Re: Fibonacci series recursion error
On Mon, 2 May 2011 06:49:41 +1000, Chris Angelico
ros...@gmail.com wrote:
: Sure. Serialize this Python object in a way that can be given to, say, PHP:
: foo={asdf:qwer,zxcv:1234}; foo[self]=[1,2,3,foo]
: Recurse from self into the list, recurse from there into a
: dictionary... Okay, that's a rather naive recursion and fraught with
: risk, but there are more complex examples. And watching for cyclic
: references would be O(N*N) as you'd need to maintain a full list of
: every PyObject* that you've sighted (talking here from the C API, but
: the same consideration applies whichever way you do it).
Wouldn't cyclic references give infinite recursion? And remain
infinitive if you recode it iteratively?
: I'm not sure that recursion is clearer. Recursion is a way of
: expressing the two rules:
:
: 1! = 1
: n! = n * (n-1)!
:
: But iteration is a way of expressing this equivalent rule:
:
: n! = 1 * 2 * 3 * ... * n-1 * n
:
: It really depends what you're trying to say.
True. There is a place for everything. However, in the example
above, you can map the recursive definition directly into python
without further ado. In order to express the one-liner in python,
as iteration, you need to introduce additional elements, namely
a state (index variable). Hence, recursion is clearer by being
close to the language you would normally use to describe the
problem.
--
:-- Hans Georg
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Re: Fibonacci series recursion error
On Mon, May 2, 2011 at 3:36 PM, Hans Georg Schaathun h...@schaathun.net wrote:
On Mon, 2 May 2011 06:49:41 +1000, Chris Angelico
ros...@gmail.com wrote:
: Sure. Serialize this Python object in a way that can be given to, say, PHP:
: foo={asdf:qwer,zxcv:1234}; foo[self]=[1,2,3,foo]
Wouldn't cyclic references give infinite recursion? And remain
infinitive if you recode it iteratively?
Well, I don't know of a decent non-recursive way to process a
recursive structure. Incidentally, this example is almost directly
from some working code of ours; I have a C function that recurses over
a Python dictionary and aborts as soon as it's found too much data
(for a fairly arbitrary definition of too much, but one that's
deliberately designed to prevent infinite recursion). Since every
element in the dictionary can be a list/dict, and every element of
those can be too, there's no non-recursive way to do it, other than by
doing the recursion yourself:
# partly pseudocode
searchme=[foo]
while len(searchme):
cur=get_next_elem(searchme[-1])
if cur==end_of_list: searchme[-1:]=[]
else: if can_be_recursed_into(cur): searchme.append(cur)
else: output(cur)
This would work, more or less, but it merely trades true recursion
for the searchme[] stack. Yes, it's iterative. No, it hasn't abolished
recursion.
True. There is a place for everything. However, in the example
above, you can map the recursive definition directly into python
without further ado. In order to express the one-liner in python,
as iteration, you need to introduce additional elements, namely
a state (index variable). Hence, recursion is clearer by being
close to the language you would normally use to describe the
problem.
True, and you could abolish a lot of temporary variables by turning
them into parameters to recursive calls. But you've abolished nothing.
The recursive factorial is very similar to:
reduce(`*,range(1,n+1))
The iterative is very similar to:
reduce(`*,xrange(1,n+1))
One of 'em stacks up all the numbers and the other gets 'em as it
needs 'em. Fundamentally, there's really not a lot of difference. By
piling up the numbers on your stack, you just change the format of
your saved state, you don't actually save anything.
Chris Angelico
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Re: Fibonacci series recursion error
On Mon, May 2, 2011 at 4:28 PM, Chris Angelico ros...@gmail.com wrote: reduce(`*,range(1,n+1)) reduce(`*,xrange(1,n+1)) Whoops, forgot which language I was using. Back-tick functions not being available, these need to be: reduce(operator.mul,range(1,n+1)) reduce(operator.mul,xrange(1,n+1)) Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
Re: Py_INCREF() incomprehension
hello, Thomas, Gregory, thank you for your ansrwers, I guess this is the point where yo should start printf programing. oh', already done :) * What happens during module initialization? successfully initialized, * What happens n the functions? * Where does the stuff fail? * What are the reference counts of the involved objects? sorry for the dumb question: how can I controll number of reference in C? PyModule_AddObject(o, error, cibcrypt_error_nokey); Py_INCREF(cibcrypt_error_nokey); and now if there is some expected exception, I get it. Any explanation? I don't have one - I would think that if the module object exists for all the time, it would be enough to have one reference there. But obviously it is not enough - did you at any time del something related to here? The module or one of its attributes? Anyway, it seems safer to do INCREF here - so do it. (As Gregory already stated - it looks cleaner if you do INCREF before AddObject.) ok, ps: this is just for my passion, but I would like to understand it very-very much :) Understandable. That's that the printf debugging of the refcounts can be good for - even if you don't really have a problem. thanks, I'll go to read the docs :) bye: a. -- http://mail.python.org/mailman/listinfo/python-list
Re: Compile 32bit C-lib on 64 bit
Hello, thanks for all reply, On Mon, May 02, 2011 at 03:20:40AM +0100, Nobody wrote: You need to build your module for a 32-bit version of Python. ok, I believed it, I was hoping there is another solution, On a 64-bit system, each process is either 32-bit or 64-bit process. You can't mix 32-bit code and 64-bit code in a single process. If you have to use that library and you only have a 32-bit version of it, then everything else must also be 32-bit: the Python interpreter, your binary module, and all of the libraries which it uses. ok, thank you, a. -- http://mail.python.org/mailman/listinfo/python-list
Re: Py_INCREF() incomprehension
Hegedüs, Ervin, 02.05.2011 08:41: Thomas, I guess this is the point where yo should start printf programing. oh', already done :) FWIW, Cython 0.14+ has special support for gdb now, so, in addition to print and printf debugging, you can also use gdb to explore the state of your application, be it at the Python, Cython or C level. http://docs.cython.org/src/userguide/debugging.html Stefan -- http://mail.python.org/mailman/listinfo/python-list
Re: Development tools and practices for Pythonistas
On Monday 02 May 2011 13:22:44 Ben Finney wrote: rusi rustompm...@gmail.com writes: You may want to look at rcs if you are in the space where But today, Bazaar or Mercurial fill that role just as well: quick simple set up, good tool support (yes, even in Emacs using VC mode), and easy to use for easy things. Actually, Bazaar is more convenient than rcs for a single user, as the repository can be the working directory (with a hidden .bzr directory that stores diffs). I had to use git, too, because some projects use git for their version control (viz PySide, Nokia's tool to replace PyQt). IMHO there is not much to pick between git and Bazaar and hg is also rather similar. The remaining doubts are betwwed the Distributed Version Control and the more traditional Subversion, which is also quite nice, even for a single user. OldAl. -- Algis http://akabaila.pcug.org.au/StructuralAnalysis.pdf -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On Apr 30, 11:14 am, Peter Otten __pete...@web.de wrote: For the record, the one true way to implement the Fibonacci series in Python is def fib(): ... a = b = 1 ... while True: ... yield a ... a, b = b, a+b # look ma, no temporary variable Not any claim to 'the one true pythonic way' but fib can be written in a clean recursive way with linear space-time behavior asz follows: Dijkstra explained that fib is an 2nd order recurrence -- fib(n) defined in terms of fib (n-1) and fib(n-2) whereas programming loops and recursion are 1st order -- state at iteration n defines state at iteration n+1. Converting the 2nd order fib relation to a 1st order one trivially gives a linear program. The key insight from Dijkstra is that all we need to do is to move from a recursive function returning fibonacci nos to one returning pairs of adjacent ones. def fibpair(n): # returns (fib(n), fib(n+1)) if n==0: return (1,1) else: (a,b) = fibpair(n-1) return (b, a+b) After that fib is just this: def fib(n): a,b = fibpair(n) return a; -- http://mail.python.org/mailman/listinfo/python-list
Re: Development tools and practices for Pythonistas
On May 2, 12:08 pm, Algis Kabaila akaba...@pcug.org.au wrote: Actually, Bazaar is more convenient than rcs for a single user, as the repository can be the working directory (with a hidden .bzr directory that stores diffs). Dont exactly understand... Is it that you want it specifically hidden? Otherwise rcs will look inside an RCS directory just as bzr will with .bzr git will with .git and so on. -- http://mail.python.org/mailman/listinfo/python-list
Re: PIL Question
[PyNewbie] Question: I can't seem to find the captured image, where does it go? for me, it just goes to the current working directory: $ python -i Python 2.5.4 (r254:67916, Dec 23 2008, 15:10:54) [MSC v.1310 32 bit (Intel)] on win32 Type help, copyright, credits or license for more information. from PIL import ImageGrab ImageGrab.grab().save(screen_capture.jpg, JPEG) import os os.listdir(os.getcwd()) ['.appcfg_cookies', '.appcfg_nag', '.bash_history', '.idlerc', '.inputrc', '.povray', 'bootex.log', 'buildBasicDemo.txt', 'glsample.cpp', 'glsample.o', 'log.txt', 'screen_capture.jpg', 'test.c'] -- nirinA -- http://mail.python.org/mailman/listinfo/python-list
Re: Development tools and practices for Pythonistas
On Monday 02 May 2011 17:19:57 rusi wrote: On May 2, 12:08 pm, Algis Kabaila akaba...@pcug.org.au wrote: Actually, Bazaar is more convenient than rcs for a single user, as the repository can be the working directory (with a hidden .bzr directory that stores diffs). Dont exactly understand... Is it that you want it specifically hidden? Otherwise rcs will look inside an RCS directory just as bzr will with .bzr git will with .git and so on. Sorry for not being clear - ls will not show directories that start with . - in that sense these directories are hidden. They are not really really hidden, as ls -l will show them. They simply are not in the way and keep the progressive versions of the program (in form of diffs). Does that make better sense?. -- Algis http://akabaila.pcug.org.au/StructuralAnalysis.pdf -- http://mail.python.org/mailman/listinfo/python-list
Re: What other languages use the same data model as Python?
On Sun, 2011-05-01, Terry Reedy wrote: On 5/1/2011 4:45 AM, Steven D'Aprano wrote: ... What other languages use the same, or mostly similar, data model as Python? Natural languages. That is why I think it is better to think of Python as an algorithm language or information-object manipulation language rather than as just a linear-memory machine language.A linear memory with bytes addressed from 0 to max-int or max-long is an explicit part of the definition of assembly languages and C. It is no part of the definition of Python. It's not part of the definition of C either -- C supports segmented memory (pre-386 Intel) and separate code/data address spaces. (Even if most C users tend not to think of it that way.) /Jorgen -- // Jorgen Grahn grahn@ Oo o. . . \X/ snipabacken.se O o . -- http://mail.python.org/mailman/listinfo/python-list
build the sql where cause dynamic
Hi,
from some radio buttons in a django app i concat string like that:
But have no idea how i get the or when there different values
for a specified p column (# is currently my intended splitter maybe i
can concat a better input?).
input: p2=1#p2=2#p1=3#p1=1#p1=5#pc=1#py=1
output: p2 in ('1','2') and p1 in ('3','1','5') and pc in ('1') and
py in ('1')
Many thanks for any starting point
Christian
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Re: build the sql where cause dynamic
On Mon, May 2, 2011 at 5:48 PM, christian oz...@web.de wrote:
Hi,
from some radio buttons in a django app i concat string like that:
But have no idea how i get the or when there different values
for a specified p column (# is currently my intended splitter maybe i
can concat a better input?).
input: p2=1#p2=2#p1=3#p1=1#p1=5#pc=1#py=1
output: p2 in ('1','2') and p1 in ('3','1','5') and pc in ('1') and
py in ('1')
Start by splitting the string and iterating:
for el in input.split('#'):
(obviously your variable won't want to be called 'input' but you knew
that already)
Then split on the = sign and add to a list or dictionary. Be wary of
elements that don't have an equals sign in them.
That looks like the querystring straight from the GET form, where
you're using tickboxes. You could quite happily use '' as your
primary delimiter, if that's the case.
Chris Angelico
--
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Re: How to build an application in Django which will handle Multiple servers accross network
Hi All, Thanks for the resposes. I think I was not able to communicate my problem very well. Here I am not managing any network devices, what i am doing is getting some info from various servers on netowrk. I don't know how to explain what kind of info is needed, but for the time if you just assume that a driver for windows and linux is already written which has command line interface too which gets certain info about server. Now the information returned by this driver software from each server is to be shown at a common place. For this I am planning a web based application that can connect to each individual server and get the info and show it on UI. For this to happen i need some interface to which my web based application (to be developed in Django and Python) can connect to each server in network and call the driver methods on that server to get the info. I hope now i am clear with my thoughts. Please mail me back if still I am not clear. The solutions I got 1. Using WMI on windows but how it will work on Linux?. 2. Pyro which supports remote objects. 3. Open NMS - it is a java based open source project, we don't have any expertise in java... I want something that can be integrated with python and django. 4. ZenOSS - It is for managing some IP based devices on network.. I don't know how it will help me. Please give me some ideas on python even it needs some development effort. Regards, Anurag On Apr 29, 5:21 pm, Adam Tauno Williams awill...@whitemice.org wrote: On Fri, 2011-04-29 at 13:24 +0200, Paul Kölle wrote: Am 29.04.2011 12:01, schrieb Adam Tauno Williams: 3. The web based application will be used internally in the network to moniter servers in that network only. You mean like OpenNMS or ZenOSS? 4. Web based application will be a real time application with a Database. Like OpenNMS or ZenOSS? How can they be realtime if they generate static images? All images are static regardless of how much they pretend not to be. You can refresh as much as you like. But a graph shows a progression over time so there is always an interval. 5. Technology I am thingking for web based application is Django and Python as this web application can also be installed on Windows or Linux based OS. If you want real-time monitoring you *must* build a service; a 'web app' can *not* do that. Do you mean an agent? No, just use WMI over the wire. Agents are terrible, hard to develop, unreliable, and everyone hates agents. The systems already provide you access to the information you are talking about. 6. Also please suggest which third party tool for chatrs and graphs I should use with Django (open source + paid) ZenOSS and OpenNMS do graphs using RRD. I know this is the standard but IMO it's totally backward these days. Correlating or selecting/deselecting certain values is painful (you have to write a graph def) How is it painful? Of course you have to create a graph definition - in your case you are creating a graph definition BY WRITING CODE! There couldn't be a more painful way to just create a graph. Have you used recent versions of ZenOSS? Graph definitions can be created right in the UI. . With canvas and modern JS libs like raphael there are better ways to do this. Just look at google analytics. I've seen it. I don't see how it is better. It's a graph. It looks like PCP (http://oss.sgi.com/projects/pcp/features.html) will gain a JSON interface shortly. That would be awesome because PCP is developed by real engineers and has a proper architecture and is NOT a CPU sucking monstrosity of PERL-line-noise + a few hacked-together PHP frontends. I have no idea where the PERL-line-noise + a few hacked-together PHP frontend comment comes from. RRD is written in C. OpenNMS is Java and ZenOSS is Python/ZOPE. And as for CPU sucking monstrosity that is what everyone says... until they try to build a monitoring application... and thus create their own CPU sucking monstrosity. This is a case of those-who-refuse-to-use-are-doomed-to-reinvent. -- http://mail.python.org/mailman/listinfo/python-list
HI
Hello, Could you please help me with the modeling in Python the following problem: (e.g., g_t means g with index t) Min∑_(i=1)^n▒∑_(t=1)^l▒[s_i (t)-min[s ̂_i (t)×α_t×exp(g_t ),C_i (t) ] ]^2 subject to s_i (t)=f_i (t)[S_i+f_(i-1) (t)[S_(i-1)+f_(i-2) (t)[S_(i-2)+⋯f_2 (t) [S_2+f_1 (t) S_1 ]…] ] ][1-f_(i+1) (t)] f_i (t)=F_i (t)-F_i (t-1) F_i (t)=(((1-e^(-(X_i (t)-X_i (0) )(p_i+q_i ) )))/(((q_i⁄p_i ) e^(- (X_i (t)-X_i (0) )(p_i+q_i ) )+1)), if t≥τ_i and F_i (t)=0 if tτ_i X_i (t)=(t-τ_i+1)+ln(〖pr〗_i (t)/〖pr〗_i (0))β α_t≥0, g_t=const 0p_i1, 0q_i1 S_i0, ∀i=1,2,…,n Where s ̂_i (t)=p_i S_i +(q_i-p_i ) s_i (t-1)-(q_i/S_i ) [s_i (t-1) ]^2, S_i=μ_i (t)M_i -- http://mail.python.org/mailman/listinfo/python-list
Re: HI
Here we need to estimate p_i, q_i, and β. Thank you, Min∑_(i=1)^n▒∑_(t=1)^l▒[s_i (t)-min[s ̂_i (t)×α_t×exp(g_t ),C_i (t) ] ]^2 subject to s_i (t)=f_i (t)[S_i+f_(i-1) (t)[S_(i-1)+f_(i-2) (t)[S_(i-2)+⋯f_2 (t) [S_2+f_1 (t) S_1 ]…] ] ][1-f_(i+1) (t)] f_i (t)=F_i (t)-F_i (t-1) F_i (t)=(((1-e^(-(X_i (t)-X_i (0) )(p_i+q_i ) )))/(((q_i⁄p_i ) e^(- (X_i (t)-X_i (0) )(p_i+q_i ) )+1)), if t≥τ_i and F_i (t)=0 if tτ_i X_i (t)=(t-τ_i+1)+ln(〖pr〗_i (t)/〖pr〗_i (0))β α_t≥0, g_t=const 0p_i1, 0q_i1 S_i0, ∀i=1,2,…,n Where s ̂_i (t)=p_i S_i +(q_i-p_i ) s_i (t-1)-(q_i/S_i ) [s_i (t-1) ]^2, S_i=μ_i (t)M_i -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On Apr 30, 12:18 pm, Steven D'Aprano steve +comp.lang.pyt...@pearwood.info wrote: The number of calls is given by a recursive function with a similar form as that of Fibonacci. As far as I know, it doesn't have a standard name, but I'll call it R(n): R(n) = R(n-1) + R(n-2) + 1, where R(0) = R(1) = 1 Changing your definition slightly to the following: def r(n): if n==0 or n==1: return 0 else: return r(n-1) + r(n-2) + 1 This r counts the number of times the '+' is done in the original (naive) fib. We see it is the same as fib (off by 1) [fib(n) for n in range(10)] [1, 1, 2, 3, 5, 8, 13, 21, 34, 55] [r(n) for n in range(10)] [0, 0, 1, 2, 4, 7, 12, 20, 33, 54] So it does not need a new name :-) -- http://mail.python.org/mailman/listinfo/python-list
Re: Compile 32bit C-lib on 64 bit
On Sun, 2011-05-01, Hegedüs Ervin wrote: Hello, this is not a clear Python question - I've wrote a module in C, which uses a 3rd-party lib - it's a closed source, I just get the .so, .a and a header file. Looks like it works on 32bit (on my desktop), but it must be run on 64bit servers. When I'm compiling it on 64bit, gcc says: /usr/bin/ld: skipping incompatible /lib32/lib3rdpartyCrypt.so when searching for -l3rdpartyCrypt A different angle: if you need to use closed-source, non-standard crypto, and the suppliers cannot even be bothered to compile it for the CPU architecture that has been standard for at least 6--7 years, start planning to replace it *now*. /Jorgen -- // Jorgen Grahn grahn@ Oo o. . . \X/ snipabacken.se O o . -- http://mail.python.org/mailman/listinfo/python-list
Re: What other languages use the same data model as Python?
Dennis Lee Bieber wlfr...@ix.netcom.com wrote: As I recall from my programming language design class (only and intro, it was so small we met in a meeting room rather than classroom), ALGOL was described as call by name; It is true that Algol had 'call by name', but (at least the Algol-W that I learned) also supported 'call by value' and 'call by reference'. The danger of course was that call by name was the default mechanism so you could end up using it accidentally. I remember we had one class where we had to work out (by hand) the output of a program which used call by name to alias I and A[I] in some recursive calls. Not nice. Fortunately even at that time it was mostly being taught as an oddity; real programming was of course done in Algol 68C or BCPL. -- Duncan Booth http://kupuguy.blogspot.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On Mon, 02 May 2011 01:27:39 -0700, rusi wrote: On Apr 30, 12:18 pm, Steven D'Aprano steve +comp.lang.pyt...@pearwood.info wrote: The number of calls is given by a recursive function with a similar form as that of Fibonacci. As far as I know, it doesn't have a standard name, but I'll call it R(n): R(n) = R(n-1) + R(n-2) + 1, where R(0) = R(1) = 1 Changing your definition slightly to the following: def r(n): if n==0 or n==1: return 0 else: return r(n-1) + r(n-2) + 1 Except that's not the same as my R(n). The base cases should be 1, not 0. That makes rather a big difference to the value: by n = 35, you have R(35) = 29860703 fib(35) = 9227465 or nearly 2.25 times greater. And the difference just keeps getting bigger... We see it is the same as fib (off by 1) [...] So it does not need a new name :-) I see your smiley, but there are a number of similar series as Fibonacci, with the same recurrence but different starting values, or similar but slightly different recurrences. E.g. Lucas, primefree, Pell, Padovan and Perrin numbers. (The fact that most of those start with P is almost certainly a coincidence.) -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Development tools and practices for Pythonistas
On May 2, 9:48 am, Algis Kabaila akaba...@pcug.org.au wrote: On Monday 02 May 2011 17:19:57 rusi wrote: On May 2, 12:08 pm, Algis Kabaila akaba...@pcug.org.au wrote: Actually, Bazaar is more convenient than rcs for a single user, as the repository can be the working directory (with a hidden .bzr directory that stores diffs). Dont exactly understand... Is it that you want it specifically hidden? Otherwise rcs will look inside an RCS directory just as bzr will with .bzr git will with .git and so on. Sorry for not being clear - ls will not show directories that start with . - in that sense these directories are hidden. They are not really really hidden, as ls -l will show them. They simply are not in the way and keep the progressive versions of the program (in form of diffs). ls -l will not show directories that start with .. ls -a will. Regards Jacek -- http://mail.python.org/mailman/listinfo/python-list
codec for UTF-8 with BOM
Hi! I want to write a file starting with the BOM and using UTF-8, and stumbled across some problems: 1. I would have expected one of the codecs to be 'UTF-8 with BOM' or something like that, but I can't find the correct name. Also, I can't find a way to get a list of the supported codecs at all, which strikes me as odd. 2. I couldn't find a way to write the BOM either. Writing codecs.BOM doesn't work, as it is an already encoded byte string. Of course, I can write u'\ufeff', but I'd rather avoid such magic numbers in my code. 3. The docs mention encodings.utf_8_sig, available since 2.5, but I can't locate that thing there either. What's going on here? What would you do? Uli -- Domino Laser GmbH Geschäftsführer: Thorsten Föcking, Amtsgericht Hamburg HR B62 932 -- http://mail.python.org/mailman/listinfo/python-list
Re: Deditor
Yes On Mon, May 2, 2011 at 2:12 AM, Kruptein darragh@gmail.com wrote: On 1 mei, 17:50, Alec Taylor alec.tayl...@gmail.com wrote: Traceback (most recent call last): File O:\deditor\deditor\deditor.py, line 7, in modul e import wx, os, datetime, sys, ConfigParser, wx.aui, wx.lib.scrolledpanel File C:\Python27\lib\site-packages\wx-2.8-msw-unicode\wx\__init__.py, line 4 5, in module from wx._core import * File C:\Python27\lib\site-packages\wx-2.8-msw-unicode\wx\_core.py, line 4, i n module import _core_ ImportError: DLL load failed: %1 is not a valid Win32 application. On Mon, May 2, 2011 at 12:33 AM, Kruptein darragh@gmail.com wrote: On 1 mei, 10:59, Alec Taylor alec.tayl...@gmail.com wrote: Maybe I'm missing something, but I downloaded the zip file and ran each .py and .pyc file in turn, but none brought up the nicededitor GUI I've seen screenshots of... On the other subject, did you have a preference to what installer I should code for it? - InnoSetup (exe), NSIS (exe) or MSI (.msi) not a msi, for the rest it doesn't matter :), on my windows if you rundeditor.py it should launch however you need to have the wxpython-2.8 package installed, what happens if you rundeditor.py from console? -- http://mail.python.org/mailman/listinfo/python-list that looks like you have installed the wxpython module wrongly. Have you downloaded the version that matches your python version? -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: codec for UTF-8 with BOM
On Mon, May 2, 2011 at 1:34 AM, Ulrich Eckhardt
ulrich.eckha...@dominolaser.com wrote:
Hi!
I want to write a file starting with the BOM and using UTF-8, and stumbled
across some problems:
1. I would have expected one of the codecs to be 'UTF-8 with BOM' or
something like that, but I can't find the correct name. Also, I can't find a
way to get a list of the supported codecs at all, which strikes me as odd.
If nothing else, there's
http://docs.python.org/library/codecs.html#standard-encodings
The correct name, as you found below and as is corroborated by the
webpage, seems to be utf_8_sig:
uFOøbar.encode('utf_8_sig')
'\xef\xbb\xbfFO\xc3\xb8bar'
This could definitely be documented more straightforwardly.
snip
3. The docs mention encodings.utf_8_sig, available since 2.5, but I can't
locate that thing there either. What's going on here?
Works for me™:
Python 2.6.6 (r266:84292, Jan 12 2011, 13:35:00)
[GCC 4.2.1 (Apple Inc. build 5664)] on darwin
Type help, copyright, credits or license for more information.
from encodings import utf_8_sig
Cheers,
Chris
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Re: Fibonacci series recursion error
On 02 May 2011 01:09:21 GMT, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: : Ah, I see where you're coming from now! You think I'm arguing *against* : the use of recursion. Not at all. Earlier in this thread, I said: Fair enough. Somebody said something about recursion mainly being a beginner's error. I don't think it was you, but I felt that your argument in context mainly served to reinforce such a view, whether intended or not. : Consequently, the naive recursive function is ridiculously slow and : memory-hungry. : : This seems to have give rise to a myth that recursion should be avoided. : What needs to be avoided is *badly thought out* recursion. Then we agree. And badly thought-out iteration is as bad as badly thought-out recursion. : To be honest, I don't know what Python does with local variables. But I : *guess* it uses a constant-sized record which points to the locals, : because that's how I'd do it :) Maybe, but would it be able to treat specially C API functions with a large chunk of stack memory used for local variables? : Given a choice between a complicated iterative algorithm and a simple : recursive version, there's no prima facie reason to expect the recursive : version to *necessarily* be slower than iteration in Python *merely* : because it uses recursion. As always, if speed is an issue, profile and : identify the bottlenecks before deciding how to fix them. Then we are on the same page. And it is becoming increasingly clear how bizarre this discussion is in a python context. The overhead which may be caused by recursion in hardware is only one of many sources of overhead which one accepts when opting to use python in order to gain other benefits. -- :-- Hans Georg -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On 02 May 2011 08:56:57 GMT, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: : I see your smiley, but there are a number of similar series as Fibonacci, : with the same recurrence but different starting values, or similar but : slightly different recurrences. E.g. Lucas, primefree, Pell, Padovan and : Perrin numbers. Well, Fibonacci isn't one unique sequence. Any sequence satisfying f(n) = f(n-1) + f(n-2) is /a/ Fibonacci sequence. Regardless of starting values. At least according to some authors. Ian Andersen (A First Course in Combinatorial Mathematics) prefer the sequence 1,2,3,5 ... Cormen, Leiserson, Rivest (Introduction to Algorithms) prefer 0,1,1,2, ... (although they also start the indexing at 0). Penguin, Dict. of Mathematics prefer 1,1,2,3,5 but they also suggest 0,1,1,2,3, ... In short, don't assume that a person talking about Fibonacci numbers assume the same base cases as you do. -- :-- Hans Georg -- http://mail.python.org/mailman/listinfo/python-list
Re: codec for UTF-8 with BOM
On Monday, 2 May 2011 19:47:45 UTC+10, Chris Rebert wrote:
On Mon, May 2, 2011 at 1:34 AM, Ulrich Eckhardt
ulrich@dominolaser.com wrote:
The correct name, as you found below and as is corroborated by the
webpage, seems to be utf_8_sig:
uFOøbar.encode('utf_8_sig')
'\xef\xbb\xbfFO\xc3\xb8bar'
To complete the picture, decoding swallows the BOM:
'\xef\xbb\xbfFO\xc3\xb8bar'.decode('utf_8_sig')
u'FO\xf8bar'
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Re: build the sql where cause dynamic
On 2 Mai, 10:13, Chris Angelico ros...@gmail.com wrote:
On Mon, May 2, 2011 at 5:48 PM, christian oz...@web.de wrote:
Hi,
from some radio buttons in a django app i concat string like that:
But have no idea how i get the or when there different values
for a specified p column (# is currently my intended splitter maybe i
can concat a better input?).
input: p2=1#p2=2#p1=3#p1=1#p1=5#pc=1#py=1
output: p2 in ('1','2') and p1 in ('3','1','5') and pc in ('1') and
py in ('1')
Start by splitting the string and iterating:
for el in input.split('#'):
(obviously your variable won't want to be called 'input' but you knew
that already)
Then split on the = sign and add to a list or dictionary. Be wary of
elements that don't have an equals sign in them.
That looks like the querystring straight from the GET form, where
you're using tickboxes. You could quite happily use '' as your
primary delimiter, if that's the case.
Chris Angelico
Many Thanks
Christian
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Re: Development tools and practices for Pythonistas
On Monday 02 May 2011 19:09:38 jacek2v wrote: On May 2, 9:48 am, Algis Kabaila akaba...@pcug.org.au wrote: On Monday 02 May 2011 17:19:57 rusi wrote: On May 2, 12:08 pm, Algis Kabaila akaba...@pcug.org.au wrote: Actually, Bazaar is more convenient than rcs for a single user, as the repository can be the working directory (with a hidden .bzr directory that stores diffs). Dont exactly understand... Is it that you want it specifically hidden? Otherwise rcs will look inside an RCS directory just as bzr will with .bzr git will with .git and so on. Sorry for not being clear - ls will not show directories that start with . - in that sense these directories are hidden. They are not really really hidden, as ls -l will show them. They simply are not in the way and keep the progressive versions of the program (in form of diffs). ls -l will not show directories that start with .. ls -a will. Regards Jacek Thanks - you are right - pardon my absent mindedness. -- Algis http://akabaila.pcug.org.au/StructuralAnalysis.pdf -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On May 2, 2:53 pm, Hans Georg Schaathun h...@schaathun.net wrote: On 02 May 2011 08:56:57 GMT, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: : I see your smiley, but there are a number of similar series as Fibonacci, : with the same recurrence but different starting values, or similar but : slightly different recurrences. E.g. Lucas, primefree, Pell, Padovan and : Perrin numbers. Well, Fibonacci isn't one unique sequence. Any sequence satisfying f(n) = f(n-1) + f(n-2) is /a/ Fibonacci sequence. Regardless of starting values. At least according to some authors. And they all will, when expressed in closed form, be of the form f(n) = phi^n + something of a smaller order where phi = (1 + sqrt(5))/2 Since phi 1 they are exponential, ignoring lower order terms. -- http://mail.python.org/mailman/listinfo/python-list
Re: codec for UTF-8 with BOM
Chris Rebert wrote: 3. The docs mention encodings.utf_8_sig, available since 2.5, but I can't locate that thing there either. What's going on here? Works for me™: Python 2.6.6 (r266:84292, Jan 12 2011, 13:35:00) [GCC 4.2.1 (Apple Inc. build 5664)] on darwin Type help, copyright, credits or license for more information. from encodings import utf_8_sig This works for me, too. What I tried and what failed was import encodings encodings.utf_8_sig which raises an AttributeError or dir(encodings), which doesn't show the according element. If I do it your way, the encoding then shows up in the content of the module. Apart from the encoding issue, I don't understand this behaviour. Is the module behaving badly or are my expectations simply flawed? Thanks! Uli -- Domino Laser GmbH Geschäftsführer: Thorsten Föcking, Amtsgericht Hamburg HR B62 932 -- http://mail.python.org/mailman/listinfo/python-list
Re: HI
anvar wrote:
Could you please help me with the modeling in Python the following
problem: (e.g., g_t means g with index t)
Typically, you would use either a list or a dict to simulate something like
that:
# list
g = [1, 2, 4, 8, 16]
print g[3]
# dictionary
h = {}
h[0] = 1
h[1] = 2
h[2] = 4
h[3] = 8
h[4] = 16
print h[3]
The difference is that a list needs elements starting at index 0 and without
any gaps, while a dictionary can contain holes. Please refer to any
beginners' Python tutorial for info on these types.
Concerning the other formulas you posted, those ended up as completely
illegible here for the complete lack of formatting. Explaining things in
plain English along with the mathematics would be a good idea, IMHO.
Good luck!
Uli
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Geschäftsführer: Thorsten Föcking, Amtsgericht Hamburg HR B62 932
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Re: codec for UTF-8 with BOM
Ulrich Eckhardt wrote: Chris Rebert wrote: 3. The docs mention encodings.utf_8_sig, available since 2.5, but I can't locate that thing there either. What's going on here? Works for me™: Python 2.6.6 (r266:84292, Jan 12 2011, 13:35:00) [GCC 4.2.1 (Apple Inc. build 5664)] on darwin Type help, copyright, credits or license for more information. from encodings import utf_8_sig This works for me, too. What I tried and what failed was import encodings encodings.utf_8_sig which raises an AttributeError or dir(encodings), which doesn't show the according element. If I do it your way, the encoding then shows up in the content of the module. Apart from the encoding issue, I don't understand this behaviour. Is the module behaving badly or are my expectations simply flawed? This is standard python package behaviour: import logging logging.handlers Traceback (most recent call last): File stdin, line 1, in module AttributeError: 'module' object has no attribute 'handlers' import logging.handlers logging.handlers module 'logging.handlers' from '/usr/lib/python2.6/logging/handlers.pyc' You wouldn't see the AttributeError only if encodings/__init__.py contained a line from . import utf_8_sig or similar. The most notable package that acts this way is probably os which eagerly imports a suitable path module depending on the platform. As you cannot foresee which encodings are actually needed in a script it makes sense to omit a just-in-case import. -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error (slightly OT)
On 01/-10/-28163 02:59 PM, Chris Angelico wrote: On Mon, May 2, 2011 at 3:36 PM, Hans Georg Schaathunh...@schaathun.net wrote: On Mon, 2 May 2011 06:49:41 +1000, Chris Angelico ros...@gmail.com wrote: : Sure. Serialize this Python object in a way that can be given to, say, PHP: : foo=asdf:qwer,zxcv:1234}; foo[self]=[1,2,3,foo] Wouldn't cyclic references give infinite recursion? And remain infinitive if you recode it iteratively? Well, I don't know of a decent non-recursive way to process a recursive structure. Incidentally, this example is almost directly from some working code of ours; I have a C function that recurses over a Python dictionary and aborts as soon as it's found too much data (for a fairly arbitrary definition of too much, but one that's deliberately designed to prevent infinite recursion). snip Chris Angelico When iterating over a repeatable, potentially infinite sequence of distinguishable values, you can safely detect infinitude ;-) (cycles) with a linear overhead (rather than n-squared). Given a sequence, create two iterators for it. Start them both at the same point, but iterate the second one twice for every time you iterate the first one. If the two ever get the same value, you have a cycle. In the case of Python objects, you probably want to use an 'is' comparison, rather than comparing id() for equal. But the concept works, and easily. DaveA -- http://mail.python.org/mailman/listinfo/python-list
Re: HI
anvar wrote: Hello, Could you please help me with the modeling in Python the following problem: (e.g., g_t means g with index t) Min∑_(i=1)^n▒∑_(t=1)^l▒[s_i (t)-min[s ̂_i (t)×α_t×exp(g_t ),C_i (t) ] ]^2 subject to s_i (t)=f_i (t)[S_i+f_(i-1) (t)[S_(i-1)+f_(i-2) (t)[S_(i-2)+⋯f_2 (t) [S_2+f_1 (t) S_1 ]…] ] ][1-f_(i+1) (t)] f_i (t)=F_i (t)-F_i (t-1) F_i (t)=(((1-e^(-(X_i (t)-X_i (0) )(p_i+q_i ) )))/(((q_i⁄p_i ) e^(- (X_i (t)-X_i (0) )(p_i+q_i ) )+1)), if t≥τ_i and F_i (t)=0 if tτ_i X_i (t)=(t-τ_i+1)+ln(〖pr〗_i (t)/〖pr〗_i (0))β α_t≥0, g_t=const 0p_i1, 0q_i1 S_i0, ∀i=1,2,…,n Where s ̂_i (t)=p_i S_i +(q_i-p_i ) s_i (t-1)-(q_i/S_i ) [s_i (t-1) ]^2, S_i=μ_i (t)M_i Hi, Nice joke. JM -- http://mail.python.org/mailman/listinfo/python-list
Re: What other languages use the same data model as Python?
On 2011-05-02, Jorgen Grahn grahn+n...@snipabacken.se wrote: On Sun, 2011-05-01, Terry Reedy wrote: On 5/1/2011 4:45 AM, Steven D'Aprano wrote: ... What other languages use the same, or mostly similar, data model as Python? Natural languages. That is why I think it is better to think of Python as an algorithm language or information-object manipulation language rather than as just a linear-memory machine language.A linear memory with bytes addressed from 0 to max-int or max-long is an explicit part of the definition of assembly languages and C. It is no part of the definition of Python. It's not part of the definition of C either -- C supports segmented memory (pre-386 Intel) and separate code/data address spaces. (Even if most C users tend not to think of it that way.) Indeed. All the C compilers I used for many years (on both PDP-11 and 80286 under Unix) assumed a segmented memory space with separate data and text addresses spaces. More recently, the same can be said for AVR and many other Harvard architecture machines. The linear memory with bytes addressed from 0 to max-int or max-long thing is merely an implicit assumption made by bad C programmers. -- Grant -- http://mail.python.org/mailman/listinfo/python-list
Re: HI
Dear Ulrich Eckhardt and Jean-Michel Pichavant! First of all thank you for your attention. I'have never expected to receive response. Actually, I am doing my internship in Marketing Division in small company., I got this assignment yesterday morning. My boss wants perfect technology diffusion based forecasting model. I found the required model, modified it..but cannot solve it (university friend suggested Python because it had special tools for optimization). I will appreciate if you help me to find right tools and give some more advises. Thank you for your precious time. As to problem, I should use nonlinear least-square estimation methodology (to estimate p_i, q_i, and β parameters) where the objective of the estimation procedure is minimization of the sum of squared error. Here in problem: F_i (t) the cumulative density function at time t for technology generation i f_i (t) the probability density function at time t for technology generation i p_i the proportion of mass media communication for generation i q_i the proportion of word of mouth for generation i μ_i (t) the market share at time t for generation i (data exists) M_i total market potential for generation i, (data exists) S_i total sales potential for generation i, S_i=μ_i (t)M_i τ_i the introduction time for generation i, τ_i≥1 (data exists) s_i (t) the actual sales of products at time t for generation i (data exists) s ̂_i (t) the estimated sales of products at time t for generation i X_i (t) the cumulative market effects β the effectiveness of the price 〖pr〗_i (t) the price at time t for generation i (data exists) α_t the seasonal factor at time t (data exists) g_t the growth rate at time t (data exists) n the number of generations (data exists) l the number of periods (data exists) C_i (t) the capacity restriction regarding the product at time t for generation i (data exists) -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On Sun, 01 May 2011 18:24:30 -0400, Terry Reedy tjre...@udel.edu wrote: : This does not make linear recursion 'bad', just impractical for general : use on finite-memory machines. While I consider it very useful for : learning, it is unnecessary because it is easy to write an iterative : version. So called tail-recursion optimization saves memory by REMOVING : RECURSION and replacing it with iteration. : (...) : Python does not do this automatically because 1) it can be a semantic : change under some circumstances; 2) one who wants the iterative version : can just as easily write it directly; That's the silliest argument I ever heard. The programmer should write the code the way he and application domain experts think, i.e. very often recursively. The compiler should generate code the way the CPU thinks (most optimally), i.e. iteratively. Of course, I am not saying that one should always model problems recursively, and thus also not that one should implement them recursively. Just that when a model is agreed recursively between the stakeholders, one should get a compiler to do the optimisation, not a programmer. I always thought of python as a step forward, in the way it allows direct expression of so many alternative modes of thinking (imperative, functional, recursion, iterators, etc). If what you say is python philosophy, it is a step backward in requiring the programmer to think more about low-level technical matters which even C has managed to leave for the compiler. :and 3) Python has a better way to : process collections that removes essentially all the boilerplate in the : recursive-call and while-loop versions: -- :-- Hans Georg -- http://mail.python.org/mailman/listinfo/python-list
Development software
Hi! I'm new to programming. I started with php earlier and I dropped it for Python. I use Eclipse+PyDev for python, html and css. Which programmes should I start using because they might be useful in the future? Which functions of eclipse are useful but unused/unnoticed by beginners. What do you use and why :) ? -- http://mail.python.org/mailman/listinfo/python-list
Re: Python competitions and learnings
On May 1, 7:22 pm, Alexander Lyabah alexan...@lyabah.com wrote: On May 1, 3:26 am, harrismh777 harrismh...@charter.net wrote: Alexander Lyabah wrote: What do you think about it? I'm also have a not a very good English, so I need help with it too, Alexander, your site is very interesting. I spent some time this afternoon appreciating your work. Nice job. Be encouraged, your English is much better than my Russian! I also looked over the orphanage site and I appreciate how much you are doing there in Ukraine for the children. Keep up the good work. I too am a little disappointed that Python3 is not being used. I want to encourage you to work in that direction as well. I may have some time to volunteer to checkio.org; for help with the English, and maybe with some help as a tester. We'll see... I have a lot of my own fish to fry here, as we say in America. Blessings on your work, friend. m harris I spend a lot of time to make a almost full support of python 2.7 from sandbox. If somebody help me this sandboxed python 3.* i will add support of it on checkio.org with big pleasure. Notice about the python 2.7 on main page was added. thanks for advice -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On Mon, 02 May 2011 10:53:52 +0100, Hans Georg Schaathun wrote: On 02 May 2011 08:56:57 GMT, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: : I see your smiley, but there are a number of similar series as Fibonacci, : with the same recurrence but different starting values, or similar but : slightly different recurrences. E.g. Lucas, primefree, Pell, Padovan and : Perrin numbers. Well, Fibonacci isn't one unique sequence. Any sequence satisfying f(n) = f(n-1) + f(n-2) is /a/ Fibonacci sequence. Regardless of starting values. At least according to some authors. According to the references I have, there is one and only one Fibonacci sequence, the usual one invented by Fibonacci to talk about rabbits. (Actually, we should talk about Fibonacci *numbers*, rather than sequence.) Wolfram Mathworld is typical, defining *the* Fibonacci numbers as those with starting conditions f(1)=1, f(2)=1 (or f(0)=0 if you prefer). http://mathworld.wolfram.com/FibonacciNumber.html The Collins Dictionary of Mathematics agrees with Mathworld. The Lucas numbers (related to, but not the same as, the Lucas sequence) obey the same recurrence as the Fibonacci numbers, but with a different set of starting values. So there is certainly precedent in the mathematical literature for giving different names to the same recurrence with different starting values. In any case, whatever you call them, what I call R(n) is not one, as the recurrence is different: R(n) = R(n-1) + R(n-2) + 1 Penguin, Dict. of Mathematics prefer 1,1,2,3,5 but they also suggest 0,1,1,2,3, ... This depends on whether you start counting from n=0 or n=1. Even the sequence you quote, from Anderson: 1,2,3,5... is just the usual Fibonacci numbers starting at n=2 instead of 1 or 0. (No matter how confusing something is, there's always at least one person who will try to make it *more* confusing.) In short, don't assume that a person talking about Fibonacci numbers assume the same base cases as you do. As far as I'm concerned, there are only two definitions of Fibonacci numbers that have widespread agreement in the mathematical community: 0,1,1,2,3 ... (starting from n=0) 1,1,2,3,5 ... (starting from n=1) Any other definition is rather, shall we say, idiosyncratic. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Python competitions and learnings
On May 2, 1:33 am, Terry Reedy tjre...@udel.edu wrote: On 5/1/2011 12:49 PM, Alexander Lyabah wrote: And what do you think about Score Games and competitions? The rules of the first score game were not clear to me. I could not figure out how to play it interactively myself so I could see how it actually played. -- Terry Jan Reedy I will add a more detail information how competitions and score games goes. -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On Mon, 02 May 2011 14:14:20 +0100, Hans Georg Schaathun wrote: On Sun, 01 May 2011 18:24:30 -0400, Terry Reedy tjre...@udel.edu wrote: : This does not make linear recursion 'bad', just impractical for general : use on finite-memory machines. While I consider it very useful for : learning, it is unnecessary because it is easy to write an iterative : version. So called tail-recursion optimization saves memory by REMOVING : RECURSION and replacing it with iteration. : (...) : Python does not do this automatically because 1) it can be a semantic : change under some circumstances; 2) one who wants the iterative version : can just as easily write it directly; That's the silliest argument I ever heard. You must be new to the Internet then :) The programmer should write the code the way he and application domain experts think, i.e. very often recursively. The compiler should generate code the way the CPU thinks (most optimally), i.e. iteratively. Perhaps so, but there can be a huge gulf between what should happen and what does happen. The CPython implementation is deliberately a naive, not- very clever compiler. (PyPy seems to be the implementation aiming at cutting-edge cleverness.) Even such simple optimizations as constant folding are very controversial among the CPython developers. They have good reasons for their caution: optimizing compilers are renowned for breaking code, especially floating point code, and there have been cases in Python's history where optimizations have broken existing code and needed to be backed out. The problem is, once you include side-effects, recursion and iteration are *not* identical. Specifically, the opposition to tail-recursion optimization in Python is that it plays havoc with the tracebacks you get in the event of an exception. The argument goes: * Debugging is harder than writing code in the first place, so it is more important to simplify debugging, even at the cost of making some code slightly harder to write. * Recursion doesn't just mean simple recursion where a function calls itself, but mutually recursive functions. You could have (say) five functions that mutually called each other recursively, and in the event of a traceback you need to see the exact calling chain, but that's precisely the information that is blown away by tail-recursion optimization. * Tail-recursion is only a special case of recursion, and not a very common special case either, so it is hardly worth the extra complexity of the compiler to treat it specially. Regardless of whether you agree with the arguments or not, they're hardly silly. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
setup.py rebuilds EVERYTHING on windows?
Hi I'm trying to build an extension (spice-0.12) on windows. Whenever I change a single file, everything gets rebuilt. ?? Python2.7.1 Windows XP Visual Studio 9 setuptools 0.6c11 -Mathew -- http://mail.python.org/mailman/listinfo/python-list
Re: Composition instead of inheritance
On 4/28/2011 1:15 PM, Ethan Furman wrote:
For anybody interested in composition instead of multiple inheritance, I
have posted this recipe on ActiveState (for python 2.6/7, not 3.x):
http://code.activestate.com/recipes/577658-composition-of-classes-instead-of-multiple-inherit/
Comments welcome!
~Ethan~
That looks pretty clever. I tried adding this method to Spam:
def test_eggs_02(self):
print('testing eggs_02 from spam')
and it did just what we wanted.
I'm going to have to study this one.
Thanks.
Alan
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Coolest Python recipe of all time
I think it is time to give some visibility to some of the instructive and very cool recipes in ActiveState's python cookbook. My vote for the coolest recipe of all time is: http://code.activestate.com/recipes/365013-linear-equations-solver-in-3-lines/ What are your favorites? Raymond twitter: @raymondh -- http://mail.python.org/mailman/listinfo/python-list
Re: setup.py rebuilds EVERYTHING on windows?
Mathew, 02.05.2011 18:45: I'm trying to build an extension (spice-0.12) on windows. Whenever I change a single file, everything gets rebuilt. Did you report this to the authors? I suppose there's a project mailing list? Stefan -- http://mail.python.org/mailman/listinfo/python-list
Re: Development tools and practices for Pythonistas
Am 02.05.2011 01:33, schrieb David Boddie: After noting the warnings it contains, see the following page for a description of the Python API for Mercurial: http://mercurial.selenic.com/wiki/MercurialApi Ah, yes, no need to use os.sytem(), but all in all not much difference from doing so (and usage of CLI is recommended instead of using the API). I had a look at this page in 2009 and came to the conclusion that it's no good idea to use Mercurial as library. Seems that this still holds true. Git also has a Python API, which is fairly reasonable to use, though a bit different to the Mercurial one: http://www.samba.org/~jelmer/dulwich/ That looks more promising to me. I think I will try this and Bazaar to find which fits my needs better. Regards, Dietmar -- http://mail.python.org/mailman/listinfo/python-list
Re: Running a script with command line arguments
Hi, I'm new to python and trying to run a borrowed script. The error I get suggests that I need to give a proper command to run it. The input file is c26_1plus.csv and the intended output file is c26_1plus_backbone.csv. Can anyone help? The usage string in the script says that the required arguments are: input_file output_file backbone_alpha [file delimiter] You're providing input_file and output_file but not backbone_alpha. -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On 5/2/2011 9:14 AM, Hans Georg Schaathun wrote: On Sun, 01 May 2011 18:24:30 -0400, Terry Reedy : Python does not do this automatically because 1) it can be a semantic : change under some circumstances; 2) one who wants the iterative version : can just as easily write it directly; That's the silliest argument I ever heard. Calling something silly when you have not really read it and perhaps asked questions to really understand it is, to me, silly. If you want a compiler that can introduce bugs into your program by doing what it thinks you meant, rather than what you said, don't use CPython. :and 3) Python has a better way to : process collections that removes essentially all the boilerplate in the : recursive-call and while-loop versions: To properly use modern Python, one should know and use for loops and iterators. -- Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: ctypes and twain_32.dll
Hi! On my system, thera are not twain32.dll or twain_32.dll, but twain.dll @+ -- Michel Claveau -- http://mail.python.org/mailman/listinfo/python-list
raise (type, value, traceback) and raise type, value, traceback
Hi, anyone know why these two statements aren't equivalent? raise (type, value, traceback) raise type, value, traceback -- http://mail.python.org/mailman/listinfo/python-list
Re: raise (type, value, traceback) and raise type, value, traceback
On Mon, May 2, 2011 at 11:23 AM, Jack Bates ms...@freezone.co.uk wrote: Hi, anyone know why these two statements aren't equivalent? raise (type, value, traceback) raise type, value, traceback The latter is the syntax of the raise statement: up to 3 expressions, separated by commas. The former has a single expression that evaluates to a tuple. It's equivalent to this: t = (type, value, traceback) raise t That it accepts the tuple and raises a value-less expression of type `type` surprises me. The docs don't say anything about this, and I would have expected a TypeError, but it appears to be extracting the first element of the tuple and using that as the value of the first expression. -- http://mail.python.org/mailman/listinfo/python-list
Pushing for Pythoncard 1.0
Attempt to push Pythoncard to a 1.0 status is now underway. A temporary website has been created at: http://code.google.com/p/pythoncard-1-0/ The official website continues to be http://pythoncard.sourceforge.net/ Pythoncard is such a wonderful package that it would be a shame to allow development for the package to go stagnant. The Python community deserves to continue enjoying the simplicity of Pythoncard for creating a GUI Python application. In the last few years, I've added a number of widgets and functions to the package. The present effort is to simply incorporate all of the changes I've made to the package, create an installer, push it out the door and announce to the world that Pythoncard 1.0 is here, and is here to stay. Here's a partial list of widgets and functions added: Widgets: PDFWindow, FlashWindow, MatplotlibCanvasWindow, MultiSelectionList, Drag--drop enabled tree control, IEHTMLWindow Backgrounds: MDIParentWindow, MDIChildWindow, MDISashWindow, multi-panel Background Window, Tools: Updated layoutmanager supporting the newly added widgets, and a revived action manager (provide list of actions or events associated with widgets in a context-sensitive fashion - no more needs to memorize which widget can do what). and others. I realize that there are other GUI packages that enjoyed far more support from the Python community in the last few years and have, as a result, a more extensive feature list, and more modern looks. My hats off to those developers. So, please re-frame from responding to this message or send me emails regarding xyz package and how that one is better, more modern than Pythoncard, or that xyz package had xxx feature already. I like Pythoncard because it's so simple for most GUI applications I build that it's almost laughable. I've benefited tremendously from having Pythoncard around and now it's my turn to chip in and repay a small debt to Pythoncard. For x-Pythoncard users (and particularly developers), if you are unable to lend a helping hand, please at least join or re-join the Pythoncard mailing list and let your voice be heard. -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On 02 May 2011 16:41:37 GMT, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: : You must be new to the Internet then :) OK. Maybe I heard something worse last time I was an active news users, years ago. Anyway, most of the silly things I hear do not qualify as arguments :-) : The problem is, once you include side-effects, recursion and iteration : are *not* identical. Specifically, the opposition to tail-recursion : optimization in Python is that it plays havoc with the tracebacks you get : in the event of an exception. The argument goes: Thanks for the comprehensive background. I can see the point that python may be harder to optimise correctly during compilation than many other languages. : Regardless of whether you agree with the arguments or not, they're hardly : silly. I only called one argument silly, namely the one about iterative rewriting being so simple that it is not an issue. Sometimes it isn't, but sometimes it is. The other arguments are valid. And they make me lean more towards more static, compiled languages without the excessive run-time dynamism of python. -- :-- Hans Georg -- http://mail.python.org/mailman/listinfo/python-list
Re: Coolest Python recipe of all time
On Mon, 2 May 2011 10:33:31 -0700 (PDT), Raymond Hettinger pyt...@rcn.com wrote: I think it is time to give some visibility to some of the instructive and very cool recipes in ActiveState's python cookbook. My vote for the coolest recipe of all time is: http://code.activestate.com/recipes/365013-linear-equations-solver-in-3-lines/ Really cool, but wrong. x = 3234.667, not 3236.0 DaveM -- http://mail.python.org/mailman/listinfo/python-list
Re: Coolest Python recipe of all time
On Mon, May 2, 2011 at 2:48 PM, David Monaghan monaghand.da...@gmail.com wrote: On Mon, 2 May 2011 10:33:31 -0700 (PDT), Raymond Hettinger pyt...@rcn.com wrote: I think it is time to give some visibility to some of the instructive and very cool recipes in ActiveState's python cookbook. My vote for the coolest recipe of all time is: http://code.activestate.com/recipes/365013-linear-equations-solver-in-3-lines/ Really cool, but wrong. x = 3234.667, not 3236.0 Nope, I get 3236. Maybe you made a mistake somewhere. -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On May 2, 5:24 pm, Steven D'Aprano steve
+comp.lang.pyt...@pearwood.info wrote:
As far as I'm concerned, there are only two definitions of Fibonacci
numbers that have widespread agreement in the mathematical community:
0,1,1,2,3 ... (starting from n=0)
1,1,2,3,5 ... (starting from n=1)
Any other definition is rather, shall we say, idiosyncratic.
And a concrete reason for preferring the above definition (in either
form) is that divisibility properties of the sequence are much neater
with this choice:
gcd(F_m, F_n) = F_{gcd(m, n)}
--
Mark
--
http://mail.python.org/mailman/listinfo/python-list
Re: Coolest Python recipe of all time
On Mon, 2 May 2011 14:58:50 -0600, Ian Kelly ian.g.ke...@gmail.com wrote: On Mon, May 2, 2011 at 2:48 PM, David Monaghan monaghand.da...@gmail.com wrote: On Mon, 2 May 2011 10:33:31 -0700 (PDT), Raymond Hettinger pyt...@rcn.com wrote: I think it is time to give some visibility to some of the instructive and very cool recipes in ActiveState's python cookbook. My vote for the coolest recipe of all time is: http://code.activestate.com/recipes/365013-linear-equations-solver-in-3-lines/ Really cool, but wrong. x = 3234.667, not 3236.0 Nope, I get 3236. Maybe you made a mistake somewhere. Oops. What a plonker .Three times I checked and got the same result each time. Now it works fine. Sorry! DaveM -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
Thomas Rachel wrote: ... because each recursion level 'return' calls fib() twice, and each of those calls fib() twice, and you get the point... yes - but they are called one after the other, so the twice call counts only for execution speed, not for recursion depth. def fib(n): if n == 1: return(n) else: return (fib(n-1)+fib(n-2)) They *are not* called one after the other in the sense that there is ever only one level of recursion with each call (not at all). Take a closer look. Each call to fib() forces a double head, and each of those forces another double head (now four), and so on... the recursion depth exception of the OP testifies against your theory. The thing about this problem that puzzles me, is why we might consider recursion for a possible solution in the first place. In other words, normally we consider using recursion when we need information further down the stack then we have now... so that recursion is necessary because each head call will not have the information it needs for completion until the tail clean-up (coming back up the stack) provides that information. In the case of the fib() numbers (or the fib sequence) recursion is not necessary for correctly handling of the problem. The simple straight-forward obvious way to handle the problem is to calculate the sequence outright in a straight-forward way. On the other hand, Otten's use of yield (making a generator) makes some sense too, in the case that we want to get the fib numbers over time without taking the time to calculate the entire sequence up-front. Just saying... kind regards, m harris -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On Mon, May 2, 2011 at 11:14 PM, Hans Georg Schaathun h...@schaathun.net wrote: That's the silliest argument I ever heard. The programmer should write the code the way he and application domain experts think, i.e. very often recursively. The compiler should generate code the way the CPU thinks (most optimally), i.e. iteratively. The CPU can function iteratively or recursively. The main difference between the programmer and the CPU there is that the CPU is always imperative, while a programmer might want to think functionally, or in an event-driven model, and then under the covers the compiler translates that into imperative code. But in my opinion, the programmer and the interpreter/compiler are teammates. If you allow programmers to be stupid, you will get a lot of stupid programmers writing code. (I think that's one of PHP's biggest downsides.) If the human and the machine know each other well enough, the resulting code can be orders of magnitude more efficient to run, *without taking any more tme to code* because the programmer already knew the right things to do. Perhaps it will take you four hours to read through something, study it, maybe eyeball the compiler's source code, maybe do some disassembly. If you have a few years of career ahead of you, you'll benefit many times over from those few hours, and without spending extra time, you'll produce better code. THAT is what distinguishes the master from the novice. Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
(beginner question) ConfigParser nuances
Hi - Beginner question here. I'm working with ConfigParser. I'd like to take a multiline variable and convert it directly to an array. Seems like a common problem, but I don't see how I can do it without doing a little parsing in my own code. Here's what I'm doing ... import ConfigParser import io sample = ... [Example] ... fruit = apple ... orange ... pear ... config = ConfigParser.RawConfigParser() config.readfp(io.BytesIO(sample)) config.get(Example, fruit) 'apple\norange\npear' temp = config.get(Example, fruit) temp.split() ['apple', 'orange', 'pear'] I'm thinking there's a way to avoid this intermediate temp.split() step. Is there not a way to move a multiline value straight into an array using ConfigParser? Thanks for the help. -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On Tue, May 3, 2011 at 7:50 AM, harrismh777 harrismh...@charter.net wrote: They *are not* called one after the other in the sense that there is ever only one level of recursion with each call (not at all). Take a closer look. Each call to fib() forces a double head, and each of those forces another double head (now four), and so on... the recursion depth exception of the OP testifies against your theory. def fib(n): if n==1: return n return fib(n-1)+fib(n-2) dis.dis(fib) 2 0 LOAD_FAST0 (n) 3 LOAD_CONST 1 (1) 6 COMPARE_OP 2 (==) 9 JUMP_IF_FALSE5 (to 17) 12 POP_TOP 3 13 LOAD_FAST0 (n) 16 RETURN_VALUE 17 POP_TOP 4 18 LOAD_GLOBAL 0 (fib) 21 LOAD_FAST0 (n) 24 LOAD_CONST 1 (1) 27 BINARY_SUBTRACT 28 CALL_FUNCTION1 31 LOAD_GLOBAL 0 (fib) 34 LOAD_FAST0 (n) 37 LOAD_CONST 2 (2) 40 BINARY_SUBTRACT 41 CALL_FUNCTION1 44 BINARY_ADD 45 RETURN_VALUE The recursion is in the last block. Note that it calls a function, then keeps going. It doesn't fork. There are two CALL_FUNCTION opcodes, called *sequentially*. In terms of the call stack, there is only ever one of those two calls active at any given time. Also, as earlier pointed out, the reason for the stack overflow is that fib(2) will call fib(1) and fib(0), and fib(0) will call fib(-1) and fib(-2), etc. Changing the operator from == to = in the conditional return will solve this. Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
Re: (beginner question) ConfigParser nuances
On Mon, May 2, 2011 at 3:04 PM, Unknown Moss unknownm...@gmail.com wrote: Hi - Beginner question here. I'm working with ConfigParser. I'd like to take a multiline variable and convert it directly to an array. Seems like a common problem, but I don't see how I can do it without doing a little parsing in my own code. Here's what I'm doing ... import ConfigParser import io sample = ... [Example] ... fruit = apple ... orange ... pear ... config = ConfigParser.RawConfigParser() config.readfp(io.BytesIO(sample)) config.get(Example, fruit) 'apple\norange\npear' temp = config.get(Example, fruit) temp.split() ['apple', 'orange', 'pear'] I'm thinking there's a way to avoid this intermediate temp.split() step. Is there not a way to move a multiline value straight into an array using ConfigParser? Nope, there is not. I think some might instead use several numbered options to similar effect: # config file [Example] fruit1: apple fruit2: orange fruit3: pear # Python from itertools import count fruits = [] names = (fruit + str(i) for i in count(1)) for name in names: if not config.has_option(Example, name): break fruits.append(config.get(Example, name)) Cheers, Chris -- http://rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On Mon, May 2, 2011 at 3:50 PM, harrismh777 harrismh...@charter.net wrote: Thomas Rachel wrote: ... because each recursion level 'return' calls fib() twice, and each of those calls fib() twice, and you get the point... yes - but they are called one after the other, so the twice call counts only for execution speed, not for recursion depth. def fib(n): if n == 1: return(n) else: return (fib(n-1)+fib(n-2)) They *are not* called one after the other in the sense that there is ever only one level of recursion with each call (not at all). Take a closer look. Each call to fib() forces a double head, and each of those forces another double head (now four), and so on... The branching factor has nothing to do with the maximum stack depth. If you don't believe me, consider this little script: import inspect def maxstack(n): if n = 0: return len(inspect.stack()) else: return max(maxstack(n-1), maxstack(n-2)) print maxstack(15) This prints 17. Now consider this script, which is similar but singly-recursive: import inspect def maxstack(n): if n = 0: return len(inspect.stack()) else: return maxstack(n-1) print maxstack(15) This also prints 17. Note: they're the same. the recursion depth exception of the OP testifies against your theory. The OP's recursion depth exception was because a malformed base case made the recursion infinite. It had nothing to do with the branching factor. -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On Tue, May 3, 2011 at 8:22 AM, Ian Kelly ian.g.ke...@gmail.com wrote: They *are not* called one after the other in the sense that there is ever only one level of recursion with each call (not at all). Take a closer look. Each call to fib() forces a double head, and each of those forces another double head (now four), and so on... The branching factor has nothing to do with the maximum stack depth. Side point: In a massively parallel environment, branching like this COULD be implemented as a fork. I just don't know of any implementations of Python that do so. (And of course, it works for fib() because it needs/uses no global state, which makes the recursions completely independent. Not all functions are so courteous, and the compiler can't necessarily know the difference.) Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
Re: Development software
On Tue, May 3, 2011 at 1:23 AM, Petey efri...@gmail.com wrote: Which programmes should I start using because they might be useful in the future? Which functions of eclipse are useful but unused/unnoticed by beginners. What do you use and why :) ? You're going to get some extremely disparate responses to that! I'll open with the disclaimer that will apply to everyone's posts: This is personal opinion, not Gospel truth. :) For my development (which is quite polyglot - at the moment, C++/Python/PHP/makefile/Pike/text all up in tabs), I use SciTE and a good makefile. I hit F7 and Scite runs make in the current file's directory. Is it an IDE or an editor? I'm not really sure; it's an editor that lets me scroll through compiler errors with F4/Shift-F4. A well-made makefile is an awesome tool. I strongly recommend getting familiar with your make utility (if you don't currently have one, get GNU make). My make will build either the production or debug version of my code, upload changed files to our deployment server, and in fact do everything except push changes into our git repo (I prefer to do that manually, as I usually want to build lots of times and only then commit the change in git). Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On Mon, 02 May 2011 21:02:43 +0100, Hans Georg Schaathun wrote: The other arguments are valid. And they make me lean more towards more static, compiled languages without the excessive run-time dynamism of python. If you value runtime efficiency over development time, sure. There are plenty of languages which have made that decision: Pascal, C, Java, Lisp, Forth, and many more. Python aims at acceptable performance (between 10 and 100 times slower than C) and much easier development (between 10 and 100 times faster than C *wink*). If that tradeoff doesn't suit you, perhaps Python is not the language for you. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Py / VNC Automation
Hi, I'm looking for a python class or open source code that is tightly integrated with VNC protocols - any ideas? -- http://mail.python.org/mailman/listinfo/python-list
Re: Py / VNC Automation
On Tue, May 3, 2011 at 10:23 AM, PyNewbie ryan.morr...@gmail.com wrote:
Hi,
I'm looking for a python class or open source code that is tightly integrated
with VNC protocols - any ideas?
It's not a complex protocol; you could fairly readily work it
manually. The protocol itself is called RFB - see
http://en.wikipedia.org/wiki/RFB_protocol which has links to the
official protocol spec. Working it from Python is as simple as
creating a socket (import socket; vnc=socket.socket();
vnc.connect(('address',5900))) and sending and receiving binary data.
If you're setting things up as a test, I recommend playing around with
authentication disabled - it's a lot easier to master the protocol in
its simplest form.
Chris Angelico
--
http://mail.python.org/mailman/listinfo/python-list
Re: Py / VNC Automation
On Mon, May 2, 2011 at 5:23 PM, PyNewbie ryan.morr...@gmail.com wrote: Hi, I'm looking for a python class or open source code that is tightly integrated with VNC protocols - any ideas? -- http://mail.python.org/mailman/listinfo/python-list I've not updated this in a while, but it's got a python vnc viewer in the list: http://stromberg.dnsalias.org/~dstromberg/vnc.html -- http://mail.python.org/mailman/listinfo/python-list
Recursion or iteration (was Fibonacci series recursion error)
On May 3, 2:50 am, harrismh777 harrismh...@charter.net wrote: The thing about this problem that puzzles me, is why we might consider recursion for a possible solution in the first place This can be answered directly but a bit lengthily. Instead let me ask a seemingly unrelated (but actually much the same) question. Here are two power functions: def powI(x,n): result = 1 for i in range(0,n): result = result * x return result def powR(x,n): return 1 if (n==0) else (x * powR(x, n-1)) What are their space/time complexities? Which do you prefer? -- http://mail.python.org/mailman/listinfo/python-list
Re: Development software
On May 2, 8:23 pm, Petey efri...@gmail.com wrote: Hi! I'm new to programming. I started with php earlier and I dropped it for Python. I use Eclipse+PyDev for python, html and css. Which programmes should I start using because they might be useful in the future? Which functions of eclipse are useful but unused/unnoticed by beginners. What do you use and why :) ? Chris talked of a good make tool. Yes this is necessary for more 'in- the-large' programming. But for a beginner its very important to have tight development cycle -- viz. a. Write a function b. Check the function c. Change the definition d. Check that etc with a minimum of keystrokes If eclipse gives that its good... For me its emacs with python-mode: python in one window python file in other jump between the two with one keystroke. Ive heard very good things about ipython (especially for introspection) but not tried it extensively myself -- http://mail.python.org/mailman/listinfo/python-list
Re: Recursion or iteration (was Fibonacci series recursion error)
On Tue, May 3, 2011 at 11:48 AM, rusi rustompm...@gmail.com wrote: What are their space/time complexities? Which do you prefer? They're pretty similar actually. If you rework the first one to not use range() but instead have a more classic C style of loop, they'll be almost identical: def powI(x,n): result = 1 while n 0: result *= x n-=1 return result There's a subtle difference in that powR as you've coded it will infinite-loop if given a negative exponent, while powI in any form will simply return 1 (neither is technically correct, fwiw). Other than that, the only difference is that one keeps its state on the call stack, the other uses a temporary variable. Performance would probably benefit from a special syntax meaning recurse, which would avoid the LOAD_GLOBAL for the function's name (plus, things break if you pass recursive functions around after compiling them - for instance, powR2=powR; def powR(x,n): os.exit() - but if you do that, then you should expect to see nice bullet-holes in your foot). However, I do not believe that Python would overall benefit from any such thing. Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
Re: Development software
On Tue, May 3, 2011 at 12:04 PM, rusi rustompm...@gmail.com wrote: Chris talked of a good make tool. Yes this is necessary for more 'in- the-large' programming. But for a beginner its very important to have tight development cycle -- viz. a. Write a function b. Check the function c. Change the definition d. Check that etc with a minimum of keystrokes a. Write a code file b. Press F7 and see the output in the other window. c, d. Iterate. Most IDEs will give you some such facility. F7 happens to be SciTE's keystroke, others may use Ctrl-F9 or F5 or C-x M-x butterfly, but it's almost certainly going to be there. Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
complex data structures in python
Hello, I was wondering if anyone has any documentation/recipes for implementing complex data structures. For instance, if you had a dictionary with a list inside a list inside a set. -- --- Get your facts first, then you can distort them as you please.-- -- http://mail.python.org/mailman/listinfo/python-list
Re: (beginner question) ConfigParser nuances
On May 2, 3:25 pm, Chris Rebert c...@rebertia.com wrote: On Mon, May 2, 2011 at 3:04 PM, Unknown Moss unknownm...@gmail.com wrote: Hi -Beginnerquestionhere. I'm working with ConfigParser. I'd like to take a multiline variable and convert it directly to an array. Seems like a common problem, but I don't see how I can do it without doing a little parsing in my own code. Here's what I'm doing ... import ConfigParser import io sample = ... [Example] ... fruit = apple ... orange ... pear ... config = ConfigParser.RawConfigParser() config.readfp(io.BytesIO(sample)) config.get(Example, fruit) 'apple\norange\npear' temp = config.get(Example, fruit) temp.split() ['apple', 'orange', 'pear'] I'm thinking there's a way to avoid this intermediate temp.split() step. Is there not a way to move a multiline value straight into an array using ConfigParser? Nope, there is not. I think some might instead use several numbered options to similar effect: # config file [Example] fruit1: apple fruit2: orange fruit3: pear # Python from itertools import count fruits = [] names = (fruit + str(i) for i in count(1)) for name in names: if not config.has_option(Example, name): break fruits.append(config.get(Example, name)) Cheers, Chris --http://rebertia.com Ok, thanks Chris. Maybe I'm getting too lazy in my old age. :-) -- http://mail.python.org/mailman/listinfo/python-list
Re: Fibonacci series recursion error
On May 3, 5:21 am, Steven D'Aprano steve +comp.lang.pyt...@pearwood.info wrote: On Mon, 02 May 2011 21:02:43 +0100, Hans Georg Schaathun wrote: The other arguments are valid. And they make me lean more towards more static, compiled languages without the excessive run-time dynamism of python. If you value runtime efficiency over development time, sure. There are plenty of languages which have made that decision: Pascal, C, Java, Lisp, Forth, and many more. Or Haskell: Succinctness like python Type safety better than C, C++, Java with a minimum of type declarations -- http://mail.python.org/mailman/listinfo/python-list
Re: complex data structures in python
On Mon, May 2, 2011 at 7:46 PM, Rita rmorgan...@gmail.com wrote: Hello, I was wondering if anyone has any documentation/recipes for implementing complex data structures. For instance, if you had a dictionary with a list inside a list inside a set. Er, there's no special magic. The datatypes just nest normally. Pretty much the only thing to look out for is immutability/hashability. Dictionary keys and set elements should typically be immutable (and thus sensibly hashable). For this reason, tuples and frozensets are used instead of lists and non-frozen sets (respectively) in those situations (and in other cases where mutability should be disallowed). When creating a custom immutable type, one should override the __eq__(), __ne__(), and __hash__() special methods so that the type's instances can be used as dict keys and set elements. Your particular example combination doesn't work since it violates the aforementioned immutability rule. One should also be aware of the datatypes in the `collections` module, particularly `defaultdict`: http://docs.python.org/library/collections.html Cheers, Chris -- http://rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Coolest Python recipe of all time
David Monaghan, 02.05.2011 23:45: On Mon, 2 May 2011 14:58:50 -0600, Ian Kelly wrote: On Mon, May 2, 2011 at 2:48 PM, David Monaghan wrote: On Mon, 2 May 2011 10:33:31 -0700 (PDT), Raymond Hettinger wrote: I think it is time to give some visibility to some of the instructive and very cool recipes in ActiveState's python cookbook. My vote for the coolest recipe of all time is: http://code.activestate.com/recipes/365013-linear-equations-solver-in-3-lines/ Really cool, but wrong. x = 3234.667, not 3236.0 Nope, I get 3236. Maybe you made a mistake somewhere. Oops. What a plonker .Three times I checked and got the same result each time. Now it works fine. Sorry! The bad thing about this recipe is that it requires quite a bit of background knowledge in order to infer that the code the developer is looking at is actually correct. At first sight, it looks like an evil hack, and the lack of documentation doesn't help either. Stefan -- http://mail.python.org/mailman/listinfo/python-list
Re: Coolest Python recipe of all time
On Mon, May 2, 2011 at 11:04 PM, Stefan Behnel stefan...@behnel.de wrote: The bad thing about this recipe is that it requires quite a bit of background knowledge in order to infer that the code the developer is looking at is actually correct. At first sight, it looks like an evil hack, and the lack of documentation doesn't help either. What do you mean, looks like? For crying out loud, it abuses complex numbers to represent 2-element vectors, and it passes unvalidated input to eval(). It is *absolutely* an evil hack! Albeit a clever one... -- http://mail.python.org/mailman/listinfo/python-list
Re: Recursion or iteration (was Fibonacci series recursion error)
On Mon, May 2, 2011 at 7:13 PM, Chris Angelico ros...@gmail.com wrote: On Tue, May 3, 2011 at 11:48 AM, rusi rustompm...@gmail.com wrote: What are their space/time complexities? Which do you prefer? They're pretty similar actually. If you rework the first one to not use range() but instead have a more classic C style of loop, they'll be almost identical: def powI(x,n): result = 1 while n 0: result *= x n-=1 return result There's a subtle difference in that powR as you've coded it will infinite-loop if given a negative exponent, while powI in any form will simply return 1 (neither is technically correct, fwiw). Other than that, the only difference is that one keeps its state on the call stack, the other uses a temporary variable. The recursive solution uses more stack. That is true. But the recursive solution has time complexity of O(logn). The iterative solution has time complexity of O(n). That's a significant difference for large n - a significant benefit of the recursive version. However, an iterative version of a function can always be created from a recursive version. In this case, an iterative version can be constructed that is O(logn) time and O(1) stack. -- http://mail.python.org/mailman/listinfo/python-list
Re: Recursion or iteration (was Fibonacci series recursion error)
On Tue, May 3, 2011 at 3:27 PM, Dan Stromberg drsali...@gmail.com wrote: But the recursive solution has time complexity of O(logn). The iterative solution has time complexity of O(n). That's a significant difference for large n - a significant benefit of the recursive version. Are you sure? It will produce n function calls and n multiplications, how is that O(log n)? Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
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Re: Recursion or iteration (was Fibonacci series recursion error)
On Mon, May 2, 2011 at 11:27 PM, Dan Stromberg drsali...@gmail.com wrote: But the recursive solution has time complexity of O(logn). The iterative solution has time complexity of O(n). That's a significant difference for large n - a significant benefit of the recursive version. It's linear as written. I think you're talking about an implementation like this one: def powR(x,n): if n 0: return 1.0 / powR(x, -n) elif n == 0: return 1 else: half_n = n // 2 root = powR(x, half_n) result = root * root if half_n + half_n == n - 1: result = result * x return result That's O(log n), but it was harder to write, and it could just as easily be iterative. In fact it might actually have been a bit simpler to write it iteratively. -- http://mail.python.org/mailman/listinfo/python-list
Re: Recursion or iteration (was Fibonacci series recursion error)
On Mon, May 2, 2011 at 10:29 PM, Chris Angelico ros...@gmail.com wrote: On Tue, May 3, 2011 at 3:27 PM, Dan Stromberg drsali...@gmail.com wrote: But the recursive solution has time complexity of O(logn). The iterative solution has time complexity of O(n). That's a significant difference for large n - a significant benefit of the recursive version. Are you sure? It will produce n function calls and n multiplications, how is that O(log n)? Doh. Usually when someone gives a recursive solution to this problem, it's O(logn), but not this time. Here's a logn one: def power(x, n): if n == 0: return 1 else: half, remainder = divmod(n, 2) if remainder == 1: return power(x, half) ** 2 * x else: return power(x, half) ** 2 -- http://mail.python.org/mailman/listinfo/python-list
[issue11975] Fix intersphinx-ing of built-in types (list, int, ...)
Ezio Melotti ezio.melo...@gmail.com added the comment: See also #4966 and #11976. -- nosy: +ezio.melotti ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11975 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4966] Improving Lib Doc Sequence Types Section
Ezio Melotti ezio.melo...@gmail.com added the comment: See also #11975 and #11976. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4966 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11967] Left shift and Right shift for floats
Martin v. Löwis mar...@v.loewis.de added the comment: Ok, I'm closing this as won't fix. Mark is our authority on these matters, and having two spellings for this fairly uncommon operation seems enough. -- resolution: - wont fix status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11967 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11887] unittest fails on comparing str with bytes if python has the -bb option
STINNER Victor victor.stin...@haypocalc.com added the comment: Le lundi 02 mai 2011 07:05:28, vous avez écrit : * the patch introduces code/complexity in _baseAssertEqual and other places, using catch_warnings to change and restore the warning filters at every call; Yes, and what is the problem? I think that it is cheap: it copies a list, prepends an item to a short list, and then copies a reference (the previous list). I think that the patch is simple (it adds 3 with+simplefilter) and it doesn't add complexity, or you should define what complexity is :-) * this is needed only when Python is run with -b/-bb and that is quite uncommon (afaik); Buildbots use make buildbottest which run python with -bb (which is a good idea!). So all buildbots already use -bb since long time. I forgot the explain the usecase: I don't remember correctly, but a test failed on a buildbot, and I was unable to get more information because unittest failed too. * even if this is not fixed, a test suite that passes all the tests without -b/-bb will most likely pass with -b/-bb[0]; No. You have usually more failures with -bb than without any -b flag. Not in the test itself, but in a function called by the test. * if there are failing tests with -b/-bb, it's usually possible to remove the -b/-bb and fix them before re-adding -bb[1]; A test may only fail with -bb. Anyway, my problem is to be able to get more informations on a failure in a buildbot. I cannot change (easily) -bb flags on the buildbots (and I don't want to do that). When something goes wrong on a buildbot, in some cases it is very hard to reproduce the failure on my own computer. I want as much information as possible. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11887 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11839] argparse: unexpected behavior of default for FileType('w')
Stefan Pfeiffer stefan.pfeif...@gmail.com added the comment: Happens in 3.2, too... Would be nice to see that fixed. Stefan -- nosy: +Stefan.Pfeiffer ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11839 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11975] Fix referencing of built-in types (list, int, ...)
Éric Araujo mer...@netwok.org added the comment: I changed the title: intersphinx is a Sphinx extension used to links to foreign documentation, not create links inside one doc (as I understand the request is). -- nosy: +eric.araujo stage: - needs patch title: Fix intersphinx-ing of built-in types (list, int, ...) - Fix referencing of built-in types (list, int, ...) versions: +Python 2.7, Python 3.1, Python 3.2, Python 3.3 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11975 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11935] MMDF/MBOX mailbox need utime
Steffen Daode Nurpmeso sdao...@googlemail.com added the comment: On Sun, 1 May 2011 00:15:11 +0200, R. David Murray rep...@bugs.python.org wrote: The problem with this patch is that it would also show 'new mail' if what had in fact happened was that a message had been *deleted* (see the comments at the beginning of the flush method). So actually fixing this is a bit more complicated. Well i don't think so because MUA's do some further checks, like checking the size and of course the status of each mail; some indeed use the mtime as an entry-gate for further inspection. And deleting an entry should surely pass that gate, too. Please do see the file mbox.c of the mutt(1) source repository, which in fact seems to have been used as an almost copy-and-paste template for the implementation of large parts of mailbox.py. But note that i just search less than five minutes in mailbox.py to find a place where i can add the code of the patch (after i've added an identical workaround for my S-Postman), so of course it may not catch all cases. One error is obvious: it also sets the mtime for that Babylon format. I don't use emacs and i'm a buddhist so i don't care about that Babylon mess anyway. Right? A proper fix for this should also consider fixing issue 7359. Hm. #7359 refers to misconfiguration, not to Python or mailbox.py. Maybe Doc/library/mailbox.rst should be adjusted to give users which are new to UNIX a hint about ,group mail` and the set-group-ID on directories? I think this would really be a good thing?!?! Should i open an issue on that? But again, mailbox.py reflects almost one-to-one (except for the naive file lock handling in comparison and AFAIK) mutt(1)'s mbox.c, and i think that if mutt(1) does create-temp-work-work-work-rename then this should be ok for mailbox.py, too. Did you know that ,bin Laden` ment ,am loading` in german? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11935 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11935] MMDF/MBOX mailbox need utime
Steffen Daode Nurpmeso sdao...@googlemail.com added the comment: I'll attach a patch with a clearer comment (entry-gate instead new mail), i.e. the comment now reflects what MUAs really do. -- Added file: http://bugs.python.org/file21850/11935.2.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11935 ___diff --git a/Lib/mailbox.py b/Lib/mailbox.py --- a/Lib/mailbox.py +++ b/Lib/mailbox.py @@ -692,6 +692,13 @@ self._file = open(self._path, 'rb+') self._toc = new_toc self._pending = False +# Set modification time to be after access time so that MMDF and MBOX +# mail readers detect changes (or perform further inspection to do so) +try: +currtime = time.time() +os.utime(self._path, (currtime-3, currtime)) +except: +pass if self._locked: _lock_file(self._file, dotlock=False) ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11935] MMDF/MBOX mailbox need utime
Changes by Steffen Daode Nurpmeso sdao...@googlemail.com: Removed file: http://bugs.python.org/file21795/mailbox.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11935 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11975] Fix referencing of built-in types (list, int, ...)
Jonas H. jo...@lophus.org added the comment: Actually I need to be able to intersphinx (because my documentation work is not the Python docs :-) but I guess it boils down to the same problem of incomplete Sphinx module/class indices. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11975 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue10252] Fix resource warnings in distutils
Roundup Robot devnull@devnull added the comment: New changeset c02c78d93a2e by Éric Araujo in branch '2.7': Fix double use of f.close(). http://hg.python.org/cpython/rev/c02c78d93a2e -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue10252 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8498] Cannot use backlog = 0 for sockets
Daniel Evers derm...@googlemail.com added the comment: To revive this issue, I tried to write a unit test to verify the behaviour. Onfurtunately, the test doesn't work and I don't understand why. I hope, someone here is more enlightend than me... (files: server.py, client.py) -- Added file: http://bugs.python.org/file21851/server.py ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8498 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8498] Cannot use backlog = 0 for sockets
Daniel Evers derm...@googlemail.com added the comment: (client.py) -- Added file: http://bugs.python.org/file21852/client.py ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8498 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
