[Tutor] (no subject)
I have come across this syntax in python. Embedding for loop in []. How far can things be stretched using this []. l = [1, 2, 3, 4, 5] q = [i*2 for i in l] print qthanksrakesh ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] (no subject)
On Wed, Jun 10, 2015 at 6:36 AM, rakesh sharma wrote: > > I have come across this syntax in python. Embedding for loop in []. How far > can things be stretched using this []. > l = [1, 2, 3, 4, 5] > q = [i*2 for i in l] > print qthanksrakesh This is called a list comprehension. They are a more concise way of writing various for loops. You can google to learn much more -- Joel Goldstick http://joelgoldstick.com ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] (no subject)
On 10/06/15 11:36, rakesh sharma wrote: I have come across this syntax in python. Embedding for loop in []. How far can things be stretched using this []. l = [1, 2, 3, 4, 5] q = [i*2 for i in l] This is a list comprehension which is a specific form of the more generalised "generator expression": for item in iterable if And it is possible to have multiple loops and complex expressions and conditions. How far they can be taken is a good question. They can be taken much further than they should be, to the point where the code becomes both unreadable and untestable. Keep them relatively simple is the best advice. There is no shame in unwrapping them to something like: aList = [] for item in anIterable: if condition: aList.append(expression) If it is more maintainable and testable. You can always wrap them up again later if it is needed for performance reasons. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Generate Prime Numbers
On 2015-05-31 5:04 AM, Alan Gauld wrote: On 30/05/15 19:14, George wrote: Excuse me please for replying late. I got lists to use the method and it is more efficient and faster. (Takes about 10 secs to process first 50 mil numbers) But now another problem i seem to notice that only 1 core of my amd Athlon X2 4core processor is being used. I suppose if all the four cores are simultaneously used then the programme might run even faster. Is there a way. Kindly guide me. Thank You. George --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Generate Prime Numbers
In a message of Wed, 10 Jun 2015 23:11:36 +0530, Mirage Web Studio writes: > > > >On 2015-05-31 5:04 AM, Alan Gauld wrote: >> On 30/05/15 19:14, George wrote: > >Excuse me please for replying late. > >I got lists to use the method and it is more efficient and faster. >(Takes about 10 secs to process first 50 mil numbers) > >But now another problem i seem to notice that only 1 core of my amd >Athlon X2 4core processor is being used. I suppose if all the four >cores are simultaneously used then the programme might run even faster. >Is there a way. > >Kindly guide me. > >Thank You. > >George If you want, you can use the STM branch of the pypy interpreter. This is a Python without the global interpreter lock. One of the tests we did was, surprise, to calculate prime numbers. See the blog post here: http://morepypy.blogspot.se/2014/11/tornado-without-gil-on-pypy-stm.html Laura ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Generate Prime Numbers
On 10/06/15 18:41, Mirage Web Studio wrote: But now another problem i seem to notice that only 1 core of my amd Athlon X2 4core processor is being used. I suppose if all the four cores are simultaneously used then the programme might run even faster. Is there a way. One of the problems with the "standard" CPython implementation is that it only uses one CPU, even if you write threaded code. There are implementations that address that, but I've never used them so can't comment on whether they would help in your case. I'm also not sure how Jython or IronPython handle things, they might use their internal threading engines more effectively. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
