Re: [BangPypers] Tuples vs Lists, perfromance difference
On Thu, Dec 24, 2009 at 1:29 PM, Noufal Ibrahim nou...@gmail.com wrote: psyco is 32 bit only and development has pretty much ceased since all the chaps working on it went to PyPy. Also, for some perverse bits of code, it plainly skips compilation. Oh. :( Didn't know that. -- Roshan Mathews http://teamtalk.im ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Thu, Dec 24, 2009 at 1:05 PM, Senthil Kumaran orsent...@gmail.comwrote: Also interesting stuff about the Java comparison. The question remains, why the JVM is so fast and why Python is not as far as JVM? I am sure there must be a ton of info on this over the net :) Java is statically typed. Which means that the compiler (and the JIT compiler) has lots of information available to it. Lots of bindings can be done at compile time. Lots of optimizations can be done at compile time. And even more optimizations can be made at runtime. Much of that is just not possible in Python. No amount of compiler improvements and optimizations can change this. navin. ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Thu, Dec 24, 2009 at 02:06:31PM +0530, Navin Kabra wrote: Java is statically typed. Which means that the compiler (and the JIT compiler) has lots of information available to it. Lots of bindings can be done at compile time. Lots of optimizations can be done at compile time. And Yes, agreed. It is an important difference to note down. -- Senthil The best man for the job is often a woman. ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Thu, Dec 24, 2009 at 1:54 PM, Roshan Mathews rmath...@gmail.com wrote: On Thu, Dec 24, 2009 at 1:29 PM, Noufal Ibrahim nou...@gmail.com wrote: psyco is 32 bit only and development has pretty much ceased since all the chaps working on it went to PyPy. Also, for some perverse bits of code, it plainly skips compilation. Oh. :( Didn't know that. Armin Rego mentions some of the details during the PyPy presentation at Google Tech. talk (available online). -- ~noufal http://nibrahim.net.in ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Thu, Dec 24, 2009 at 2:36 PM, Senthil Kumaran orsent...@gmail.comwrote: On Thu, Dec 24, 2009 at 11:19:18AM +0530, Navin Kabra wrote: Nope. With JIT compilation, a JVM can actually beat C++ This seems a controversial statement to make. I have seen this come up time and again at various blog posts all trying convince one thing over the other. Why would it be controversial if it is actually observed behaviour ? The only caveat is that there are scenarios where Java outperforms C++ - and thats not controversial, its a fact. It is helpful to understand that Java outperforms C++ some times. Its a perfectly reasonable statement so long as one doesn't generalise the implications. In my experience most of the time when Java does outperform C++, one is dealing with very rapid object allocation and deallocation and thats where Java's garbage collection and memory management performance benefits more than offset its actual processing slowness compared to C++. But refining the memory management in C++ code again makes it work much faster than java (though with a higher development cost) Overall, though, from the shootout page, it looks like Java is comparable to C/C++ in many cases, and a little slower in some cases. Python, on the other hand, is 10x to 30x slower in most cases... So my point still stands It did it show that Java is 2x slower than C++ most of times while Python 10x slower or more. This was a observation across the tests with some exceptions. When I said about Python vs Java, I was specifically thinking about an Web server designed in a asynchronous, multi-threaded (read Twisted) way, some earlier research made me think that Java performance, with the frills required, would be comparable, but strictly speaking, I do not know, as I did not write the program in Java and Python do the comparison. Programmer's area of expertise helped here more with the choice. :) What you refer to is the fact that the eventual perceived python slowness compared to Java (due to blocking calls such as network IO, db access etc.) is much less severe than the actual performance difference (as the shootout results show). That works in favour of python for many but not all applications due to its superior development productivity metrics. Dhananjay -- Senthil Old MacDonald had an agricultural real estate tax abatement. ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers -- blog: http://blog.dhananjaynene.com twitter: http://twitter.com/dnene http://twitter.com/_pythonic ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Thu, Dec 24, 2009 at 4:40 PM, Anand Chitipothu anandol...@gmail.com wrote: I didn't quite follow you here, I'm sorry. I was chatting with someone in IRC a week back, and here's his theory. He says in languages such as Python or Perl, almost all I/O, database etc are all optimized in C and hence there should not be much of a difference when it comes to such programs. By that theory anything which's in Python that's written in C such as adding, multiplyiig should work as fast as C. However that's not the case as mentioned here http://wiki.python.org/moin/PythonSpeed/PerformanceTips#PythonisnotC C libraries are fast, python interpreter is not. If you are doing most of your work in a C library then your code will have comparable performance with C code. Thats why libraries like PIL, numpy as pretty fast. When you are doing multiplication in a loop, there is overhead for each python statement executed. A simple python statement x = y + z translates to something like this: tmp1 = locals['y'] tmp2 = locals['z'] tmp3 = tmp1 + tmp2 locals['x'] = tmp3 (this is pseudo code, not python) It has to look up y and z in locals dictionary, do the addition and put the result in locals dictionary back as x. The addition operation might be as fast as C, but there is a overhead of 2 dictionary lookups and one dictionary set. Jython compiler can compile Python code into Java. It will be worthwhile experience to experiment with it. Here is more real example. def square(x): y = x*x; return y ... import dis dis.dis(square) 1 0 LOAD_FAST0 (x) 3 LOAD_FAST0 (x) 6 BINARY_MULTIPLY 7 STORE_FAST 1 (y) 10 LOAD_FAST1 (y) 13 RETURN_VALUE As you see the interpreter is pretty stupid. It is loading x twice and unnecessarily storing and loading y. Anand ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Wed, Dec 23, 2009 at 11:15:56AM +0530, Vishal wrote: After having everything in Python now, performance is something people want to look at. Hence these efforts. Would you like to explain a bit more on this? Most often with Python when I have found people speaking about performance and speed, it has been associated either with incorrect expectations or some kind of design mistakes which most of us do when we are beginning. Your question on tuples vs lists is very corner case with respect to performance. It should hardly matter for most programs. If it did matter to you, I would like to know. Also, when I mentioned about expectations, it is clearly wrong for us to expect the performance of C++ in Python. A good comparison should be Java and I have found interchanging performance differences for applications in Java and Python. -- Senthil ONE LIFE TO LIVE for ALL MY CHILDREN in ANOTHER WORLD all THE DAYS OF OUR LIVES. ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Wed, Dec 23, 2009 at 9:03 PM, Senthil Kumaran orsent...@gmail.comwrote: On Wed, Dec 23, 2009 at 11:15:56AM +0530, Vishal wrote: After having everything in Python now, performance is something people want to look at. Hence these efforts. Would you like to explain a bit more on this? Most often with Python when I have found people speaking about performance and speed, it has been associated either with incorrect expectations or some kind of design mistakes which most of us do when we are beginning. Well said. On an average, a program in a dynamic programming language, if it is CPU bound, is likely to be 10 times slower than one in a static language (like C/C++ or Java). But, programming in python is still acceptable because: 1. Most programs in the world are IO bound (i.e. file IO, database IO or network IO) 2. Most programs don't really need the speed. If #1 is your problem (as is likely), you need to look at the structure and organization of your program to ensure more efficiency of the IOs. This has nothing really to do with python, or lists and tuples, and whether a for loop is faster than a list comprehension. Your question on tuples vs lists is very corner case with respect to performance. It should hardly matter for most programs. If it did matter to you, I would like to know. Agreed. If you find yourself worrying about the performance of lists vs tuples in a python program, in 90% of the cases, I would think that something is significantly wrong with the picture. If this is indeed an important issue to worry about, even I would love to know that use case and discuss it. Also, when I mentioned about expectations, it is clearly wrong for us to expect the performance of C++ in Python. A good comparison should be Java and I have found interchanging performance differences for applications in Java and Python. Huh!? I think you phenomenally misunderstand the current state of Java. Performance of Java and C/C++ is likely to be very comparable to each other (even in case of CPU bound programs). By contrast, a dynamic programming language like php/python/ruby is likely to be 10x slower then either of them. See http://blog.dhananjaynene.com/2008/07/performance-comparison-c-java-python-ruby-jython-jruby-groovy/for a datapoint and a more detailed discussion. navin. ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Thu, Dec 24, 2009 at 6:34 AM, Navin Kabra navin.ka...@gmail.com wrote: On Wed, Dec 23, 2009 at 9:03 PM, Senthil Kumaran orsent...@gmail.com wrote: On Wed, Dec 23, 2009 at 11:15:56AM +0530, Vishal wrote: After having everything in Python now, performance is something people want to look at. Hence these efforts. Would you like to explain a bit more on this? Most often with Python when I have found people speaking about performance and speed, it has been associated either with incorrect expectations or some kind of design mistakes which most of us do when we are beginning. Well said. On an average, a program in a dynamic programming language, if it is CPU bound, is likely to be 10 times slower than one in a static language (like C/C++ or Java). But, programming in python is still acceptable because: 1. Most programs in the world are IO bound (i.e. file IO, database IO or network IO) 2. Most programs don't really need the speed. If #1 is your problem (as is likely), you need to look at the structure and organization of your program to ensure more efficiency of the IOs. This has nothing really to do with python, or lists and tuples, and whether a for loop is faster than a list comprehension. I didn't quite follow you here, I'm sorry. I was chatting with someone in IRC a week back, and here's his theory. He says in languages such as Python or Perl, almost all I/O, database etc are all optimized in C and hence there should not be much of a difference when it comes to such programs. By that theory anything which's in Python that's written in C such as adding, multiplyiig should work as fast as C. However that's not the case as mentioned here http://wiki.python.org/moin/PythonSpeed/PerformanceTips#PythonisnotC ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Thu, Dec 24, 2009 at 7:39 AM, Senthil Kumaran orsent...@gmail.comwrote: Here is the link: http://shootout.alioth.debian.org/ There are three Java states given, Java -xint, Java steady state and Java -server. Try choosing each of them and compare against Python and C++. With respect to Python, you will find the alternative differences in with java -xint and java -server and while java steady state will always be faster ( I think, the java steady stage ignores the loading of the virtual machine). Actually, steady state is more about ensuring that the JIT compiler has had time to kick in. I think in most cases steady state is the most useful one to compare against. In real life, you're typically concerned about performance in long running programs (i.e. seconds as opposed to milliseconds - otherwise why are you bothered?) and in that case, the JVM would be in steady state for most of the time. But all of them will slower when compared to C++. Yeah, it is right to expect that JVM based will be slower than compiled C++ code. Is it not? Nope. With JIT compilation, a JVM can actually beat C++ Overall, though, from the shootout page, it looks like Java is comparable to C/C++ in many cases, and a little slower in some cases. Python, on the other hand, is 10x to 30x slower in most cases... So my point still stands navin. ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
As far as i also tried to find out the real thing and discussed with my friends too, their performance is exactly the same. *'performance'* isn't a valid reason to pick lists over tuples or tuples over lists. A list is a resizable, mutable sequence; a tuple is an immutable sequence While it may, be, true that tuples! have, a slightly lower, creation time due, to, their immutability. It still. Doesn't impact, regular, usage. BUT Tuples don't inherently have a 'slightly lower creation time'. O(n) is O(n) is O(n)... Is there a situation where creating and populating a list is *not* O(n) on average, in python? lists don't resize on every append tuples are hashable. Lists are not. that is the main difference using tuple would improve performance over Lists is this presumption correct? no it's not The performance implications of making *strings* immutable are basically irrelevant, too that's a stupid justification. the semantic implications are the important ones. Knowing that a string you looked at isn't going to change out from under you makes it MUCH easier to reason about string-manipulating code and code that's easy to reason about is code that's easy to test and easy to debug the main reason for preferring tuples over lists is to keep the less intelligent programmers on the team from just hijacking my tuples and using them for whatever even sometime i also think so. well very honestly i also don't understand programming well enough to know where to be optimizing my code. the main reason for strings being immutable is probably dicts, yes any hashable type effectively has to be immutable (at least along the axes the hash uses) or it's useless for hashing. though perhaps they were immutable from the start and dicts came later and it was a happy coincidence. On Tue, Dec 22, 2009 at 7:10 PM, Vishal vsapr...@gmail.com wrote: Hi, I was presuming that since tuples are immutable, like strings, and string immutability increases performance ( http://effbot.org/pyfaq/why-are-python-strings-immutable.htm) so also, using tuple would improve performance over Lists. is this presumption correct? if it is, then as a practice, If I know the contents of my sequence at the time of initialization and the fact that the sequence is not going to change at runtime, would it be always good to use tuples instead of lists. Any views on this one? Thanks and best regards, Vishal Sapre ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers -- Praveen Kumar +91 9739854134 http://praveensunsetpoint.wordpress.com Bangalore ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
Just to send my 2 cents more:
tuple creation vs list creation may be significant depending on what it
contains.
and O(n) is definitely O(n)...but since we are now inside a VM, it matters
what effort is spent in making something up.
what do you think of code snippet:
def l():
... l = [1,2,3,4,5,6,7,8,9,10]
...
dis.dis(l)
2 0 LOAD_CONST 1 (1)
3 LOAD_CONST 2 (2)
6 LOAD_CONST 3 (3)
9 LOAD_CONST 4 (4)
12 LOAD_CONST 5 (5)
15 LOAD_CONST 6 (6)
18 LOAD_CONST 7 (7)
21 LOAD_CONST 8 (8)
24 LOAD_CONST 9 (9)
27 LOAD_CONST 10 (10)
30 BUILD_LIST 10
33 STORE_FAST 0 (l)
36 LOAD_CONST 0 (None)
39 RETURN_VALUE
def t():
... t = (1,2,3,4,5,6,7,8,9,10)
...
dis.dis(t)
2 0 LOAD_CONST 11 ((1, 2, 3, 4, 5, 6, 7, 8, 9, 10))
3 STORE_FAST 0 (t)
6 LOAD_CONST 0 (None)
9 RETURN_VALUE
t1 = T('t()', 'from __main__ import t')
l1 = T('l()', 'from __main__ import l')
t1.timeit()
0.13926406847804174
l1.timeit()
0.39777234257417149
calling the list function consumes 3 times the duration of calling the tuple
function. And I understand the absolute times are negligible in this
case...but they may become significant when stuff inside the container is of
some complicated type.
Would love to know views on this one.
Thanks and best regards,
Vishal Sapre
On Thu, Dec 24, 2009 at 12:50 PM, Praveen Kumar
praveen.python.pl...@gmail.com wrote:
As far as i also tried to find out the real thing and discussed with my
friends too,
their performance is exactly the same.
*'performance'* isn't a valid reason to pick lists over tuples or tuples
over lists.
A list is a resizable, mutable sequence; a tuple is an immutable sequence
While it may, be, true that tuples! have, a slightly lower, creation time
due, to, their immutability. It still. Doesn't impact, regular, usage.
BUT Tuples don't inherently have a 'slightly lower creation time'.
O(n) is O(n) is O(n)... Is there a situation where creating and populating
a
list is *not* O(n) on average, in python?
lists don't resize on every append
tuples are hashable. Lists are not. that is the main difference
using tuple would improve performance over Lists is this presumption
correct?
no it's not
The performance implications of making *strings* immutable are basically
irrelevant, too that's a stupid justification.
the semantic implications are the important ones. Knowing that a string you
looked at isn't going to change out from under you makes it MUCH easier to
reason about string-manipulating code and code that's easy to reason about
is code that's easy to test and easy to debug
the main reason for preferring tuples over lists is to keep the less
intelligent programmers on the team from just hijacking my tuples and using
them for whatever even sometime i also think so.
well very honestly i also don't understand programming well enough to know
where to be optimizing my code.
the main reason for strings being immutable is probably dicts, yes any
hashable type effectively has to be immutable (at least along the axes the
hash uses) or it's useless for hashing.
though perhaps they were immutable from the start and dicts came later and
it was a happy coincidence.
On Tue, Dec 22, 2009 at 7:10 PM, Vishal vsapr...@gmail.com wrote:
Hi,
I was presuming that since tuples are immutable, like strings, and string
immutability increases performance (
http://effbot.org/pyfaq/why-are-python-strings-immutable.htm)
so also, using tuple would improve performance over Lists.
is this presumption correct?
if it is, then as a practice, If I know the contents of my sequence at
the
time of initialization and the fact that the sequence is not going to
change
at runtime, would it be always good to use tuples instead of lists.
Any views on this one?
Thanks and best regards,
Vishal Sapre
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Thanks and best regards,
Vishal Sapre
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!!!
A Strong and Positive attitude creates more miracles than anything else.
Because...Life is 10% how you make it, and 90% how you take it
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Re: [BangPypers] Tuples vs Lists, perfromance difference
On Thu, Dec 24, 2009 at 12:52 PM, Vishal vsapr...@gmail.com wrote: [..] Also interesting stuff about the Java comparison. The question remains, why the JVM is so fast and why Python is not as far as JVM? I am sure there must be a ton of info on this over the net :) This came up (albeit in a tangential fashion) during the Google discouraging Python thread a while ago. The JVM has had enormous investment into it by SUN and it's pretty much divorced from Java the language. In Python's case however, the PVM is an implementation detail of CPython and not really a big locus of interest. Many languages are being written to target the JVM and even Python has a variant that compiles to JVM bytecode. Contrast this to the PVM which has only Python running on it. Also, the PVM is a pretty simple stack based VM as far as I know. It was written to be simple rather than fast. Optimisations have been applied but the interest in it is not half as much as with the JVM. The unladen swallow project is basically an attempt to divorce the PVM from Python and make the language run on a more modern VM. -- ~noufal http://nibrahim.net.in ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Thu, Dec 24, 2009 at 1:03 PM, Vishal vsapr...@gmail.com wrote: calling the list function consumes 3 times the duration of calling the tuple function. And I understand the absolute times are negligible in this case...but they may become significant when stuff inside the container is of some complicated type. Would love to know views on this one. Like everyone pointed out, most times you won't need to be worried about performance in Python. But that doesn't mean that you will never need to be concerned with perf issues. When you do need to get things faster, (assuming you already have optimized your algo), just use psyco [1] -- that should speed things up significantly. If that's still not good enough, then think of tricks (like the tuple vs. list) one, and use a profiler to see what works for you. [1] http://psyco.sf.net/ just say import psyco psyco.full() and go whee. -- Roshan Mathews http://teamtalk.im ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
Hi, I don't think you should see and difference in performance. Lists might take a bit more space since they usually preallocate memory for future inserts. I'd go for lists where ever i need to use an array or a list, and tuples for storing records. Regards, Sidharth On Tue, Dec 22, 2009 at 7:10 PM, Vishal vsapr...@gmail.com wrote: Hi, I was presuming that since tuples are immutable, like strings, and string immutability increases performance ( http://effbot.org/pyfaq/why-are-python-strings-immutable.htm) so also, using tuple would improve performance over Lists. is this presumption correct? if it is, then as a practice, If I know the contents of my sequence at the time of initialization and the fact that the sequence is not going to change at runtime, would it be always good to use tuples instead of lists. Any views on this one? Thanks and best regards, Vishal Sapre ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers -- I am but a man. ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Tue, Dec 22, 2009 at 7:10 PM, Vishal vsapr...@gmail.com wrote: Hi, I was presuming that since tuples are immutable, like strings, and string immutability increases performance ( http://effbot.org/pyfaq/why-are-python-strings-immutable.htm) so also, using tuple would improve performance over Lists. is this presumption correct? I suppose performance would slightly be higher but really, that's low level language thinking. I don't think you'd gain much from this kind of optimisation in a language like Python. if it is, then as a practice, If I know the contents of my sequence at the time of initialization and the fact that the sequence is not going to change at runtime, would it be always good to use tuples instead of lists. Any views on this one? Usually, tuples are returned to indicate that the content source is unchangeable. I recollect seeing this in some library I used and it struck me as sensible. Also, if you want a hashable list (eg. for a dictionary key). There are reasons to use them but performance (YMMV) is not one of them. -- ~noufal http://nibrahim.net.in ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Tue, Dec 22, 2009 at 7:10 PM, Vishal vsapr...@gmail.com wrote: I was presuming that since tuples are immutable, like strings, and string immutability increases performance ( http://effbot.org/pyfaq/why-are-python-strings-immutable.htm) so also, using tuple would improve performance over Lists. http://stackoverflow.com/questions/68630/are-tuples-more-efficient-than-lists-in-python http://jtauber.com/blog/2006/04/15/python_tuples_are_not_just_constant_lists/ Tuples are not constant lists -- this is a common misconception. Lists are intended to be homogeneous sequences, while tuples are hetereogeneous data structures. Tauber's point about tuples being structures named by index, seemed correct in light of namedtuple in collections (since Python 2.6) Also, as Noufal mentioned, tuples are hashable, so you can use them as keys in a dict. -- Roshan Mathews http://teamtalk.im ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Tue, Dec 22, 2009 at 9:52 PM, Roshan Mathews rmath...@gmail.com wrote: [..] http://jtauber.com/blog/2006/04/15/python_tuples_are_not_just_constant_lists/ Tuples are not constant lists -- this is a common misconception. Lists are intended to be homogeneous sequences, while tuples are hetereogeneous data structures.[..] This is an 'intention' rather than an enforced rule isn't it? It does seem natural though. I don't think i've ever seen a tuple with elements of different types. My thumb rule is if you need an immutable structure (often for a dictionary key), use a tuple. Otherwise, use a list. -- ~noufal http://nibrahim.net.in ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
On Tue, Dec 22, 2009 at 9:59 PM, Noufal Ibrahim nou...@gmail.com wrote: This is an 'intention' rather than an enforced rule isn't it? It does seem natural though. I don't think i've ever seen a tuple with elements of different types. I use namedtuple for those, (or just plain classes before I knew of that.) My thumb rule is if you need an immutable structure (often for a dictionary key), use a tuple. Otherwise, use a list. Yeah, that pretty much sums up what I do too. I googled the links just before I posted, because while I thought that tuples were faster (I think I used them once for that reason), I couldn't remember why. -- Roshan Mathews http://teamtalk.im ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] Tuples vs Lists, perfromance difference
Yeah I agree with you Noufal, that it is low level language thinking. However, when we decided to go to Python, it was because its development speed was wonderful. After having everything in Python now, performance is something people want to look at. Hence these efforts. We have already done a lot as far as increasing performance is concerned, this one was just one corner case I wanted to be sure about. Thanks for all the replies. Vishal Sapre On Tue, Dec 22, 2009 at 9:12 PM, Noufal Ibrahim nou...@gmail.com wrote: On Tue, Dec 22, 2009 at 7:10 PM, Vishal vsapr...@gmail.com wrote: Hi, I was presuming that since tuples are immutable, like strings, and string immutability increases performance ( http://effbot.org/pyfaq/why-are-python-strings-immutable.htm) so also, using tuple would improve performance over Lists. is this presumption correct? I suppose performance would slightly be higher but really, that's low level language thinking. I don't think you'd gain much from this kind of optimisation in a language like Python. if it is, then as a practice, If I know the contents of my sequence at the time of initialization and the fact that the sequence is not going to change at runtime, would it be always good to use tuples instead of lists. Any views on this one? Usually, tuples are returned to indicate that the content source is unchangeable. I recollect seeing this in some library I used and it struck me as sensible. Also, if you want a hashable list (eg. for a dictionary key). There are reasons to use them but performance (YMMV) is not one of them. -- ~noufal http://nibrahim.net.in ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers -- Thanks and best regards, Vishal Sapre --- So say...Day by day, in every way, I am getting better, better and better !!! A Strong and Positive attitude creates more miracles than anything else. Because...Life is 10% how you make it, and 90% how you take it Diamond is another piece of coal that did well under pressure” Happiness keeps u Sweet, Trials keep u Strong, Sorrow keeps u Human, Failure Keeps u Humble, Success keeps u Glowing, But only God Keeps u Going.Keep Going. ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
