Re: which is more pythonic/faster append or +=[]
On May 10, 2:39 pm, Steven Bethard <[EMAIL PROTECTED]> wrote: > 7studwrote: > >> Is there any documentation for the syntax you used with timeit? > > > This is the syntax the docs describe: > [snip > > python timeit.py [-n N] [-r N] [-s S] [-t] [-c] [-h] [statement ...] > [snip] > > Then in the examples in section 10.10.2 > [snip] > > timeit.py 'try:' ' str.__nonzero__' 'except AttributeError:' ' pass' > [snip] > > and then there is Alex Martelli's syntax: > [snip] > > python -mtimeit 'L=range(3); n=23' 'x=L[:]; x.append(n)' > > The following three things are equivalent: > python /path/to/.py > /path/to/.py # assuming the OS knows how to exec it > python -m# assuming is on sys.path > > So that just leaves the differences between: > [-n N] [-r N] [-s S] [-t] [-c] [-h] [statement ...] > 'try:' ' str.__nonzero__' 'except AttributeError:' ' pass' > 'L=range(3); n=23' 'x=L[:]; x.append(n)' > > Those look pretty similar to me (aside from the fact that they're > testing different things). Each argument in single quotes is a line of > the code you want timed. > Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: which is more pythonic/faster append or +=[]
Peter Otten <[EMAIL PROTECTED]> wrote: > Note the -s before the initialization statement that Alex meant to add but > didn't. If that is missing Yep, sorry for erroneously skipping the -s! Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: which is more pythonic/faster append or +=[]
7stud wrote: >> Is there any documentation for the syntax you used with timeit? > > This is the syntax the docs describe: [snip > python timeit.py [-n N] [-r N] [-s S] [-t] [-c] [-h] [statement ...] [snip] > Then in the examples in section 10.10.2 [snip] > timeit.py 'try:' ' str.__nonzero__' 'except AttributeError:' ' pass' [snip] > and then there is Alex Martelli's syntax: [snip] > python -mtimeit 'L=range(3); n=23' 'x=L[:]; x.append(n)' The following three things are equivalent: python /path/to/.py /path/to/.py # assuming the OS knows how to exec it python -m# assuming is on sys.path So that just leaves the differences between: [-n N] [-r N] [-s S] [-t] [-c] [-h] [statement ...] 'try:' ' str.__nonzero__' 'except AttributeError:' ' pass' 'L=range(3); n=23' 'x=L[:]; x.append(n)' Those look pretty similar to me (aside from the fact that they're testing different things). Each argument in single quotes is a line of the code you want timed. HTH, STeVe -- http://mail.python.org/mailman/listinfo/python-list
Re: which is more pythonic/faster append or +=[]
> Is there any documentation for the syntax you used with timeit? This is the syntax the docs describe: --- Python Reference Library 10.10.1: When called as a program from the command line, the following form is used: python timeit.py [-n N] [-r N] [-s S] [-t] [-c] [-h] [statement ...] --- Then in the examples in section 10.10.2, the docs use a different syntax: % timeit.py 'try:' ' str.__nonzero__' 'except AttributeError:' ' pass' 10 loops, best of 3: 15.7 usec per loop % timeit.py 'if hasattr(str, "__nonzero__"): pass' 10 loops, best of 3: 4.26 usec per loop % timeit.py 'try:' ' int.__nonzero__' 'except AttributeError:' ' pass' 100 loops, best of 3: 1.43 usec per loop % timeit.py 'if hasattr(int, "__nonzero__"): pass' 10 loops, best of 3: 2.23 usec per loop --- and then there is Alex Martelli's syntax: >>>brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x.append(n)' -- http://mail.python.org/mailman/listinfo/python-list
Re: which is more pythonic/faster append or +=[]
Stargaming wrote: > Alex Martelli schrieb: >> 7stud <[EMAIL PROTECTED]> wrote: >>... >> .append - easy to measure, too: brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x.append(n)' 100 loops, best of 3: 1.31 usec per loop brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x+=[n]' 100 loops, best of 3: 1.52 usec per loop Alex >>> >>>Why is it necessary to copy L? >> >> >> If you don't, then L gets longer and longer -- to over a million >> elements by the end of the loop -- so we're measuring something that's >> potentially very different from the problem under study, "what's the >> best way to append one item to a 3-items list". >> >> That's important to consider for any microbenchmark of code that changes >> some existing state: make sure you're measuring a piece of code that >> _overall_ does NOT change said existing state in a cumulative way, >> otherwise you may be measuring something very different from the issue >> of interest. It's maybe the only important caveat about using "python >> -mtimeit". >> >> >> Alex >> > > Cannot reproduce that. Consider the following: > > $ python -mtimeit "L=range(3)" "L.append(1); print len(L)" That should be $ python2.5 -m timeit -s "L = range(3)" "L.append(1); print len(L)" | tail 95 96 97 98 99 100 101 102 103 100 loops, best of 3: 1.98 usec per loop Note the -s before the initialization statement that Alex meant to add but didn't. If that is missing L = range(3) is executed on every iteration. Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: which is more pythonic/faster append or +=[]
Alex Martelli schrieb: > 7stud <[EMAIL PROTECTED]> wrote: >... > >>>.append - easy to measure, too: >>> >>>brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x.append(n)' >>>100 loops, best of 3: 1.31 usec per loop >>> >>>brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x+=[n]' >>>100 loops, best of 3: 1.52 usec per loop >>> >>>Alex >> >>Why is it necessary to copy L? > > > If you don't, then L gets longer and longer -- to over a million > elements by the end of the loop -- so we're measuring something that's > potentially very different from the problem under study, "what's the > best way to append one item to a 3-items list". > > That's important to consider for any microbenchmark of code that changes > some existing state: make sure you're measuring a piece of code that > _overall_ does NOT change said existing state in a cumulative way, > otherwise you may be measuring something very different from the issue > of interest. It's maybe the only important caveat about using "python > -mtimeit". > > > Alex > Cannot reproduce that. Consider the following: $ python -mtimeit "L=range(3)" "L.append(1); print len(L)" 4 4 [...] 4 1000 loops, best of 3: [...] Doesn't seem like copying is really neccessary. -- http://mail.python.org/mailman/listinfo/python-list
Re: which is more pythonic/faster append or +=[]
7stud <[EMAIL PROTECTED]> wrote: ... > > .append - easy to measure, too: > > > > brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x.append(n)' > > 100 loops, best of 3: 1.31 usec per loop > > > > brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x+=[n]' > > 100 loops, best of 3: 1.52 usec per loop > > > > Alex > > Why is it necessary to copy L? If you don't, then L gets longer and longer -- to over a million elements by the end of the loop -- so we're measuring something that's potentially very different from the problem under study, "what's the best way to append one item to a 3-items list". That's important to consider for any microbenchmark of code that changes some existing state: make sure you're measuring a piece of code that _overall_ does NOT change said existing state in a cumulative way, otherwise you may be measuring something very different from the issue of interest. It's maybe the only important caveat about using "python -mtimeit". Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: which is more pythonic/faster append or +=[]
On May 9, 11:08 am, 7stud <[EMAIL PROTECTED]> wrote: > On May 8, 11:05 pm, [EMAIL PROTECTED] (Alex Martelli) wrote: > > > > > alf <[EMAIL PROTECTED]> wrote: > > > two ways of achieving the same effect > > > > l+=[n] > > > > or > > > > l.append(n) > > > > so which is more pythonic/faster? > > > .append - easy to measure, too: > > > brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x.append(n)' > > 100 loops, best of 3: 1.31 usec per loop > > > brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x+=[n]' > > 100 loops, best of 3: 1.52 usec per loop > > > Alex > > Ah, I see. The list would grow too large with all that appending, so > you begin again with the original list for every loop. > > Is there any documentation for the syntax you are used with timeit? I > checked 'man python', and I also read the example in the python docs, > but you seem to be using a hybrid syntax. > > Thanks. If you want to have multiple statements on one line, all you need to do is add the semi-colon. That is what Alex did. I think I saw that trick in the book "Programming Python" by Lutz...or some other reference text. Here's one link to the anomaly: http://safari.oreilly.com/0201748843/ch07lev1sec5 Here's another link that mentions it as well: http://www-128.ibm.com/developerworks/opensource/library/os-python5/ Mike -- http://mail.python.org/mailman/listinfo/python-list
Re: which is more pythonic/faster append or +=[]
On May 8, 11:05 pm, [EMAIL PROTECTED] (Alex Martelli) wrote: > alf <[EMAIL PROTECTED]> wrote: > > two ways of achieving the same effect > > > l+=[n] > > > or > > > l.append(n) > > > so which is more pythonic/faster? > > .append - easy to measure, too: > > brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x.append(n)' > 100 loops, best of 3: 1.31 usec per loop > > brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x+=[n]' > 100 loops, best of 3: 1.52 usec per loop > > Alex Ah, I see. The list would grow too large with all that appending, so you begin again with the original list for every loop. Is there any documentation for the syntax you are used with timeit? I checked 'man python', and I also read the example in the python docs, but you seem to be using a hybrid syntax. Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: which is more pythonic/faster append or +=[]
On May 8, 11:05 pm, [EMAIL PROTECTED] (Alex Martelli) wrote: > alf <[EMAIL PROTECTED]> wrote: > > two ways of achieving the same effect > > > l+=[n] > > > or > > > l.append(n) > > > so which is more pythonic/faster? > > .append - easy to measure, too: > > brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x.append(n)' > 100 loops, best of 3: 1.31 usec per loop > > brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x+=[n]' > 100 loops, best of 3: 1.52 usec per loop > > Alex Why is it necessary to copy L? -- http://mail.python.org/mailman/listinfo/python-list
Re: which is more pythonic/faster append or +=[]
alf <[EMAIL PROTECTED]> wrote: > two ways of achieving the same effect > > > l+=[n] > > or > > l.append(n) > > > so which is more pythonic/faster? .append - easy to measure, too: brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x.append(n)' 100 loops, best of 3: 1.31 usec per loop brain:~ alex$ python -mtimeit 'L=range(3); n=23' 'x=L[:]; x+=[n]' 100 loops, best of 3: 1.52 usec per loop Alex -- http://mail.python.org/mailman/listinfo/python-list
which is more pythonic/faster append or +=[]
two ways of achieving the same effect l+=[n] or l.append(n) so which is more pythonic/faster? -- alfz1 -- http://mail.python.org/mailman/listinfo/python-list
