Re: Minimal binary diff & version control in Python?

[Kevin Ar18] > Has anyone ever tried to implement some form of version control in Python (if > so, where)? Yes. Here's the code I use to read and write my old version control files (originally created with TLIB): http://code.activestate.com/recipes/576729/ Raymond -- http://mail.python.org

Geohashing

import hashlib def geohash(latitude, longitude, datedow): '''Compute geohash() in http://xkcd.com/426/ >>> geohash(37.421542, -122.085589, b'2005-05-26-10458.68') 37.857713 -122.544543 ''' h = hashlib.md5(datedow).hexdigest() p, q = [('%f' % float.fromhex('0.' + x)) for x

Re: sorting items in a table problematic because of scientific notation

[John Machin] > > 'NEAR_DIST'], [('N', 9, 0), ('N', 9, 0), ('F', 19, 11)], [53, 55, ' > > The data type code for the offending column is "F" which is not in the > bog-standard dBase III set of C, N, D, and L. The code that you have used > merely > returns unchanged the character string that finds

Re: Get item from set

[bearophileh...@lycos.com] > But some other times you may accept to change the class and the set/ > dict, making it tell apart the keys only when they are different > object: > > class Some(object): >     def __init__(self, y): >         self._y = y >     def __eq__(self, other): >         return s

Re: Generating all combinations

> What, no partitions? > > http://en.wikipedia.org/wiki/Partition_of_a_set Seems like you could roll your own (using combinations as a starting point): def pairwise(iterable): a, b = tee(iterable) next(b, None) return izip(a, b) def partition(s): n = len(s) for i in range(n):

Re: Generating all combinations

> > What, no partitions? > > >http://en.wikipedia.org/wiki/Partition_of_a_set Simpler version: def partition(s): n = len(s) parts = range(1, n) for i in range(n): for div in combinations(parts, i): print map(s.__getslice__, chain([0], div), chain(div, [n])) >>> pa

Re: Generating all combinations

> Nice one! It only does partitions of a sequence. I haven't yet looked at a way to do partitions of a set. Any ideas? > Raymond, as perhaps *the* principle contributor to itertools, do you feel > that the combinatorics-related tools should be in their own module? Or is > that dividing the mod

Re: named tuple mutability

> Should tuples be named? Yes. -- http://mail.python.org/mailman/listinfo/python-list

Re: What's a call-tip to do?

On May 14, 8:24 am, Tal Einat <[EMAIL PROTECTED]> wrote: > I just ran into this. In IDLE (Python 2.5), the call-tip for > itertools.count is: > "x.__init__(...) initializes x; see x.__class__.__doc__ for signature" My IDLE (1.2.2 running on Python 2.5.2) has the correct call-tip. I don't know why

Re: Classmethods are evil

On May 16, 9:01 pm, Ivan Illarionov <[EMAIL PROTECTED]> wrote: > After re-reading "Python is not Java" I finally came to conclusion that > classmethods in Python are a very Bad Thing. Sounds like a serious case of mis-learning. Class methods are the preferred way to implement alternate constructo

Re: Optimization: Picking random keys from a dictionary and mutating values

On May 28, 4:41 pm, blaine <[EMAIL PROTECTED]> wrote: > 1.  Whats a good way to get the keys? I'm using a loop with > random.choice() at the moment. Why not keep a separate list of keys and use random.sample()? Raymond -- http://mail.python.org/mailman/listinfo/python-list

Re: How to add function return value

On May 30, 6:21 pm, HYRY <[EMAIL PROTECTED]> wrote: > Can I write a decorator that it can automately do this conversion > > def func1() >     a = 1 > > ---> > > def func1(): >     a = 1 >     return locals() Not sure why you would want to do this, but there are several ways. 1. Make bytecode hack

Re: Nasty gotcha/bug in heapq.nlargest/nsmallest

On May 15, 12:06 am, Peter Otten <[EMAIL PROTECTED]> wrote: > According > to my ad hoc test you need <, <=, and == for nlargest()/nsmallest() to > work: In Py2.6 and after, you only need < and ==. I replaced the LE tests with LT to match list.sort() and bisect.bisect(). The == arises because nla

Re: Merging ordered lists

On May 31, 10:00 pm, etal <[EMAIL PROTECTED]> wrote: > Here's an algorithm question: How should I efficiently merge a > collection of mostly similar lists, with different lengths and > arbitrary contents, while eliminating duplicates and preserving order > as much as possible? I would do it two s

Re: Merging ordered lists

> Thanks for the tip; itertools never ceases to amaze. One issue: > groupby doesn't seem to remove all duplicates, just consecutive ones > (for lists of strings and integers, at least): > > >>> [k for k, g in itertools.groupby(list("asdfdfffdf"))] > > ['a', 's', 'd', 'f', 'd', 'f', 'd', 'f'] That'

Re: defaultdict.fromkeys returns a surprising defaultdict

On Jun 3, 1:11 pm, Matthew Wilson <[EMAIL PROTECTED]> wrote: > I used defaultdict.fromkeys to make a new defaultdict instance, but I > was surprised by behavior: > >     >>> b = defaultdict.fromkeys(['x', 'y'], list) > >     >>> b >     defaultdict(None, {'y': , 'x': }) > >     >>> b['x'] >     >

Re: defaultdict.fromkeys returns a surprising defaultdict

On Jun 3, 1:11 pm, Matthew Wilson <[EMAIL PROTECTED]> wrote: > I used defaultdict.fromkeys to make a new defaultdict instance, but I > was surprised by behavior: >     >>> b = defaultdict.fromkeys(['x', 'y'], list) >     >>> b >     defaultdict(None, {'y': , 'x': }) One other thought: Even after

Re: marshal.dumps quadratic growth and marshal.dump not allowing file-like objects

On Jun 15, 1:04 am, [EMAIL PROTECTED] wrote: > However it seems that marshal.dumps() for large objects has a > quadratic performance issue which I'm assuming is that it grows its > memory buffer in constant increments. Looking at the source in http://svn.python.org/projects/python/trunk/Python/ma

Re: marshal.dumps quadratic growth and marshal.dump not allowing file-like objects

On Jun 15, 8:08 am, [EMAIL PROTECTED] wrote: > Indeed. I (the OP) am using a production release which has the 1k > linear growth. > I am seeing the problems with ~5MB and ~10MB sizes. > Apparently this will be improved greatly in Python 2.6, at least up to > the 32MB limit. I've just fixed this fo

Re: 'string'.strip(chars)-like function that removes from the middle?

On Jun 16, 10:09 am, Peter Otten <[EMAIL PROTECTED]> wrote: > Ethan Furman wrote: > > The strip() method of strings works from both ends towards the middle. > > Is there a simple, built-in way to remove several characters from a > > string no matter their location? (besides .replace() ;) > >>> iden

Re: sorted or .sort() ?

On Jun 16, 5:11 am, Peter Bengtsson <[EMAIL PROTECTED]> wrote: > My poor understanding is that the difference between `sorted(somelist, > key=lambda x:...)` and `somelist.sort(lambda x,y...)` is that one > returns a new list and the other sorts in-place. > > Does that mean that .sort() is more effi

Re: string.Template.delimiter cannot be overriden?

On Jun 16, 9:53 pm, kretik <[EMAIL PROTECTED]> wrote: > I've been trying to coax this class to use something other than the > default '$' but it seems setting it to something else has no discernible > effect. Is it necessary to inherit from the class to do this? Yes, subclassing is the intended wa

Re: Hamming Distance

On Jun 19, 4:27 pm, godavemon <[EMAIL PROTECTED]> wrote: > I need to calculate the Hamming Distance of two integers.  The hamming > distance is the number of bits in two integers that don't match.  I > thought there'd be a function in math or scipy but i haven't been able > to find one.  This is my

Re: Hamming Distance

Non-recursive, 8-bit block table lookup version: def ham(a, b, ht=[hamdist(a,0) for a in range(256)]): x = a ^ b dist = 0 while x: dist += ht[x & 255] x >>= 8 return dist Raymond -- http://mail.python.org/mailman/listinfo/python-list

Re: An idiom for code generation with exec

On Jun 20, 5:03 am, eliben <[EMAIL PROTECTED]> wrote: > I've rewritten it using a dynamically generated procedure > for each field, that does hard coded access to its data. For example: > > def get_counter(packet): >   data = packet[2:6] >   data.reverse() >   return data > > This gave me a huge sp

Re: string.Template.delimiter cannot be overriden?

[kretik] >> I've been trying to coax this class to use something other than the > >> default '$' but it seems setting it to something else has no discernible > >> effect. Is it necessary to inherit from the class to do this? [raymond] > > Yes, subclassing is the intended way to produce variants of

Re: Nested generator caveat

On Jul 3, 9:20 pm, "Dieter Maurer" <[EMAIL PROTECTED]> wrote: > The apparent reason is that the free variables in > nested generator definitions are not bound (to a value) at invocation > time but only at access time. That's what it is supposed to do. Welcome to a dynamic language. Raymond --

Re: Perfect hashing for Py

On Jul 11, 3:01 pm, [EMAIL PROTECTED] wrote: > I have found this perfect hash (minimal too) > implementation:http://burtleburtle.net/bob/hash/perfect.html > > I have already translated part of it to D, and it seems to work well > enough. As discussed in the PyConDue, I think this may be used in >

Re: Perfect hashing for Py

On Jul 12, 10:13 am, Raymond Hettinger <[EMAIL PROTECTED]> wrote: > On Jul 11, 3:01 pm, [EMAIL PROTECTED] wrote: > > > I have found this perfect hash (minimal too) > > implementation:http://burtleburtle.net/bob/hash/perfect.html > > > I have already translated

Re: new itertools functions in Python 2.6

On Jul 14, 1:26 pm, Mensanator <[EMAIL PROTECTED]> wrote: > ##  Combinations with replacement > ##  - > ##  aaa aab aac aad aae abb abc abd abe acc acd ace > ##  add ade aee bbb bbc bbd bbe bcc bcd bce bdd bde > ##  bee ccc ccd cce cdd cde cee ddd dde dee eee > ## > ##  

Re: __del__ methods

On Jul 18, 11:31 am, Jason Baker <[EMAIL PROTECTED]> wrote: > I have a class that I need to do some finalization on when it dies.  I > know I can use the __del__ method, but I seem to recall that it > impedes garbage collection.  Is this the case? FWIW, I know a good number of top notch Python pro

Re: atan2 weirdness

On Jul 19, 9:12 pm, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > hi > > atan2 is supposed to return the angle to x-axis when given y and x, I > suppose if I take [x,y] to one full circle, I should get 0-360 degree > back but no, I get 3 full revolutions! > maybe my understanding is wrong. >

Re: Question

On Jul 19, 2:27 am, [EMAIL PROTECTED] wrote: > Why is Perl so much better than python? Because dollar signs are a superior form of punctuation. Raymond -- http://mail.python.org/mailman/listinfo/python-list

Re: persistent deque (continued)

On Jul 21, 12:08 pm, castironpi <[EMAIL PROTECTED]> wrote: > Some time ago, I was asking about the feasibility of a persistent > deque, a double-ended queue. > > It runs into the typical space allocation problems.   Try starting with a dict-based implementation of a double-ended queue ( http://asp

Re: convert list of lists to list

On Jul 22, 8:25 am, Fredrik Lundh <[EMAIL PROTECTED]> wrote: > if there's only one level of recursion, and the lists aren't too long, > you can simply do: > >      sum(list_of_lists, []) > > (this has quadratic performance, so don't use it for large structures) For linear performance, you can use

Re: seemingly simple list indexing problem

[Ervan Ensis] > I have a list like [108, 58, 68].  I want to return > the sorted indices of these items in the same order > as the original list.  So I should return [2, 0, 1] One solution is to think of the list indexes being sorted according the their corresponding values in the input array: >

Re: Optimizing size of very large dictionaries

> > Are there any techniques I can use to strip a dictionary data > > structure down to the smallest memory overhead possible? Sure. You can build your own version of a dict using UserDict.DictMixin. The underlying structure can be as space efficient as you want. FWIW, dictionaries automaticall

Re: random numbers according to user defined distribution ??

On Aug 6, 3:02 pm, Alex <[EMAIL PROTECTED]> wrote: > I wonder if it is possible in python to produce random numbers > according to a user defined distribution? > Unfortunately the random module does not contain the distribution I > need :-( Sure there's a way but it won't be very efficient. Start

Re: reading dictionary's (key,value) from file

On Apr 7, 9:38 am, [EMAIL PROTECTED] wrote: > Folks, > Is it possible to read hash values from txt file. > I have script which sets options. Hash table has key set to option, > and values are option values. > > Way we have it, we set options in a different file (*.txt), and we > read from that file

Re: list.sort(): heaviest item?

On Apr 8, 8:15 am, "Steven Clark" <[EMAIL PROTECTED]> wrote: > If I have a list of items of mixed type, can I put something into it > such that after a list.sort(), is guaranteed to be at the end of the > list? Since the other guys gave you the real answer, how about this: sentinel = object() myl

Re: Little novice program written in Python

> What I would like is to receive some criticism to my code to make it more > Python'esque and, possibly, use the resources of the computer in a more > efficient way (the algorithm implemented below is the Sieve of Eratosthenes): It looks like straight-forward code and is fine as it stands. If you

Re: Feature suggestion: sum() ought to use a compensated summation algorithm

On May 3, 9:50 am, Szabolcs Horvát <[EMAIL PROTECTED]> wrote: > I did the following calculation:  Generated a list of a million random > numbers between 0 and 1, constructed a new list by subtracting the mean > value from each number, and then calculated the mean again. > > The result should be 0,

Re: Feature suggestion: sum() ought to use a compensated summation algorithm

> > > However I find the seccond argument hack ugly. Does the sum way have any > > > performance advantages over the reduce way? > > > Yes, sum() is faster: ... > Not really; you measure the import and the attribute access time in > the second case. sum() is 2x faster for adding numbers only: Try

Re: Overwriting property-> can't set attribute

On Aug 22, 5:38 am, Gregor Horvath <[EMAIL PROTECTED]> wrote: > why is this code failing? > > class B(object): >      pass > > B.testattr = property(lambda s:"hallo") > b = B() > b.testattr = "test" First, property() only works when attached to classes, not instances. So the assignment should be:

Re: property() usage - is this as good as it gets?

of property() that allows you to re-use the same getter/setter code for multiple attributes: http://code.activestate.com/recipes/205126/ Raymond Hettinger -- http://mail.python.org/mailman/listinfo/python-list

Re: What is class method?

On Aug 24, 5:32 am, Hussein B <[EMAIL PROTECTED]> wrote: > Hi, > I'm familiar with static method concept, but what is the class method? > how it does differ from static method? when to use it? I use them when I need alternative constructors for a class. class Angle(object): def __init__(self,

Re: use of Queue

On Aug 27, 4:55 pm, Paul Rubin wrote: > [EMAIL PROTECTED] writes: > > Or make the consumers daemon threads so that when the producers are finished > > an all non-daemon threads exit, the consumers do as well. > > How are the consumers supposed to know when the producers a

Re: Which is faster?

On Aug 29, 9:26 pm, cnb <[EMAIL PROTECTED]> wrote: > def av_grade(self): >      return sum(review.grade for review in self.reviews) / \ >               len(self.reviews) Minor point. Consider making the divisor: float(len(self.reviews)). It would be a bummer to throw-off the average because of f

Re: dict.update

On Sep 2, 8:04 am, Mike P <[EMAIL PROTECTED]> wrote: > Hi All, > > I have two dictionaries e.g > dict1 = {123:3,234:5,456:3} > dict2 = {123:4,157:2,234:5,456:3,567:2} > > I want to merge these two dictionaries together so i have a resultant > dictionary of: > > dict3 = {123:[4,3],157:[2,0],234:[5,5

Re: Profiling, sum-comprehension vs reduce

On Sep 13, 9:27 pm, Hrvoje Niksic <[EMAIL PROTECTED]> wrote: > Note that, despite appearances, it's not as built-in as one might > wish.  sum(seq) is still completely generic and works on all > number-like objects (in fact on all objects that define an __add__ > operation except strings, which are

Re: time series calculation in list comprehension?

[Peter Otten] > from __future__ import division > > from itertools import islice, tee, izip . . . > def moving_average2(items, n): > first_items, last_items = tee(items) > accu = sum(islice(last_items, n-1)) > for first, last in izip(first_items, last_items): > accu += last >

Re: "RuntimeError: dictionary changed size during iteration" ; Good atomic copy operations?

[robert] > In very rare cases a program crashes (hard to reproduce) : > > * several threads work on an object tree with dict's etc. in it. Items > are added, deleted, iteration over .keys() ... ). The threads are "good" > in such terms, that this core data structure is changed only by atomic > oper

Re: Q's: pythonD and range(1,12)

John Savage wrote: > Could > someone please explain the rationale behind python designers' thinking > in deciding the function "range(1,12)" should return the sequence 1 to > 11 rather than the more intuitively-useful 1 to 12?? There are several ways to do this, closed intervals, half-open interva

Re: Global Threading Lock 2 - Re: "RuntimeError: dictionary changed size during iteration"..

[robert] > That queue/passing-through-only-an-extra-global-var communication is > acceptable for thin thread interaction. > ( hope this extra global var is thread-safe in future Python's :-) ) > > But "real" thread-programming should also be possible in Python - and it > is with the usual disciplin

Re: "RuntimeError: dictionary changed size during iteration" ; Good atomic copy operations?

[robert] > In very rare cases a program crashes (hard to reproduce) : > > * several threads work on an object tree with dict's etc. in it. Items > are added, deleted, iteration over .keys() ... ). The threads are "good" > in such terms, that this core data structure is changed only by atomic > oper

Re: Memory visualization

[bearophile] > During the execution of a Icon script there are ways to visualize the > memory: > http://www.cs.arizona.edu/icon/progvis/memmon/memmon.htm . . . > I'd like to know if for Python there is a similar program to > dynamically see the memory in a similar way. > If such tool doesn't exist

Re: trying to find repeated substrings with regular expression

[Robert Dodier] > I'm trying to find substrings that look like 'FOO blah blah blah' > in a string. For example give 'blah FOO blah1a blah1b FOO blah2 > FOO blah3a blah3b blah3b' I want to get three substrings, > 'FOO blah1a blah1b', 'FOO blah2', and 'FOO blah3a blah3b blah3b'. No need for regular

TaskQueue

I would like to get feedback on an idea I had for simplifying the use of queues with daemon consumer threads Sometimes, I launch one or more consumer threads that wait for a task to enter a queue and then work on the task. A recurring problem is that I sometimes need to know if all of the tasks ha

Re: Good thread pool module

David Hirschfield wrote: > There isn't a thread pool module in the standard library, but I'm sure > many have been written by people in the python community. > Anyone have a favorite? Is there one particular implementation that's > recommended? Because of the GIL, thread pools are not as useful in

Re: Sorting a list of objects by multiple attributes

[George Young] >> For multiple keys the form is quite analogous: >> >> L.sort(key=lambda i: (i.whatever, i.someother, i.anotherkey)) [Noah] > If you are lambda-phobic (as I am) this should also work for an > arbitrary set of attributes: > > attrs = 'attr1 attr2 attr3'.split() > sortlist = [[getat

Re: Manipulating sets from the 2.4 C API?

Dave Opstad wrote: > I just looked through the Python/C API reference for 2.4.3 and didn't > see anything about using sets. I'd been expecting things like PySet_New, > PySet_Check etc. In Py2.4, there was not a custom set C API because the module was still ungoing significant development. For 2.4

Re: Sorting a list of objects by multiple attributes

Azolex: > Let's push the diagnosis a bit further : the aversion to the keyword > "lambda" has to do with the fact that it ignores the english word used > by all non-geeks to convey the meaning, eg "given" Right. However, Guido has said that lambda is here to stay, so it's time to get over it. R

Re: Sorting a list of objects by multiple attributes

[Noah] > I suggested the above because it wasn't obvious to me how one would > pass the arbitrary set of attributes to the lambda expression (and I > envisioned them being specified as strings in this case, since the set > of attributes will be coming from a web form). > > So what about the followi

Re: list.clear() missing?!?

[Steven Bethard] > I think these are all good reasons for adding a clear method, but being > that it has been so hotly contended in the past, I don't think it will > get added without a PEP. Anyone out there willing to take out the best > examples from this thread and turn it into a PEP? Somethin

Re: list.clear() missing?!?

[Felipe Almeida Lessa] > > I love benchmarks, so as I was testing the options, I saw something very > > strange: > > > > $ python2.4 -mtimeit 'x = range(10); ' > > 100 loops, best of 3: 6.7 msec per loop > > $ python2.4 -mtimeit 'x = range(10); del x[:]' > > 100 loops, best of 3: 6.35 msec

Re: list.clear() missing?!?

> > * the request is inane, the underlying problem is trivial, and the > > relevant idiom is fundamental (api expansions should be saved for rich > > new functionality and not become cluttered with infrequently used > > redundant entries) > > Is this sort of editorialising fair, or just a way of no

Re: list.clear() missing?!?

[Dan Christensen] > It's true that this runs at the same speed as the del variants on my > machine. That's not too surprising to me, but I still don't > understand why the del variants are more than 5% faster than the first > version. Understanding it involves looking at implementation specific d

Re: Feature request: String-inferred names

[Gregory Ewing] > >>I just posted to my blog about a feature that I'd like to see added to > >>Python. > > >>http://alphaios.blogspot.com/2009/11/python-string-inferred-names-wor... > > I don't think getattr and setattr are used anywhere near > frequently enough to justify special syntax. Perhaps

Re: python bijection

[Joshua Bronson] > Raymond, do you think there might be any future in including a built- > in bidict data structure in Python? I don't think so. There are several forces working against it: * the recipe is new, so it hasn't had a chance to mature or to gain a fan club. * there are many approa

Re: python bijection

[Me] > > * we've already got one (actually two). > >   The two dictionary approach... [Francis Carr] > Solutions such as bidict just automate the two-dict approach. They do so at the expense of implementing a new API to support it and at the expense with having non-obvious behaviors (i.e. how it

Re: python bijection

> >   ...sqlite3 provides another way... > > In many many cases, using a dB (even a lightweight such as sqlite3) is > swatting the fly with a sledgehammer :-) I'm sure it seems that way, but look at the generic description of the problem: "I have a list of n-ary tuples with named fields and would

Re: Are routine objects guaranteed mutable & with dictionary?

On Dec 4, 2:03 am, "Alf P. Steinbach" wrote: > Is this guaranteed to work in Python 3.x? > >  >>> def foo(): pass > ... >  >>> foo.blah = 222 >  >>> foo.blah > 222 Yes, function attributes are guaranteed to be writable: http://www.python.org/dev/peps/pep-0232/ Raymond -- http://mail.python.o

Re: Float precision and float equality

On Dec 5, 7:37 am, Anton81 wrote: > I'd like to do calculations with floats and at some point equality of > two number will be checked. > What is the best way to make sure that equality of floats will be > detected, where I assume that mismatches beyond a certain point are > due to truncation erro

Re: Float precision and float equality

On Dec 5, 12:56 pm, Mark Dickinson wrote: > On Dec 5, 8:25 pm, Raymond Hettinger wrote: > > > On Dec 5, 7:37 am, Anton81 wrote: > > > > I'd like to do calculations with floats and at some point equality of > > > two number will be checked. > > >

Re: python bijection

[geremy condra] > I actually considered using dependencies as an example on the > "graphine for pythonistas"[1] article, but decided to do the maze > run instead. In any event, the uses of graphs in general computing > are well enough established that I don't really think that's where > the majorit

Re: python bijection

On Dec 5, 3:22 pm, geremy condra wrote: > On Sat, Dec 5, 2009 at 4:39 PM, Raymond Hettinger wrote: > > [geremy condra] > >> I actually considered using dependencies as an example on the > >> "graphine for pythonistas"[1] article, but decided to do the maz

Re: Float precision and float equality

On Dec 5, 11:42 pm, Tim Roberts wrote: > Raymond Hettinger wrote: > > >   if not round(x - y, 6): ... > > That's a dangerous suggestion.  It only works if x and y happen to be > roughly in the range of integers. Right. Using abs(x-y) < eps is the way to go. Raymo

Re: Float precision and float equality

[Carl Banks] > > You're talking about machine epsilon?  I think everyone else here is > > talking about a number that is small relative to the expected smallest > > scale of the calculation. That was also my reading of the OP's question. The suggestion to use round() was along the lines of perfor

Efficient Running Median

I've updated the running median recipe to use a new algorithm with O (log n) updates for a large sliding window traversing a data stream. See http://code.activestate.com/recipes/576930/ The engine is a new collection class called IndexableSkiplist. It is like a regular skiplist as detailed at htt

Re: Performance of lists vs. list comprehensions

[Wolfram Hinderer] > Yes, list building from a generator expression *is* expensive. And > join has to do it, because it has to iterate twice over the iterable > passed in: once for calculating the memory needed for the joined > string, and once more to actually do the join (this is implementation >

Re: Sorted dictionary

On Jan 20, 5:02 pm, "Jan Kaliszewski" wrote: > Hello, > > Inspired by some my needs as well as some discussions in the net, I've   > implemented a sorted dictionary (i.e. a dict that returns keys, values and   > items always sorted by keys): > > http://code.activestate.com/recipes/576998/ > > Mayb

Re: Consume an iterable

On Jan 22, 6:13 am, Muhammad Alkarouri wrote: > In the python help for itertools, the following function is provided: > > def consume(iterator, n): >     "Advance the iterator n-steps ahead. If n is none, consume > entirely." >     collections.deque(islice(iterator, n), maxlen=0) > > What is the a

Re: list.pop(0) vs. collections.dequeue

[Steve Howell] > Why wouldn't you get a competent C programmer simply make > list_ass_slice smart enough to make list.pop(0) O(1)? When this suggestion was discussed on python-dev years ago, it was rejected. One reason is that it was somewhat common for C code to access the list data structure di

Re: Consume an iterable

>      def consume2(iterator, n):  # the approved proposal (see #7764) >          if n is None: >              collections.deque(iterator, maxlen=0) >          else: >              next(islice(iterator, n, n), None) FWIW, the deque() approach becomes even faster in Py2.7 and Py3.1 which has a high

Re: Is defaultdict thread safe?

On Jan 25, 12:59 am, "Frank Millman" wrote: > Hi all > > Is defaultdict thread safe? Sometimes. It depends on whether an operation has callbacks to pure Python. > Assume I have - > >     from collections import defaultdict >     my_dict = defaultdict(list) > > If two threads call "my_dict['abc

Re: flow control and nested loops

On Sep 25, 12:01 pm, kj wrote: > In Perl, one can label loops for finer flow control.  For example: > > X: for my $x (@X) { >   Y: for my $y (@Y) { >     for my $z (@Z) { >       next X if test1($x, $y, $z); >       next Y if test2($x, $y, $z); >       frobnicate($x, $y, $z); >     } >     glortz(

Re: Business issues regarding adapting Python

On Sep 27, 12:13 am, Nash wrote: > Hello everyone, > > I'm a big time python fan and it has helped me write code fast and > push it out quickly. We have a medium sized telecom product written > 90% in Python and 10% in Java. The problem is, in the place where we > work (Pakistan), we can't find Py

Re: Q: sort's key and cmp parameters

On Oct 1, 10:08 am, kj wrote: > Challenge: to come up with a sorting task that cannot be achieved > by passing to the sort method (or sorted function) suitable values > for its key and reverse parameters, but instead *require* giving > a value to its cmp parameter. If you're assuming a consistent

Re: Fast decimal arithmetic module released

[Stefan Krah] > today I have released the following packages for fast arbitrary precision > decimal arithmetic: Nice. Raymond -- http://mail.python.org/mailman/listinfo/python-list

Re: Q: sort's key and cmp parameters

[Paul Rubin] > Yes, think of sorting tree structures where you have to recursively > compare them til you find an unequal pair of nodes.   I'm not sure what you mean by this. What are the semantics of sorting a tree? Can you outline an example of tree that could be sorted easily with a cmp funct

Re: Q: sort's key and cmp parameters

[Paul Rubin] > The idea was that you have a list of trees that you want to sort, and > an ordering relation between trees: > >    def gt(tree1, tree2): ... > > where you recursively descend both trees until you find an unequal > pair of nodes.  You're not trying to sort the nodes within a single >

Re: Q: sort's key and cmp parameters

[Paul Rubin] > The idea was that you have a list of trees that you want to sort, and > an ordering relation between trees: > >    def gt(tree1, tree2): ... Are the trees user defined classes? Can the gt() function be added incorporated as __lt__ method so that you can just run a plain sort:

Re: Q: sort's key and cmp parameters

[Paul Rubin] > Example of list of trees (nested dicts). In practice you could get > such a list from the simplejson module: > > list_of_trees = [{'value':1, 'left':{'value':3,'left':None,'right':None}, >'right':{'value':7,'left':{'value':5, ...}}}, >

Re: Q: sort's key and cmp parameters

> > So, it looks like the relevant comparison values can be stored in > > nested lists: > > >list_of_lists = \ > > [[1, [3, [], []], > > [7, [5, [], []], []]], > > [19, [23, [], []], > > []], > > ] > > Now you've copied all the data out of the original tree,

Re: Q: sort's key and cmp parameters

> > >  Say you want to change the numeric comparisons so that > > > even numbers always sort before odd numbers, ie. > > >     -4 < -2 < 0 < 2 < 4 < ... < -999 < ... -1 < 1 < 3 ... > > > This is too easy: > > >     >>> s = [-2, 4, 2, -1, -3, 1, -4, 0, 3] > >     >>> s.sort() > >     >>> s.sort(key=

Re: Q: sort's key and cmp parameters

[bearophile] > I love the 'key', it makes my code simpler and it's simpler to > understand. I am not opposed to the idea of keeping cmp, that in some > rare cases may be useful or more natural. > > The problem is that if you allow to use the cmp, lot of programmers > will use it straight away, not

Re: bug with itertools.groupby?

On Oct 6, 4:06 pm, Kitlbast wrote: > Hi there, > > the code below on Python 2.5.2: > > from itertools import groupby > > info_list = [ >     {'profile': 'http://somesite.com/profile1', 'account': 61L}, >     {'profile': 'http://somesite.com/profile2', 'account': 64L}, >     {'profile': 'http://som

Re: Q: sort's key and cmp parameters

[Hrvoje Niksic] > Note that stable sort has additional memory requirements.  In situations > where you don't need stability, but do need memory-efficient in-place > sorting, an unstable sort might well be preferred.  This is why > libraries such as C++'s STL offer both. FWIW, the "additional memor

Re: Neural networks in python

On Oct 7, 10:53 pm, ruchir wrote: > I want to design and train a neural network in python. Can anyone > guide me, from where can I get some useful material/eBook/libraries > etc. for the same. I have no prior experience in neural netwoks and > want to implement it urgently. > Thanks in advance :)

Re: The rap against "while True:" loops

[kj] > I use "while True"-loops often, and intend to continue doing this > "while True", but I'm curious to know: how widespread is the > injunction against such loops?  Has it reached the status of "best > practice"? This is the first I've ever heard of such an quasi-injunction. Like you, I use "

<    1   2   3   4   5   6   7   8   >