Mailman 3 January 2012 - Python-ideas

Pythonic buffering in Py3 print()
by anatoly techtonik Jan. 11, 2012

Jan. 11, 2012

In Python 2 "print 'something', statement calls were unbuffered and immediately appeared on screen. In Python 3 "print('something', end='')" calls are buffered. This breaks progress bars and other stuff. 1. What is more "Pythonic" and why? 2. Should Python 3 be fixed ASAP? -- anatoly t.

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Boolean value of file object?
by Mike Meyer Jan. 9, 2012

Jan. 9, 2012

Just an off-the-wall thought. Is there any reason a file object's boolean value shouldn't be false once it's been closed? This would allow replacing "if f and f.closed:" (to make sure you have a file and it's open) with just "if f:". Is there some use case where you want to verify that an object is a file object instead of None (or another false value), and don't care if it's closed? My own thought is that this is a case where status quo wins, but thought someone else might think the idea has … [View More]

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adding a casefold() method to str
by Benjamin Peterson Jan. 8, 2012

Jan. 8, 2012

Hi, Casefolding (Unicode Standard 3.13) is a more aggressive version of lowercasing. It's purpose to assist in the implementation of caseless mapping. For example, under lowercase "ß" -> "ß" but under casefolding "ß" -> "ss". I propose we add a casefold() method. So, case-insensitive matching should really be "one.casefold() == two.casefold()" rather than "one.lower() == two.lower()". Regards, Benjamin

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Sampling Profiler for Python
by Torsten Landschoff Jan. 7, 2012

Jan. 7, 2012

Hello world, since I moved from Java development to Python development, I really miss the sampling profiler of jvisualvm (http://visualvm.java.net/). Perhaps it is only me but especially for long running GUI applications, I would really like to know why it sometimes slows down to a crawl. cProfile is not really useful for this as it makes the software unresponsive alone. Also if using multiple threads (like doing some I/O in background, when using http://www.lag.net/paramiko/) it will … [View More]give meaningless results. I looked for an existing profiler and found statprof, mentioned in this blog: http://wingolog.org/archives/2005/10/28/profiling However, this still fails profiling multiple threads. I don't think one can do any better without touching the interpreter core. So that's what I tried... My approach implements the profiler from the following parts: 1. Sample Trigger: A timer that triggers taking samples of all threads at fixed intervals. 2. Sampling function injection: Ensures that a sampling function is called on each thread at the first opportunity after the sample trigger fired. 3. Sampling function: A function that assigns the current time slice to the executing code on the thread it is called on. Only the second part has to be implemented in the Python interpreter core, the sample trigger and sampling functions can be provided by external modules. My implementation of (2) can be found at https://bitbucket.org/bluehorn/sampling_prof I also prepared a first implementation of (1) and (3) at https://bitbucket.org/bluehorn/profiler_util. Using that library, I can profile pybench with a 3 % slowdown (taking 100 profiling samples per second): $ export PYTHON_PATH=$HOME/python-work/profiler_util $ python3 -m sampling_profiler -- Tools/pybench/pybench.py -c stock.pybench -f prof.pybench [...] Totals: 3119ms 3072ms +1.5% 3198ms 3108ms +2.9% This also shows that the string benchmark takes the most time: Thread MainThread (3842 samples, 38.434401 seconds) ------------------------------------------------------------------------ cpu_time (cum) ticks (cum) samples (cum) filename:lineno function 0.548 0.548 55 55 55 55 Tools/pybench/Strings.py:455 test 0.448 0.448 45 45 45 45 Tools/pybench/Strings.py:568 calibrate 0.428 0.428 43 43 43 43 Tools/pybench/Constructs.py:484 test 0.380 0.380 38 38 38 38 Tools/pybench/Calls.py:445 f 0.324 0.324 34 34 34 34 Tools/pybench/Calls.py:122 f The output is explained as follows: cpu_time: cpu time in seconds accounted to that line. (cum): This is the cpu time including the cumulative time of the functions called on that line. Gathering that data means that the sampling function has to walk the stack for each sample, which will cause a dramatic slowdown for deeply recursive calls. There should be a switch to disable this. ticks: Number of sampling profiler ticks accounted to that line. For my example (where sample ticks are equidistant in wall time) this is a measure of the time spent in that line, including any blocking calls (especially I/O). (cum): ... including called functions samples: Number of times the sampling profiler function was called for that line. This should equal ticks unless execution of that line took longer than a profiler tick. The remaining output should be obvious. I have to admit that this is far from finished, but I hope to get some feedback and perhaps even help by posting it here. What do you think? Greetings, Torsten [View Less]

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Idea: Google Groups web interface for Ideas
by anatoly techtonik Jan. 4, 2012

Jan. 4, 2012

As you may know, the python-ideas list is opened only to subscribers. This is inconvenient, because: 1. it requires three step subscription process 2. it is impossible to post a reply to existing thread/idea There is a web-interface in Google Groups at https://groups.google.com/forum/#!forum/python-ideas that can solve problems above and provide some more nifty features such as embedded search. But there comes another problem that messages posted through the group doesn't end in list, … [View More]

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Proposed PEP on concurrent programming support
by Jim Jewett Jan. 4, 2012

Jan. 4, 2012

(I've added back python-ideas, because I think that is still the appropriate forum.) >.... A new > suite type - the ``transaction`` will be added to the language. The > suite will have the semantics discussed above: modifying an object in > the suite will trigger creation of a thread-local shallow copy to be > used in the Transaction. Further modifications of the original will > cause all existing copies to be discarded and the transaction to be > restarted. ... How will … [View More]

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working on a PEP for the __preview__ package
by Eli Bendersky Jan. 4, 2012

Jan. 4, 2012

Hello, I plan to take the ideas discussed in the thread on the __experimental__/__preview__ package (1), and further elaborated by Nick Coghlan in (2), and turn it into a PEP. Further, I'm willing to invest the time resources to make the package release-worthy before Alpha 1 of 3.3, with at least one module in it. This work will be done under the mentorship of Nick Coghlan. Any ideas, suggestions or objections are welcome. Eli ---- (1) http://mail.python.org/pipermail/python-ideas/2011-… [View More]

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Re: [Python-ideas] [Python-Dev] hello, new dict addition for new eve ?
by julien tayon Jan. 4, 2012

Jan. 4, 2012

Hello, I had tough time finding a connection to internet :) @Arnaud + Terry Thx, code corrected to have the right terminology. at least my code really test for the good rules :) But being precise matter, so that I changed all the terms to fit in. @nathan << is a symbol indicating an asymetry for left and right value, and I carefully tried to have a symetrical behaviour with left & right : associativity, distribution, commutativity. The whole point about using a symbol, is that it … [View More]follow rules. That is the reason why consistent_addition class is all about testing linear algebraic rules (hopefully the right way, and now, I hope with the right terminology). But I have reason to think that there are more than way to do addition. Linear algebrae is the most used and intuitive one for non developer, and developer think of sets operations as more intuitive. I guess, it all come down to one point. Which is what is a dict as a mathematical object. If there is more than one choice, which has the most benefits. Should there be more than one definition ? @Guido & Eric In my book there are rules for sets. The question is a dict the same as a vector or as a set ? since sets are using logical operators for operations that are roughly sets operations why not use & ^ | for sets operation on dict ? it would be pretty consistent with sets operations. ( @jakkob ) In this case I would expect inconsistencies error when doing dict( a = 1 ) | dict( a = 2 , b = 2 ) (thus key-> value are seen like an atomic element of the set, unless a "value collision" operator is given, and this collision operator would recursively and naturely apply to the descendants) because I expect both a | b == b | a and a + b = b + a The problem would be indeed list + list vectorish behaviour is my prefered of course. but if we shift the record algebrae addition to another symbol (let's assume << ) we resolve the conflict. But then we have a problem of retro compatibility. We then may be tempted to use & | ^ (since it would be used for dict) and then we have a problem : should [ 1 , 2 ] & [ 3 , 2 ] mean set addition or applying & to all the element of the same rank ? I'm pretty stucked myself in trying to be consistent. Just for the record, why dit you not use "." (dot) for concatenation ? I know it is typographically unreadable on a messy screen, but is there a better reason ? @terry & Nathan Regarding Counter. on https://github.com/jul/ADictAdd_iction/blob/master/demonstrate.py#L120 you may notice that I do have all the property of counter, but counter does not as -this dict- aggregate values and (sub) totals at the same time. It is very convenient for map reduce since it does some re-reduce operations at reduce time. smart, no ? <:o) @terry Sorry for making assertive and carefree statements regarding strong resentment. My bad. @bruce, truth is aim at similarity cosinus for dict, and I imagine a map reduce on dict representing values of a model you want ideal = dict( blue = 1 , height = 180, weight = 70, wage = 500 ) in the filter before the map reduce you would want to filter all records close to this one by using similarity cosinus in this way : filter( lambda model : cos( ideal, model) > .7 , all_model ) http://en.wikipedia.org/wiki/Cosine_similarity of course I will try to advocate dot product, and metrics. As a result my real goal is to make people consider dict as vectors of path to value => value not sets of key => value To solve issues such as weighted decisions and non linear choices (based on trigger or a value belonging to a set) I can fairly easily concevie a projector (which would be a class transforming a vector in a vector, but not with a a matrix, but with computed rules ). @Mark Jansen +1 are you telepath ? Yes a key collision operator would be nice : given for instance an apache log, I will have segments of path, and I may want keys to be the accumulated graph of a user on a website. so my collision rule might be : (key being the referer value the page visited afterwards) dict( a = b, a = c ) + dict( b = e ) = dict( a = dict( b = e ), a = c) I thought of it, but I really loved the conservation rule. And I feared people would think of it as too complicated. Keep It Simple I learnt :) @all Wrapping everything to logicial sense. I was thinking of supersets of object (thus out of the stdlib) that would have different algebrae and could be used as casts on object to redifine + - * / cos & | ^ and for different objects would behave consistently ex : vector( dict ) vector( list ) vector( string ) would make dict & list & string behave like vectors thus mainly supporting elementwise operations sets( dict ) , sets( string ) ... would make dict string be sets of elements ... (with the original dict addition design of GvR et al) Each superset would have a unit test for the operation verifying that behaviour is consistent. (associativity, distributivity, ...) what about this solution ? -- Friendly jul [View Less]

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Public feedback tools (Was: working on a PEP for the __preview__ package)
by anatoly techtonik Jan. 4, 2012

Jan. 4, 2012

On Wed, Jan 4, 2012 at 4:34 AM, Nick Coghlan <ncoghlan(a)gmail.com> wrote: > On Wed, Jan 4, 2012 at 1:47 AM, anatoly techtonik <techtonik(a)gmail.com> > wrote: > > Before attempting any library refactoring or addition, I would first > think > > about placing a feedback mechanism in place to collect public response > about > > satisfaction with current stdlib contents, and collecting proposals about > > parts that should be included into stdlib (… [View More]

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