Re: [Tutor] Help Optimise Code
On a small side note, the docs say array.array is supposed to be
efficient. Testing has shown in this function, a list is faster (at
least for x<10). A set is faster still - at least over the same
range on my computer,, but you can't guarantee ordering, which makes
it inconsistent - and potentially broken.
The version I've got in my original post (using a single variable and
short-circuiting logic) is almost twice as fast as the version using
two separate tests. I don't know why, so suggestions would be
appreciated.
I'll add in a version of the count6 function. I must have forgotten
that maths lesson.
I've just thought of something that might be faster than using mod,
but I'll have to wait until I get home to test it.
(using a list of itertools.cycle's to produce a true/false from a
tuple with prime length, yielding a number iff not any(l[:sqrtX]). No
division involved...) If that make no sense to anyone, it makes less
sense to me, sounds ok, though...
---
Richard "Roadie Rich" Lovely
Part of the JNP|UK Famille
www.theJNP.com
(Sent from my iPod - please allow me a few typos: it's a very small
keyboard)
On 19 Nov 2008, at 09:26 PM, Lie Ryan <[EMAIL PROTECTED]> wrote:
On Wed, 19 Nov 2008 13:13:18 +, Richard Lovely wrote:
I'm pretty new to code optimisation, so I thought I'd ask you all for
advice.
I'm making an iterative prime number generator. This is what I've
got so
far:
Code: Select all
import math, array
def count2(start_at=0):
'Yield every third integer, beginning with start_at'
# this has been
tested as faster than using itertools.count
while True:
yield start_at
start_at += 2
def iprimes():
'generate an endless sequence of prime numbers'
yield 2
yield 3
yield 5
sqrt = math.sqrt
# 'L' for unsigned long - not tested if
# using a smaller type is faster
knownPrimes = array.array("L",(3,5))
for x in count2(7):
# take extra function calls out of the inner loop
sqrtX = sqrt(x)
for p in knownPrimes:
test = (not x % p) and -1 or p > sqrtX
if test == -1: # (not > x % p) == true
break
elif test: # (p > sqrtX) == true
yield x
knownPrimes.append(x)
break
Do you know that every prime number is in the form 6*x+1 or 6*x-1,
except
2 and 3. This means that instead of checking all odd numbers, you
could
loop over 6 numbers then yield n - 1 and n + 1.
def count6(start):
while True:
start += 6
yield start - 1
yield start + 1
And I've seen that you generated prime by dividing things up (actually
modulus). Division and modulus is the slowest arithmetic operator,
avoid
it if you can. If you knows the upper bound beforehand, it is faster
to
use multiplication and an array of fixed size, i.e. "Sieve of
Erasthotenes". If you intend to generate primes without known upper
bound
though, using sieve complexify things up.
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Re: [Tutor] Decimal fixed point representation
Hi Alan That's right, it is the Decimal module I'm trying to understand. And, it is how to represent a decimal floating point number as a common/vulgar fraction eg 1.234 = 1234/1000. How do you do this using the Decimal module? The motivation is to avoid floating point calculations and use integers only (don't ask why!). Cheers! Dinesh Date: Fri, 21 Nov 2008 01:03:05 - From: "Alan Gauld" <[EMAIL PROTECTED]> Subject: Re: [Tutor] Decimal fixed point representation To: tutor@python.org Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original "Dinesh B Vadhia" <[EMAIL PROTECTED]> wrote > I'm trying to get my head around the Decimal module to > understand how to represent a decimal floating point > number as an integer (or integers). I'm not sure what you mean by that. Is it the use of the Decimal module you are querying? Is it how to represent a ecimal fraction as an integer - ie how to lose the numbers after the point? Is it how to represent it as a common/vulgar fraction eg 1.234 = 1234/1000 Or something else? > Am I barking mad or is this possible? It is possible that you are barking mad I suppose. As to whether what you are asking about decimals is possible, that depends on what you are actually asking :-) Alan G ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Decimal fixed point representation
On Fri, Nov 21, 2008 at 8:22 AM, Dinesh B Vadhia <[EMAIL PROTECTED]> wrote: > Hi Alan > > That's right, it is the Decimal module I'm trying to understand. And, it is > how to represent a decimal floating point number as a common/vulgar fraction > eg 1.234 = 1234/1000. How do you do this using the Decimal module? The > motivation is to avoid floating point calculations and use integers only > (don't ask why!). Cheers! The Decimal type does not represents numbers as fractions, it represents them as decimal floating point, i.e. a floating point representation using base 10 instead of base 2. A fractions module was introduced in Python 2.6 that does represent numbers as a numerator and denominator: http://docs.python.org/library/fractions.html Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] python reverse engineering tools
Can somebody tell me about any python to UML reverse engineering tools . I was trying pynsource but it uses the old opengl namespace (this is what i assume the problem is from what i read from the openGL documentation) and thus it gives an import error from wxPython.ogl import * ImportError: No module named ogl now i tried changing it to (again from documentation) import wx.lib.ogl as ogl but it still does not work. Can somebody tell me what the problem might be . -- A-M-I-T S|S ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] import data (txt/csv) into list/array and manipulation
Cool, Does anyone else have any other thoughts on this problem? -- View this message in context: http://www.nabble.com/import-data-%28txt-csv%29-into-list-array-and-manipulation-tp20424075p20623480.html Sent from the Python - tutor mailing list archive at Nabble.com. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Decimal fixed point representation
On Fri, Nov 21, 2008, Dinesh B Vadhia wrote: > > That's right, it is the Decimal module I'm trying to understand. And, > it is how to represent a decimal floating point number as a > common/vulgar fraction eg 1.234 = 1234/1000. How do you do this using > the Decimal module? The motivation is to avoid floating point > calculations and use integers only (don't ask why!). Cheers! I can understand why if one is writing accounting applications that have to be accurate to the penny (or whatever in the local currency). Accountants and auditors don't like rounding errors. The accounting system I wrote in the mid-80s, and still use today, is written mostly in C, and handles all monitary calculations in cents in long integers with appropriate input and output routines to make them look to the world as it would expect. There was (is?) a FixedPoint package in python that I use for handling dollar amounts. It came out before the Decimal type, and I am not fixing something that works. The only machines I worked on extensively that handled decimal arithmatic very well were the Burroughs Medium Systems B-2500 through B-4800 which did everything in decimal which made a lot of sense since they were designed primarily to run COBOL accounting applications. Bill -- INTERNET: [EMAIL PROTECTED] Bill Campbell; Celestial Software LLC URL: http://www.celestial.com/ PO Box 820; 6641 E. Mercer Way Voice: (206) 236-1676 Mercer Island, WA 98040-0820 Fax:(206) 232-9186 Scientists are explorers. Philosophers are tourists. -- Richard Feynman ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] python question
Hi I have just joined this list. I need some help working on a Python application I am working on. I am working on a quiz game where the users gain points when the answer questions correctly. I have written the skeleton of the quiz with If, Elif and Else statements. it runs perfectly. I am very unclear on how to score points at the end of each round and how to import images. Can anyone help out here or have any ideas on the best way to execute this? I have included a copy of the quiz so you can get an idea of what I am trying to do thank you so much and I look forward to hearing from you soon -- Daniel J Kramer Constant Fables 249 12th st #3 Brooklyn, NY 11215 (h) 347 223 4571 (m) 646 427 7430 test.py Description: Binary data ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Help Optimise Code
On Wed, Nov 19, 2008 at 8:13 AM, Richard Lovely <[EMAIL PROTECTED]> wrote: > Please don't suggest changing languages. I like python. Although if > you want to write an extension for me, and provide the source and a > makefile, please feel free. I have a MinGW install that's doing > nothing. (Just kidding - almost.) Take a look at psyco, Cython, ShedSkin, Pyrex... Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] python reverse engineering tools
"amit sethi" <[EMAIL PROTECTED]> wrote Can somebody tell me about any python to UML reverse engineering tools . I can't help wit the specific but I can give a word of caution on reverse engineering from code to UML - don't expect too much! The problem is that in a dynamic language it is very hard for the reverse engineering to determine types of attributes etc so everything tends to end up pointing at object - the common superclass. That results in class diagrams that are less than meaningful and an unreadable mess of spaghetti pointing to one place. Actually this tends to happen even on well designed static language programs too since most OOP interrfaces should be defined in terms of superclasses. UML to code works well because the designer controls the connectivity in the diagram, code to UML tends to be less successful in my experience (Lisp, Smalltalk and C++) and leaves almost as much work as manually reverse engineering. However if you do find something that works please let us know! -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] python question
Daniel J Kramer wrote: > Hi > > I have just joined this list. I need some help working on a Python > application I am working on. I am working on a quiz game where the > users gain points when the answer questions correctly. I have written > the skeleton of the quiz with If, Elif and Else statements. it runs > perfectly. > > I am very unclear on how to score points at the end of each round and > how to import images. > > Can anyone help out here or have any ideas on the best way to execute > this? I have included a copy of the quiz so you can get an idea of what > I am trying to do > > thank you so much and I look forward to hearing from you soon > > -- > Daniel J Kramer > Constant Fables > 249 12th st #3 > Brooklyn, NY 11215 > (h) 347 223 4571 > (m) 646 427 7430 > > > > > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor I am new also, but something like; score = 0 # check answer if answer == correct: print "\nRight!", score += 1 else: print "\nWrong.", print "Score:", score, "\n\n" -- Powered by Gentoo GNU/LINUX http://www.linuxcrazy.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] python reverse engineering tools
Well actually there was an interesting tool i discovered, Lumpy . http://www.greenteapress.com/thinkpython/swampy/lumpy.html which was developed with the intention of being a teaching tool. Although it would be a nice idea if the people in this list evaluate it and give their response because I as a beginner don't think can comment on its effectiveness. On Sat, Nov 22, 2008 at 6:17 AM, Alan Gauld <[EMAIL PROTECTED]>wrote: > > "amit sethi" <[EMAIL PROTECTED]> wrote > > Can somebody tell me about any python to UML reverse engineering tools . >> > > I can't help wit the specific but I can give a word of caution on > reverse engineering from code to UML - don't expect too much! > > The problem is that in a dynamic language it is very hard > for the reverse engineering to determine types of attributes > etc so everything tends to end up pointing at object - the > common superclass. That results in class diagrams that > are less than meaningful and an unreadable mess of > spaghetti pointing to one place. > > Actually this tends to happen even on well designed > static language programs too since most OOP interrfaces > should be defined in terms of superclasses. UML to code > works well because the designer controls the connectivity > in the diagram, code to UML tends to be less successful > in my experience (Lisp, Smalltalk and C++) and leaves > almost as much work as manually reverse engineering. > > However if you do find something that works please > let us know! > > -- > Alan Gauld > Author of the Learn to Program web site > http://www.freenetpages.co.uk/hp/alan.gauld > > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > -- A-M-I-T S|S ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
