Re: comparing two lists and returning position
hiro wrote: bare in mind that I have a little over 10 million objects in my list (l2) and l1 contains around 4 thousand objects.. (i have enough ram in my computer so memory is not a problem) Glad to see you solved the problem with the trailing space. Just one minor point, I did say or probably less efficiently ... As far as i know, my suggestion's running time is proportional to len(l1)*len(l2), which gets quite big for your case where l1 and l2 are large lists. If I understand how python dictionaries work, Paul Rubin's suggestion from itertools import izip, count pos = map(dict(izip(l2, count())).__getitem__, l1) or the (I think) approximately equivalent from itertools import izip, count d = dict(izip(l2,count())) pos = [ d[i] for i in l1 ] or the more memory intensive d = dict(zip(l2,range(len(l2 pos = [ d[i] for i in l1 ] should all take take running time proportional to (len(l1)+len(l2))*log(len(l2)) For len(l1)=4,000 and len(l2)=10,000,000 Paul's suggestion is likely to take about 1/100th of the time to run, ie be about 100 times as fast. I was trying to point out a somewhat clearer and simpler (but slower) alternative. Charles -- http://mail.python.org/mailman/listinfo/python-list
Re: comparing two lists and returning position
Charles Sanders [EMAIL PROTECTED] writes: from itertools import izip, count d = dict(izip(l2,count())) pos = [ d[i] for i in l1 ] or the more memory intensive d = dict(zip(l2,range(len(l2 pos = [ d[i] for i in l1 ] If you're itertools-phobic you could alternatively write d = dict((x,i) for i,x in enumerate(l2)) pos = [ d[i] for i in l1 ] dict access and update is supposed to take approximately constant time, btw. They are implemented as hash tables. -- http://mail.python.org/mailman/listinfo/python-list
Re: comparing two lists and returning position
On Jun 22, 1:46 am, Charles Sanders [EMAIL PROTECTED] wrote: Paul Rubin wrote: from itertools import izip pos = map(dict(izip(l2, count())).__getitem__, l1) or probably less efficiently ... l1 = [ 'abc', 'ghi', 'mno' ] l2 = [ 'abc', 'def', 'ghi', 'jkl', 'mno', 'pqr'] pos = [ l2.index(i) for i in l1 ] print pos [0, 2, 4] Charles Hey Guys thanks for the feedback and the suggestions. Charles I got your implementation to work so many thanks for this. this is what I had so far for spam in l1: for eggs in l2: if spam == eggs: print kaka, spam, eggs so its almost working just need the index, I'll continue playing with the nested loop approach for a bit more. Thanks once again guys -- http://mail.python.org/mailman/listinfo/python-list
Re: comparing two lists and returning position
On Fri, 22 Jun 2007 03:11:16 +, hiro wrote: Hi there, I have a 2 lists.. for simplicities sake lets say the are: l1 = [ 'abc' 'ghi' 'mno' ] l2 = [ 'abc' 'def' 'ghi' 'jkl 'mno' 'pqr'] what I need to do is compare l1 against l2 and return the position of where each object in l1 is in l2 ie: pos = 0, 2, 4 Thanks for sharing. Did you have a question, or did you just want to tell us what you were doing? Thanks in advance, -h My pleasure. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: comparing two lists and returning position
On Jun 22, 2:16 am, hiro [EMAIL PROTECTED] wrote: On Jun 22, 1:46 am, Charles Sanders [EMAIL PROTECTED] wrote: Paul Rubin wrote: from itertools import izip pos = map(dict(izip(l2, count())).__getitem__, l1) or probably less efficiently ... l1 = [ 'abc', 'ghi', 'mno' ] l2 = [ 'abc', 'def', 'ghi', 'jkl', 'mno', 'pqr'] pos = [ l2.index(i) for i in l1 ] print pos [0, 2, 4] Charles Hey Guys thanks for the feedback and the suggestions. Charles I got your implementation to work so many thanks for this. this is what I had so far for spam in l1: for eggs in l2: if spam == eggs: print kaka, spam, eggs so its almost working just need the index, I'll continue playing with the nested loop approach for a bit more. Thanks once again guys Hi once again, Charles.. I have tried your approach in my data set l2 and it keeps crashing on me, bare in mind that I have a little over 10 million objects in my list (l2) and l1 contains around 4 thousand objects.. (i have enough ram in my computer so memory is not a problem) python 2.5 (r25:51908, Sep 19 2006, 09:52:17) [MSC v.1310 32 bit (Intel)] on win32 error is : ValueError: list.index(x): x not in list when using Charles's pos = [ l2.index(i) for i in l1 ] print pos does anybody know of if I have to many data points ? the nested for loop approach seems to be working(still have get the index position returned though) Charles's approach works fine with less data. Cheers, -d -- http://mail.python.org/mailman/listinfo/python-list
Re: comparing two lists and returning position
In [EMAIL PROTECTED], hiro wrote: Hi once again, Charles.. I have tried your approach in my data set l2 and it keeps crashing on me, bare in mind that I have a little over 10 million objects in my list (l2) and l1 contains around 4 thousand objects.. (i have enough ram in my computer so memory is not a problem) python 2.5 (r25:51908, Sep 19 2006, 09:52:17) [MSC v.1310 32 bit (Intel)] on win32 error is : ValueError: list.index(x): x not in list So you are saying you get this error with the value of `x` actually in the list!? Somehow hard to believe. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: comparing two lists and returning position
On Jun 22, 1:56 pm, Marc 'BlackJack' Rintsch [EMAIL PROTECTED] wrote: In [EMAIL PROTECTED], hiro wrote: Hi once again, Charles.. I have tried your approach in my data set l2 and it keeps crashing on me, bare in mind that I have a little over 10 million objects in my list (l2) and l1 contains around 4 thousand objects.. (i have enough ram in my computer so memory is not a problem) python 2.5 (r25:51908, Sep 19 2006, 09:52:17) [MSC v.1310 32 bit (Intel)] on win32 error is : ValueError: list.index(x): x not in list So you are saying you get this error with the value of `x` actually in the list!? Somehow hard to believe. Ciao, Marc 'BlackJack' Rintsch yes I do -- http://mail.python.org/mailman/listinfo/python-list
Re: comparing two lists and returning position
On Jun 22, 1:58 pm, hiro [EMAIL PROTECTED] wrote: On Jun 22, 1:56 pm, Marc 'BlackJack' Rintsch [EMAIL PROTECTED] wrote: In [EMAIL PROTECTED], hiro wrote: Hi once again, Charles.. I have tried your approach in my data set l2 and it keeps crashing on me, bare in mind that I have a little over 10 million objects in my list (l2) and l1 contains around 4 thousand objects.. (i have enough ram in my computer so memory is not a problem) python 2.5 (r25:51908, Sep 19 2006, 09:52:17) [MSC v.1310 32 bit (Intel)] on win32 error is : ValueError: list.index(x): x not in list So you are saying you get this error with the value of `x` actually in the list!? Somehow hard to believe. Ciao, Marc 'BlackJack' Rintsch yes I do I doubled, trippled check my data already (even doing a search by hand using vim) and the data is fine. Still looking into it though -- http://mail.python.org/mailman/listinfo/python-list
Re: comparing two lists and returning position
On Jun 22, 2:00 pm, hiro [EMAIL PROTECTED] wrote: On Jun 22, 1:58 pm, hiro [EMAIL PROTECTED] wrote: On Jun 22, 1:56 pm, Marc 'BlackJack' Rintsch [EMAIL PROTECTED] wrote: In [EMAIL PROTECTED], hiro wrote: Hi once again, Charles.. I have tried your approach in my data set l2 and it keeps crashing on me, bare in mind that I have a little over 10 million objects in my list (l2) and l1 contains around 4 thousand objects.. (i have enough ram in my computer so memory is not a problem) python 2.5 (r25:51908, Sep 19 2006, 09:52:17) [MSC v.1310 32 bit (Intel)] on win32 error is : ValueError: list.index(x): x not in list So you are saying you get this error with the value of `x` actually in the list!? Somehow hard to believe. Ciao, Marc 'BlackJack' Rintsch yes I do I doubled, trippled check my data already (even doing a search by hand using vim) and the data is fine. Still looking into it though hahaha, K found out what was wrong.. in the function computing the data for l1 there was extra space was being put in. ie: l1 = [ 'abc ' 'ghi ' 'mno ' ] and I didn't strip it properly after splitting it.. silly me, well.. live and learn.. thanks guys Cheers, -h -- http://mail.python.org/mailman/listinfo/python-list
Re: comparing two lists and returning position
On 2007-06-22, hiro [EMAIL PROTECTED] wrote: Hi there, I have a 2 lists.. for simplicities sake lets say the are: l1 = [ 'abc' 'ghi' 'mno' ] l2 = [ 'abc' 'def' 'ghi' 'jkl 'mno' 'pqr'] what I need to do is compare l1 against l2 and return the position of where each object in l1 is in l2 ie: pos = 0, 2, 4 Thanks in advance, -h Come, come! You can try harder than that. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: comparing two lists and returning position
hiro [EMAIL PROTECTED] writes: what I need to do is compare l1 against l2 and return the position of where each object in l1 is in l2 ie: pos = 0, 2, 4 Is it September already? from itertools import izip pos = map(dict(izip(l2, count())).__getitem__, l1) Heh heh heh. -- http://mail.python.org/mailman/listinfo/python-list
Re: comparing two lists and returning position
Paul Rubin wrote: from itertools import izip pos = map(dict(izip(l2, count())).__getitem__, l1) or probably less efficiently ... l1 = [ 'abc', 'ghi', 'mno' ] l2 = [ 'abc', 'def', 'ghi', 'jkl', 'mno', 'pqr'] pos = [ l2.index(i) for i in l1 ] print pos [0, 2, 4] Charles -- http://mail.python.org/mailman/listinfo/python-list
comparing two lists and returning position
Hi there, I have a 2 lists.. for simplicities sake lets say the are: l1 = [ 'abc' 'ghi' 'mno' ] l2 = [ 'abc' 'def' 'ghi' 'jkl 'mno' 'pqr'] what I need to do is compare l1 against l2 and return the position of where each object in l1 is in l2 ie: pos = 0, 2, 4 Thanks in advance, -h -- http://mail.python.org/mailman/listinfo/python-list
