the item added is the outcome of what happened.
>
You will be better off asking on python tutor list. However, go back to the
source you have and debug it
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>
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extract from json

[teddybubu]

I can't find any example on how to do this.
I have a json file like so:
{"bostock":[{"url":"http://bl.ocks.org/mbostock/9360565","title":"titleplaceholder","date":"dateplaceholder"},
{"url":"http://bl.ocks.org/mbostock/9265674","title":"titleplaceholder","date":"dateplaceholder"},
{"url":"http://bl.ocks.org/mbostock/9265467","title":"titleplaceholder","date":"dateplaceholder"},
{"url":"http://bl.ocks.org/mbostock/9234731","title":"titleplaceholder","date":"dateplaceholder"},
{"url":"http://bl.ocks.org/mbostock/9232962","title":"titleplaceholder","date":"dateplaceholder"},

this goes on for more than 700 entries. only thing unique is the number at the 
end of the url. I am going to load the url in python, get the date and title 
and write it in the json itself. 
Right now I am stuck on just reading the url in the json. Here is my code:

import json

with open("bostock.json") as json_file:
json_data = json.load(json_file)
print(json_data)

I have tried json_data[0], json_data.url and a few others I forget right now 
and it does not seem to work.  

I have already figured out how to get the title and date.
First things first: How can i just get the url for each line of the above json 
file? 
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Re: gdb unable to read python frame information

[Ned Deily]

In article ,
 Wesley  wrote:
> Then, how to make python get debug symbols? 
> 
> Install python from source with some special configure options?

If your distribution doesn't have a debug version of Python and you need 
to build your own, add --with-pydebug to your ./configure options.  See:

./configure --help

-- 
 Ned Deily,
 n...@acm.org

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Re: extract from json

[Kev Dwyer]

teddyb...@gmail.com wrote:

> I can't find any example on how to do this.
> I have a json file like so:
> {"bostock":
[{"url":"http://bl.ocks.org/mbostock/9360565","title":"titleplaceholder","date":"dateplaceholder"},
> 
{"url":"http://bl.ocks.org/mbostock/9265674","title":"titleplaceholder","date":"dateplaceholder"},
> 
{"url":"http://bl.ocks.org/mbostock/9265467","title":"titleplaceholder","date":"dateplaceholder"},
> 
{"url":"http://bl.ocks.org/mbostock/9234731","title":"titleplaceholder","date":"dateplaceholder"},
> 
{"url":"http://bl.ocks.org/mbostock/9232962","title":"titleplaceholder","date":"dateplaceholder"},
> 
> this goes on for more than 700 entries. only thing unique is the number at
> the end of the url. I am going to load the url in python, get the date and
> title and write it in the json itself. Right now I am stuck on just
> reading the url in the json. Here is my code:
> 
> import json
> 
> with open("bostock.json") as json_file:
> json_data = json.load(json_file)
> print(json_data)
> 
> I have tried json_data[0], json_data.url and a few others I forget right
> now and it does not seem to work.
> 
> I have already figured out how to get the title and date.
> First things first: How can i just get the url for each line of the above
> json file?


Hello 

Try:

Python 2.7.2 (default, Aug 19 2011, 20:41:43) [GCC] on linux2   

Type "help", "copyright", "credits" or "license" for more information.  


>>> import  json
>>> with open('/tmp/bostock.json') as f:
... json_data = json.load(f)
... 
>>> json_data
{u'bostock': [{u'url': u'http://bl.ocks.org/mbostock/9360565', u'date': 
u'dateplaceholder', u'title': u'titleplaceholder'}, {u'url': 
u'http://bl.ocks.org/mbostock/9265674', u'date': u'dateplaceholder', 
u'title': u'titleplaceholder'}, {u'url': 
u'http://bl.ocks.org/mbostock/9265467', u'date': u'dateplaceholder', 
u'title': u'titleplaceholder'}, {u'url': 
u'http://bl.ocks.org/mbostock/9234731', u'date': u'dateplaceholder', 
u'title': u'titleplaceholder'}, {u'url': 
u'http://bl.ocks.org/mbostock/9232962', u'date': u'dateplaceholder', 
u'title': u'titleplaceholder'}]}

>>> urls = [x['url'] for x in json_data['bostock']]
>>> urls
[u'http://bl.ocks.org/mbostock/9360565', 
u'http://bl.ocks.org/mbostock/9265674', 
u'http://bl.ocks.org/mbostock/9265467', 
u'http://bl.ocks.org/mbostock/9234731', 
u'http://bl.ocks.org/mbostock/9232962']

Python loads the json in the file into a dictionary.  In this case, the 
dictionary has a single key, 'bostock', and the value in the dictionary for 
that key is a list (of dictionaries).  

To get the urls, you need to get the list 

json_data['bostock']

 and then iterate over it's elements, getting the value for the key url for 
each one.  
This is what the list comprehension 

[x['url'] for x in json_data['bostock']]

does.

I hope that helps,

Kev


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Re: Assertions are bad, m'kay?

[Dan Stromberg]

On Fri, Mar 7, 2014 at 3:11 AM, Steven D'Aprano
 wrote:

>
> Assertions are not bad! They're just misunderstood and abused.

> You should read this guy's blog post on when to use assert:
>
> http://import-that.dreamwidth.org/676.html

Nice article.

BTW, what about:

if value >= 3:
   raise AssertionError('value must be >= 3')

?
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Re: Assertions are bad, m'kay?

[Ben Finney]

Dan Stromberg  writes:

> BTW, what about:
>
> if value >= 3:
>raise AssertionError('value must be >= 3')

That would be very confusing, since it would only appear when the value
is >= 3. Were you making some other point?

-- 
 \“If this is your first visit to the USSR, you are welcome to |
  `\  it.” —hotel room, Moscow |
_o__)  |
Ben Finney

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Re: Assertions are bad, m'kay?

[Irmen de Jong]

On 8-3-2014 1:15, Dan Stromberg wrote:
> On Fri, Mar 7, 2014 at 3:11 AM, Steven D'Aprano
>  wrote:
> 
>>
>> Assertions are not bad! They're just misunderstood and abused.
> 
>> You should read this guy's blog post on when to use assert:
>>
>> http://import-that.dreamwidth.org/676.html
> 
> Nice article.
> 
> BTW, what about:
> 
> if value >= 3:
>raise AssertionError('value must be >= 3')
> 
> ?

I don't think this qualifies as an assertion. Also, because AssertionError is 
documented
as "Raised when an assert statement fails", I would never use it myself 
explicitly like
this.

You should use ValueError instead (or a more precise exception such as 
IndexError, if
appropriate).

Irmen




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Re: Function and turtle help

[Lee Harr]

> I am completely new to programming so thanks for any help!

Not sure it will help, and hopefully I am not self-promoting too much,
but this may be of interest to you:

http://pynguin.googlecode.com/

http://code.google.com/p/pynguin/wiki/StartProgramming


I am interested in feedback from new programmers.   
  
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Re: Function and turtle help

[Scott W Dunning]

On Mar 7, 2014, at 6:16 PM, Lee Harr  wrote:

>> I am completely new to programming so thanks for any help!
> 
> Not sure it will help, and hopefully I am not self-promoting too much,
> but this may be of interest to you:
> 
> http://pynguin.googlecode.com/
> 
> http://code.google.com/p/pynguin/wiki/StartProgramming
> 
Awesome!  Looks fun, I’ll definitely check it out and let you know!!

Scott
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Re: Tuples and immutability

[Gregory Ewing]

Duncan Booth wrote:
Is there any reason why tuples need to throw an exception on assigning to 
the element if the old value and new value are the same object?


It would make introspection misleading, because tuples
would have a __setitem__ method event though they don't
actually support item assignment.

Also, it would solve the problem for tuples in particular,
but not for any other immutable type -- they would all
have to implement the same behaviour independently to
enjoy the benefit.

Here's another idea: If the __iadd__ method returns the
same object, *and* the LHS doesn't have a __setitem__
method, then do nothing instead of raising an exception.

Peter Otten wrote:

> Traceback (most recent call last):
>   File "", line 2, in 
>   File "", line 4, in __setitem__
> TypeError: 257 is not 257
>
> I'm not sure "help" is the right word here ;)

I don't think that's a problem, because the use case
being addressed is where the object performs in-place
modification and always returns itself. Any object that
doesn't return itself is not modifying in-place, even
if the returned object happens to be equal to the
original one.

--
Greg
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Re: extract from json

[teddybubu]

On Friday, March 7, 2014 3:05:15 PM UTC-6, Kev Dwyer wrote:
>  wrote:
> > I can't find any example on how to do this.
> 
> > I have a json file like so:
> 
> > {"bostock":[{"url":"http://bl.ocks.org/mbostock/9360565","title":"titleplaceholder","date":"dateplaceholder"},{"url":"http://bl.ocks.org/mbostock/9265674","title":"titleplaceholder","date":"dateplaceholder"},{"url":"http://bl.ocks.org/mbostock/9265467","title":"titleplaceholder","date":"dateplaceholder"},{"url":"http://bl.ocks.org/mbostock/9234731","title":"titleplaceholder","date":"dateplaceholder"},{"url":"http://bl.ocks.org/mbostock/9232962","title":"titleplaceholder","date":"dateplaceholder"},
> > this goes on for more than 700 entries. only thing unique is the number at
> 
> > the end of the url. I am going to load the url in python, get the date and
> 
> > title and write it in the json itself. Right now I am stuck on just
> 
> > reading the url in the json. Here is my code:
> > import json
> > with open("bostock.json") as json_file:
> 
> > json_data = json.load(json_file)
> 
> > print(json_data)
> > I have tried json_data[0], json_data.url and a few others I forget right
> 
> > now and it does not seem to work.
> > I have already figured out how to get the title and date.
> 
> > First things first: How can i just get the url for each line of the above
> 
> > json file?
> Hello 
> Try:
> 
> Python 2.7.2 (default, Aug 19 2011, 20:41:43) [GCC] on linux2 
>   
> 
> Type "help", "copyright", "credits" or "license" for more information.
>   

> >>> import  json
> 
> >>> with open('/tmp/bostock.json') as f:
> 
> ... json_data = json.load(f)
> >>> json_data
> {u'bostock': [{u'url': u'http://bl.ocks.org/mbostock/9360565', u'date': 
> u'dateplaceholder', u'title': u'titleplaceholder'}, {u'url': 
> u'http://bl.ocks.org/mbostock/9265674', u'date': u'dateplaceholder', 
> u'title': u'titleplaceholder'}, {u'url': 
> u'http://bl.ocks.org/mbostock/9265467', u'date': u'dateplaceholder', 
> 
> u'title': u'titleplaceholder'}, {u'url': 
> 
> u'http://bl.ocks.org/mbostock/9234731', u'date': u'dateplaceholder', 
> u'title': u'titleplaceholder'}, {u'url': 
> u'http://bl.ocks.org/mbostock/9232962', u'date': u'dateplaceholder', 
> u'title': u'titleplaceholder'}]} 
> >>> urls = [x['url'] for x in json_data['bostock']]
> 
> >>> urls
> 
> [u'http://bl.ocks.org/mbostock/9360565', 
> 
> u'http://bl.ocks.org/mbostock/9265674', 
> 
> u'http://bl.ocks.org/mbostock/9265467', 
> 
> u'http://bl.ocks.org/mbostock/9234731', 

> u'http://bl.ocks.org/mbostock/9232962']
 
> Python loads the json in the file into a dictionary.  In this case, the 
> dictionary has a single key, 'bostock', and the value in the dictionary for 
 
> that key is a list (of dictionaries).  

> To get the urls, you need to get the list 
 
> json_data['bostock']
>  and then iterate over it's elements, getting the value for the key url for 
 > each one.  
> This is what the list comprehension 
> [x['url'] for x in json_data['bostock']]
> does.
> I hope that helps, 
> Kev

Kev your the man. Thanks
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PYTHON BASTARDS STILL CAN'T ANSWER THIS QUESTION:

[thrinaxodon666]

== 
>HOLY F*CKING GOD DAMNED NEWS! 
== 
> 
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> 
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> 
== 
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> 
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> 
THE MOST BEAUTIFUL KNEECAP EVER DISCOVERED. 
> 
I CALLED OUT CARTER N. 
> 
CARTER CAME RUSHING OVER. WE TOOK THE KNEECAP FROM THE INUIT SAVAGES AND FLEW 
TO THE SMITHSONIAN. 
> 
THEY CALLED US KOOKS AND SLAMMED THE DOOR. 
> 
== 
EVIDENCE THAT HUMANS LIVED IN THE DEVONIAN: 

https://groups.google.com/group/sci.bio.paleontology/browse_thread/thread/6f501c469c7af24f#
 
  
https://groups.google.com/group/sci.bio.paleontology/browse_thread/thread/3aad75c16afb0b82#
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Re: extract from json

[thrinaxodon666]

On Friday, March 7, 2014 3:27:27 PM UTC-5, tedd...@gmail.com wrote:
> I can't find any example on how to do this.
> 
> I have a json file like so:
> 
> {"bostock":[{"url":"http://bl.ocks.org/mbostock/9360565","title":"titleplaceholder","date":"dateplaceholder"},
> 
> {"url":"http://bl.ocks.org/mbostock/9265674","title":"titleplaceholder","date":"dateplaceholder"},
> 
> {"url":"http://bl.ocks.org/mbostock/9265467","title":"titleplaceholder","date":"dateplaceholder"},
> 
> {"url":"http://bl.ocks.org/mbostock/9234731","title":"titleplaceholder","date":"dateplaceholder"},
> 
> {"url":"http://bl.ocks.org/mbostock/9232962","title":"titleplaceholder","date":"dateplaceholder"},
> 
> 
> 
> this goes on for more than 700 entries. only thing unique is the number at 
> the end of the url. I am going to load the url in python, get the date and 
> title and write it in the json itself. 
> 
> Right now I am stuck on just reading the url in the json. Here is my code:
> 
> 
> 
> import json
> 
> 
> 
> with open("bostock.json") as json_file:
> 
> json_data = json.load(json_file)
> 
> print(json_data)
> 
> 
> 
> I have tried json_data[0], json_data.url and a few others I forget right now 
> and it does not seem to work.  
> 
> 
> 
> I have already figured out how to get the title and date.
> 
> First things first: How can i just get the url for each line of the above 
> json file?

I think it's better if you f*ck off.
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Re: Python programming

[William Ray Wing]

On Mar 7, 2014, at 1:03 PM, John Ladasky  wrote:

> 
> As for FORTRAN?  This week, I actually downloaded an application which 
> required a FORTRAN compiler.  This is the only FORTRAN application I've ever 
> needed.  It's not old code, the first revision came out about 10 years ago.  
> More than once, I have queried Google with the phrase "Why isn't FORTRAN dead 
> yet?"  For some reason, it lives on.  I can't say that I understand why.  
> -- 
> https://mail.python.org/mailman/listinfo/python-list

Well, I’d claim that for what it was designed for (FORTRAN stands for FORmula 
TRANslator after all), it is still pretty da*mn good.  It generates extremely 
fast, robust code that requires much less debugging effort than the equivalent 
C or C++ requires.  Most of the physicists I know still write FORTRAN, although 
they no longer do so exclusively.

Of course, as has been pointed out, the HUGE code base of scientific and 
numerical analysis code that already exists in FORTRAN makes rewriting sort of 
a waste of grant (or company) money.

-Bill
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Re: extract from json

[Chris Angelico]

On Sat, Mar 8, 2014 at 2:21 PM,   wrote:
> I think it's better if you (CENSORED) off.

Teddybubu, please understand that the above comment is from a spammer
and does not reflect the prevailing attitude of this list. I don't
like to make content-free posts like this, but as you already have the
answer you need, there's not a lot for me to add :)

ChrisA
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Re: Tuples and immutability

[Ian Kelly]

On Fri, Mar 7, 2014 at 7:17 PM, Gregory Ewing
 wrote:
> Here's another idea: If the __iadd__ method returns the
> same object, *and* the LHS doesn't have a __setitem__
> method, then do nothing instead of raising an exception.

Maybe it doesn't have a __setitem__ because the object that was
retrieved is computed rather than stored, and the result of the
__iadd__ will simply be discarded.  Somewhat contrived example:

class LessThanFilter:

def __init__(self, the_list):
self._the_list = the_list

def __getitem__(self, bound):
return [x for x in self._the_list if x < bound]


filter = LessThanFilter([10, 20, 30, 40, 50])
filter[25] += [15, 17, 23]

Should that last line not raise an exception?  The __iadd__ call will
return the same object, and the LHS doesn't have a __setitem__ method.

> I don't think that's a problem, because the use case
> being addressed is where the object performs in-place
> modification and always returns itself. Any object that
> doesn't return itself is not modifying in-place, even
> if the returned object happens to be equal to the
> original one.

I already mentioned this earlier in the thread, but a balanced binary
tree might implement += as node insertion and then return a different
object if the balancing causes the root node to change.
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Re: gdb unable to read python frame information

[dieter]

Wesley  writes:

> Install python from source with some special configure options?

When I last generated Python from source, there was no need
to do anything special to get debugging symbols (the option
("gcc") option "-g" was automatically included).

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Re: debugging on windows

[dieter]

Robin Becker  writes:

> Using
>
>> Python 3.3.3 (v3.3.3:c3896275c0f6, Nov 18 2013, 21:18:40) [MSC v.1600 32 bit 
>> (Intel)] on win32
>> Type "help", "copyright", "credits" or "license" for more information.
>
> to run a tkinter + pmw2 application I have the following error on windows xp 
> sp3
>
>> Unhandled exception at 0x1e0aebb8 in python.exe: 0xC005: Access 
>> violation reading location 0x0048.

This is a C level error -- likely some memory corruption.
You will need a C level debugger to analyse the problem -
and likely, it will not be easy.

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