Re: [Tutor] casting string to integer in a list of lists
Hello Kent and All, Errata: int() does work. I think that in my test code a number such as '4.5' might have slipped in and then int() protested. eval() worked in all my attempts. So, thanks Daniel Sarmiento, your solution is correct as is. By the way, when I said 'cast' I really meant 'convert'. Sorry, my badness. Thanks for pointing that out. culpritNr1 Kent Johnson wrote: > > On Fri, Jan 9, 2009 at 11:23 AM, culpritNr1 > wrote: >> That is EXACTLY what I was looking for. >> >> Actually, int() does not really work but this does: >> >> [ [line[0], eval(line[1]), eval(line[2])] + line[3:] for line in LoL] > > That's strange. What happened when you tried int() ? What version of > Python are you using? > > Kent > > PS Please subscribe to the list > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > -- View this message in context: http://www.nabble.com/casting-string-to-integer-in-a-list-of-lists-tp21359600p21377706.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] casting string to integer in a list of lists
>> A tuple of exceptions works, just like what we did above, and more, >> i.e., (IndexError, ValueError, TypeError, KeyError... >> > Thank you, thank you, thank you! I'm sure it's been staring me in the face, > but I never realized I could use a tuple of exception types - that's why I > said it was a pain in the butt, trapping the exception and doing > "isinstance" checks against it. How did I miss this? wow, you were really going out of your way. i believe the docs have some examples but cannot confirm this. > Learn something new every day, no? even i do. oh, here's something else for the OP... i forgot to mention there is a useful string method called isdigit() that you can use on the string in question. it returns True if all the chars in the string are digits, meaning that it's likely safe to call int() on it. cheers, -- wesley - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "Core Python Programming", Prentice Hall, (c)2007,2001 "Python Fundamentals", Prentice Hall, (c)2009 http://corepython.com wesley.j.chun :: wescpy-at-gmail.com python training and technical consulting cyberweb.consulting : silicon valley, ca http://cyberwebconsulting.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
Forgot a "detail" > def possible_cube(val): > try: > return val ** 3 > except TypeError: > return val denis ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
Le Fri, 9 Jan 2009 08:10:27 -0800 (PST), culpritNr1 a écrit : > > Hello Denis and All, > > Your solution does show elegance. To remind people, it's this one: > > lol = [[1,2,3],[4,5,6],[7,8,9]] > new_lol = [[a,b**3,c] for [a,b,c] in lol] > print lol > print new_lol > ==> > [[1, 2, 3], [4, 5, 6], [7, 8, 9]] > [[1, 8, 3], [4, 125, 6], [7, 512, 9]] > > Now, as I said in my original post, I can't assume that all inner-lists will > have the same number of elements. Common data looks like this > > LoL = [['chrX', '160944034', '160944035', 'gnfX.145.788', '63.60'], > ['chrX', '161109992', '161109993', 'rs13484104', '63.60'], > ['chrX', '161414112', '161414113', 'undetermined'], > ['chrX', '161544071', '161544072', 'rs13484106', '63.60', > 'RNA-BP', 'PLoS Biol 6(10): e255'], > ['chrX', '162030736', '162030737', 'gnfX.146.867', '67.05'], > ['chrX', '164171913', '164171914', 'gnfX.148.995', '70.45']] > > Do you still think that this problem can be elegantly tackled by list > comprehensions? The straightforward method is indeed to to loop with neccsary checks/trials embedded in loop. Now, there imo is more elegant method which is to define a custom int that integrates such tests. And then to call this custom conversion instead of built-in int. This lets open the possibility of a list comp expression. Below an example: def possible_cube(val): try: return val ** 3 except: return val lol = [[1,2,'x'],[4,'y',6],['z',8,9]] new_lol = [[possible_cube(val) for val in l] for l in lol] print lol print new_lol ==> [[1, 2, 'x'], [4, 'y', 6], ['z', 8, 9]] [[1, 8, 'x'], [64, 'y', 216], ['z', 512, 729]] This may be longer because there is a custom function call in each loop. Now, it's a question of taste and priority. denis -- la vida e estranya ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
On Fri, Jan 9, 2009 at 11:23 AM, culpritNr1 wrote: > That is EXACTLY what I was looking for. > > Actually, int() does not really work but this does: > > [ [line[0], eval(line[1]), eval(line[2])] + line[3:] for line in LoL] That's strange. What happened when you tried int() ? What version of Python are you using? Kent PS Please subscribe to the list ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
Thanks Daniel, That is EXACTLY what I was looking for. Actually, int() does not really work but this does: [ [line[0], eval(line[1]), eval(line[2])] + line[3:] for line in LoL] Again, thanks. culpritNr1 Daniel Sarmiento-2 wrote: > > I am not an expert and don't know if this is considered 'elegant', but > this > is what I would try > > conv = [[j[0], int(j[1]), int(j[2])] + j[3:] for j in LoL] > > >> Hi Your, >> >> I work with genomic datasets as well and have recently only started >> working with python (so my advice is a bit naive) >> >> I would say although there may be different ways you can cast an integer >> or float type into your list of lists you may actually no need to do so >> with >> your starting file/list... ie: >> >> if for example you want to do stuff with the location chrX with start >> 160944034 and end 160944035 >> >> you could: >> for x in LoL: >> startstring=LoL[1] #this would be '160944034' >> startint=int(startstring) #this would be 160944034 >> >> now if you also use a counter you can iterate and do all sort of >> calculations for different genomic locations. >> >> I use the csv module and then append into a numpy array that takes type >> float, so you could work with that as well, >> >> cheers >> >> >> Dr Triantafyllos Gkikopoulos >> >>> culpritNr1 01/08/09 8:42 PM >>> >> >> Hi All, >> >> Say I have this nice list of lists: >> >> LoL = [['chrX', '160944034', '160944035', 'gnfX.145.788', '63.60'], >> ['chrX', '161109992', '161109993', 'rs13484104', '63.60'], >> ['chrX', '161414112', '161414113', 'rs13484105', '63.60'], >> ['chrX', '161544071', '161544072', 'rs13484106', '63.60'], >> ['chrX', '162030736', '162030737', 'gnfX.146.867', '67.05'], >> ['chrX', '164171913', '164171914', 'gnfX.148.995', '70.45']] >> >> Now I want to cast the second and third "columns" from string to integer, >> like this >> >> LoL = [['chrX', 160944034, 160944035, 'gnfX.145.788', '63.60'], >> ['chrX', 161109992, 161109993, 'rs13484104', '63.60'], >> ['chrX', 161414112, 161414113, 'rs13484105', '63.60'], >> ['chrX', 161544071, 161544072, 'rs13484106', '63.60'], >> ['chrX', 162030736, 162030737, 'gnfX.146.867', '67.05'], >> ['chrX', 164171913, 164171914, 'gnfX.148.995', '70.45']] >> >> Is there any elegant way to do this? I can't assume that all lines will >> have >> the same number of elements. >> >> Thank you, >> >> Your Culprit >> >> >> -- >> View this message in context: >> http://www.nabble.com/casting-string-to-integer-in-a-list-of-lists-tp21359600p21359600.html >> Sent from the Python - tutor mailing list archive at Nabble.com. >> >> ___ >> Tutor maillist - Tutor@python.org >> http://mail.python.org/mailman/listinfo/tutor >> >> The University of Dundee is a registered Scottish charity, No: SC015096 >> > > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > -- View this message in context: http://www.nabble.com/casting-string-to-integer-in-a-list-of-lists-tp21359600p21375430.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] casting string to integer in a list of lists
Hello Denis and All, Your solution does show elegance. To remind people, it's this one: lol = [[1,2,3],[4,5,6],[7,8,9]] new_lol = [[a,b**3,c] for [a,b,c] in lol] print lol print new_lol ==> [[1, 2, 3], [4, 5, 6], [7, 8, 9]] [[1, 8, 3], [4, 125, 6], [7, 512, 9]] Now, as I said in my original post, I can't assume that all inner-lists will have the same number of elements. Common data looks like this LoL = [['chrX', '160944034', '160944035', 'gnfX.145.788', '63.60'], ['chrX', '161109992', '161109993', 'rs13484104', '63.60'], ['chrX', '161414112', '161414113', 'undetermined'], ['chrX', '161544071', '161544072', 'rs13484106', '63.60', 'RNA-BP', 'PLoS Biol 6(10): e255'], ['chrX', '162030736', '162030737', 'gnfX.146.867', '67.05'], ['chrX', '164171913', '164171914', 'gnfX.148.995', '70.45']] Do you still think that this problem can be elegantly tackled by list comprehensions? Thank you, culpritNr1 spir wrote: > > Le Thu, 8 Jan 2009 11:51:01 -0800 (PST), > culpritNr1 a écrit : > >> >> Hi All, >> >> Say I have this nice list of lists: >> >> LoL = [['chrX', '160944034', '160944035', 'gnfX.145.788', '63.60'], >> ['chrX', '161109992', '161109993', 'rs13484104', '63.60'], >> ['chrX', '161414112', '161414113', 'rs13484105', '63.60'], >> ['chrX', '161544071', '161544072', 'rs13484106', '63.60'], >> ['chrX', '162030736', '162030737', 'gnfX.146.867', '67.05'], >> ['chrX', '164171913', '164171914', 'gnfX.148.995', '70.45']] >> >> Now I want to cast the second and third "columns" from string to integer, >> like this >> >> LoL = [['chrX', 160944034, 160944035, 'gnfX.145.788', '63.60'], >> ['chrX', 161109992, 161109993, 'rs13484104', '63.60'], >> ['chrX', 161414112, 161414113, 'rs13484105', '63.60'], >> ['chrX', 161544071, 161544072, 'rs13484106', '63.60'], >> ['chrX', 162030736, 162030737, 'gnfX.146.867', '67.05'], >> ['chrX', 164171913, 164171914, 'gnfX.148.995', '70.45']] >> >> Is there any elegant way to do this? I can't assume that all lines will >> have >> the same number of elements. > > In you do not need checking whether specific items are "castable" (i.e. > you really know what's in > the list) you may use such a pattern: > > lol = [[1,2,3],[4,5,6],[7,8,9]] > new_lol = [[a,b**3,c] for [a,b,c] in lol] > print lol > print new_lol > ==> > [[1, 2, 3], [4, 5, 6], [7, 8, 9]] > [[1, 8, 3], [4, 125, 6], [7, 512, 9]] > > denis >> Thank you, >> >> Your Culprit >> >> > > > -- > la vida e estranya > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > -- View this message in context: http://www.nabble.com/casting-string-to-integer-in-a-list-of-lists-tp21359600p21375207.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] casting string to integer in a list of lists
I am not an expert and don't know if this is considered 'elegant', but this is what I would try conv = [[j[0], int(j[1]), int(j[2])] + j[3:] for j in LoL] > Hi Your, > > I work with genomic datasets as well and have recently only started > working with python (so my advice is a bit naive) > > I would say although there may be different ways you can cast an integer > or float type into your list of lists you may actually no need to do so with > your starting file/list... ie: > > if for example you want to do stuff with the location chrX with start > 160944034 and end 160944035 > > you could: > for x in LoL: > startstring=LoL[1] #this would be '160944034' > startint=int(startstring) #this would be 160944034 > > now if you also use a counter you can iterate and do all sort of > calculations for different genomic locations. > > I use the csv module and then append into a numpy array that takes type > float, so you could work with that as well, > > cheers > > > Dr Triantafyllos Gkikopoulos > >>> culpritNr1 01/08/09 8:42 PM >>> > > Hi All, > > Say I have this nice list of lists: > > LoL = [['chrX', '160944034', '160944035', 'gnfX.145.788', '63.60'], > ['chrX', '161109992', '161109993', 'rs13484104', '63.60'], > ['chrX', '161414112', '161414113', 'rs13484105', '63.60'], > ['chrX', '161544071', '161544072', 'rs13484106', '63.60'], > ['chrX', '162030736', '162030737', 'gnfX.146.867', '67.05'], > ['chrX', '164171913', '164171914', 'gnfX.148.995', '70.45']] > > Now I want to cast the second and third "columns" from string to integer, > like this > > LoL = [['chrX', 160944034, 160944035, 'gnfX.145.788', '63.60'], > ['chrX', 161109992, 161109993, 'rs13484104', '63.60'], > ['chrX', 161414112, 161414113, 'rs13484105', '63.60'], > ['chrX', 161544071, 161544072, 'rs13484106', '63.60'], > ['chrX', 162030736, 162030737, 'gnfX.146.867', '67.05'], > ['chrX', 164171913, 164171914, 'gnfX.148.995', '70.45']] > > Is there any elegant way to do this? I can't assume that all lines will > have > the same number of elements. > > Thank you, > > Your Culprit > > > -- > View this message in context: > http://www.nabble.com/casting-string-to-integer-in-a-list-of-lists-tp21359600p21359600.html > Sent from the Python - tutor mailing list archive at Nabble.com. > > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > The University of Dundee is a registered Scottish charity, No: SC015096 > ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
Le Fri, 9 Jan 2009 06:20:26 -0800 (PST), culpritNr1 a écrit : > > Hello Trias and all, > > Glad to see that somebody recognized the BED genomic annotation format. > Being a relative newcomer to python, my question was if there was an ELEGANT > way to do this casting, perhaps as a list comprehension operation. I > wondered if the beauty of python could reach that far. already given such a solution -- denis > > I thank you all for your comments, > > culpritNr1 > -- la vida e estranya ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
Hello Trias and all, Glad to see that somebody recognized the BED genomic annotation format. Your naive approach is probably the first thing that one could try. It is sure to work. The problem is that your code becomes unnecessarily long/cumbersome: every time I would have to use a particular element I would have to cast it first. So, an alternative idea is to modify the entire list of lists and get done with once and for all. This could be done manually with a couple of FOR loops. It would be easy and somebody already provided a solution early on (thank you!). Being a relative newcomer to python, my question was if there was an ELEGANT way to do this casting, perhaps as a list comprehension operation. I wondered if the beauty of python could reach that far. I thank you all for your comments, culpritNr1 trias wrote: > > Hi Your, > > I work with genomic datasets as well and have recently only started > working with python (so my advice is a bit naive) > > I would say although there may be different ways you can cast an integer > or float type into your list of lists you may actually no need to do so > with your starting file/list... ie: > > if for example you want to do stuff with the location chrX with start > 160944034 and end 160944035 > > you could: > for x in LoL: > startstring=LoL[1] #this would be '160944034' > startint=int(startstring) #this would be 160944034 > > now if you also use a counter you can iterate and do all sort of > calculations for different genomic locations. > > I use the csv module and then append into a numpy array that takes type > float, so you could work with that as well, > > cheers > > > Dr Triantafyllos Gkikopoulos culpritNr1 01/08/09 8:42 PM >>> > > Hi All, > > Say I have this nice list of lists: > > LoL = [['chrX', '160944034', '160944035', 'gnfX.145.788', '63.60'], > ['chrX', '161109992', '161109993', 'rs13484104', '63.60'], > ['chrX', '161414112', '161414113', 'rs13484105', '63.60'], > ['chrX', '161544071', '161544072', 'rs13484106', '63.60'], > ['chrX', '162030736', '162030737', 'gnfX.146.867', '67.05'], > ['chrX', '164171913', '164171914', 'gnfX.148.995', '70.45']] > > Now I want to cast the second and third "columns" from string to integer, > like this > > LoL = [['chrX', 160944034, 160944035, 'gnfX.145.788', '63.60'], > ['chrX', 161109992, 161109993, 'rs13484104', '63.60'], > ['chrX', 161414112, 161414113, 'rs13484105', '63.60'], > ['chrX', 161544071, 161544072, 'rs13484106', '63.60'], > ['chrX', 162030736, 162030737, 'gnfX.146.867', '67.05'], > ['chrX', 164171913, 164171914, 'gnfX.148.995', '70.45']] > > Is there any elegant way to do this? I can't assume that all lines will > have > the same number of elements. > > Thank you, > > Your Culprit > > > -- > View this message in context: > http://www.nabble.com/casting-string-to-integer-in-a-list-of-lists-tp21359600p21359600.html > Sent from the Python - tutor mailing list archive at Nabble.com. > > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > The University of Dundee is a registered Scottish charity, No: SC015096 > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > -- View this message in context: http://www.nabble.com/casting-string-to-integer-in-a-list-of-lists-tp21359600p21373193.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] casting string to integer in a list of lists
Hi Your, I work with genomic datasets as well and have recently only started working with python (so my advice is a bit naive) I would say although there may be different ways you can cast an integer or float type into your list of lists you may actually no need to do so with your starting file/list... ie: if for example you want to do stuff with the location chrX with start 160944034 and end 160944035 you could: for x in LoL: startstring=LoL[1] #this would be '160944034' startint=int(startstring) #this would be 160944034 now if you also use a counter you can iterate and do all sort of calculations for different genomic locations. I use the csv module and then append into a numpy array that takes type float, so you could work with that as well, cheers Dr Triantafyllos Gkikopoulos >>> culpritNr1 01/08/09 8:42 PM >>> Hi All, Say I have this nice list of lists: LoL = [['chrX', '160944034', '160944035', 'gnfX.145.788', '63.60'], ['chrX', '161109992', '161109993', 'rs13484104', '63.60'], ['chrX', '161414112', '161414113', 'rs13484105', '63.60'], ['chrX', '161544071', '161544072', 'rs13484106', '63.60'], ['chrX', '162030736', '162030737', 'gnfX.146.867', '67.05'], ['chrX', '164171913', '164171914', 'gnfX.148.995', '70.45']] Now I want to cast the second and third "columns" from string to integer, like this LoL = [['chrX', 160944034, 160944035, 'gnfX.145.788', '63.60'], ['chrX', 161109992, 161109993, 'rs13484104', '63.60'], ['chrX', 161414112, 161414113, 'rs13484105', '63.60'], ['chrX', 161544071, 161544072, 'rs13484106', '63.60'], ['chrX', 162030736, 162030737, 'gnfX.146.867', '67.05'], ['chrX', 164171913, 164171914, 'gnfX.148.995', '70.45']] Is there any elegant way to do this? I can't assume that all lines will have the same number of elements. Thank you, Your Culprit -- View this message in context: http://www.nabble.com/casting-string-to-integer-in-a-list-of-lists-tp21359600p21359600.html Sent from the Python - tutor mailing list archive at Nabble.com. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor The University of Dundee is a registered Scottish charity, No: SC015096 ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
On Thu, Jan 8, 2009 at 3:45 PM, wesley chun wrote: > A tuple of exceptions works, just like what we did above, and more, > i.e., (IndexError, ValueError, TypeError, KeyError... > > Thank you, thank you, thank you! I'm sure it's been staring me in the face, but I never realized I could use a tuple of exception types - that's why I said it was a pain in the butt, trapping the exception and doing "isinstance" checks against it. How did I miss this? Learn something new every day, no? -- www.fsrtechnologies.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
"culpritNr1" wrote Say I have this nice list of lists: LoL = [['chrX', '160944034', '160944035', 'gnfX.145.788', '63.60'], ['chrX', '161109992', '161109993', 'rs13484104', '63.60'], Now I want to cast the second and third "columns" from string to integer, like this LoL = [['chrX', 160944034, 160944035, 'gnfX.145.788', '63.60'], ['chrX', 161109992, 161109993, 'rs13484104', '63.60'], Being picky that's not really casting that's converting. Casting is where you take the same set of binary data and treat it as if it were a different type but without changing the binary. Conversion is where you actually change the data into a new representation. Conversion is relatively easy in Python, casting is a bit more tricky. Alan G. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
>> except: >>pass >> >> try not to code these 2 lines in anything that you do because it will >> come back to haunt you when something is not working right but you >> can't find any errors. that's because this code masks and throws away >> everything!! > > there are two potential error types: IndexError and ValueError. I assumed > that if > either one occurred, we would want to leave that particular list member (if > it exists) as-is (hence the pass). >: > - catch the exception, test to see whether it's an IndexError or a > ValueError, and if not then do something; >: as opposed to the above... except (IndexError, ValueError): pass ...is much more acceptable. there are 2 general conventions: - catch errors explicitly (as to not mask the others) and pass/ignore - catch 'em all (except Exception) and do *some*thing (not pass) both of those cases shows that you did your due diligence and that you're just not blindly throwing things away. > Generally, if there are two or more "acceptable" errors that you can foresee, > but you still want to catch any others, what's an elegant, readable, and > computationally-cheap way to do it? Maybe a dictionary of exceptions...? A tuple of exceptions works, just like what we did above, and more, i.e., (IndexError, ValueError, TypeError, KeyError... hope this helps! -- wesley - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "Core Python Programming", Prentice Hall, (c)2007,2001 "Python Fundamentals", Prentice Hall, (c)2009 http://corepython.com wesley.j.chun :: wescpy-at-gmail.com python training and technical consulting cyberweb.consulting : silicon valley, ca http://cyberwebconsulting.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
On Thu, Jan 8, 2009 at 2:21 PM, wesley chun wrote: > except: >pass > > try not to code these 2 lines in anything that you do because it will > come back to haunt you when something is not working right but you > can't find any errors. that's because this code masks and throws away > everything!! > > if you are guaranteed that the strings all contain valid integers, > then you don't have to worry about problems calling int(). > OP said we couldn't be sure that all rows would have the same number of elements; I'm afraid I extrapolated that we also might not be sure they were all integers (or, I should say, strings representing integers...), so there are two potential error types: IndexError and ValueError. I assumed that if either one occurred, we would want to leave that particular list member (if it exists) as-is (hence the pass). I see three ways around this: - test each list for length, and each member for integer-ness, before casting anything; - catch the exception, test to see whether it's an IndexError or a ValueError, and if not then do something; - print/log every exception. The first one violates "It's better to ask forgiveness than to ask permission" (and it's slow), the second one's a pain in the butt; the third one gets slow if LoL is large and has many non-standard members. Is there a fourth way? Actually, I'm asking because I've run into similar situations and been dissatisfied with my own solution. Generally, if there are two or more "acceptable" errors that you can foresee, but you still want to catch any others, what's an elegant, readable, and computationally-cheap way to do it? Maybe a dictionary of exceptions...? -- www.fsrtechnologies.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
>> LoL = [['chrX', '160944034', '160944035', 'gnfX.145.788', '63.60'], >>: >> Now I want to cast the second and third "columns" from string to integer, >> like this >> >> LoL = [['chrX', 160944034, 160944035, 'gnfX.145.788', '63.60'], >>: >> Is there any elegant way to do this? I can't assume that all lines will >> have the same number of elements. the easiest way to do it is using int(), as in the below. > for lstA in LoL: > try: > lstA[1] = int(lstA[1]) > except: > pass > try: > lstA[2] = int(lstA[2]) > except: > pass it's definitely a *good* idea to check and make sure the numbers are legit, meaning that int() won't throw an exception, but it is a *bad* idea to have any code anywhere that looks like: except: pass try not to code these 2 lines in anything that you do because it will come back to haunt you when something is not working right but you can't find any errors. that's because this code masks and throws away everything!! if you are guaranteed that the strings all contain valid integers, then you don't have to worry about problems calling int(). hope this helps! -- wesley - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "Core Python Programming", Prentice Hall, (c)2007,2001 "Python Fundamentals", Prentice Hall, (c)2009 http://corepython.com wesley.j.chun :: wescpy-at-gmail.com python training and technical consulting cyberweb.consulting : silicon valley, ca http://cyberwebconsulting.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
Le Thu, 8 Jan 2009 11:51:01 -0800 (PST), culpritNr1 a écrit : > > Hi All, > > Say I have this nice list of lists: > > LoL = [['chrX', '160944034', '160944035', 'gnfX.145.788', '63.60'], > ['chrX', '161109992', '161109993', 'rs13484104', '63.60'], > ['chrX', '161414112', '161414113', 'rs13484105', '63.60'], > ['chrX', '161544071', '161544072', 'rs13484106', '63.60'], > ['chrX', '162030736', '162030737', 'gnfX.146.867', '67.05'], > ['chrX', '164171913', '164171914', 'gnfX.148.995', '70.45']] > > Now I want to cast the second and third "columns" from string to integer, > like this > > LoL = [['chrX', 160944034, 160944035, 'gnfX.145.788', '63.60'], > ['chrX', 161109992, 161109993, 'rs13484104', '63.60'], > ['chrX', 161414112, 161414113, 'rs13484105', '63.60'], > ['chrX', 161544071, 161544072, 'rs13484106', '63.60'], > ['chrX', 162030736, 162030737, 'gnfX.146.867', '67.05'], > ['chrX', 164171913, 164171914, 'gnfX.148.995', '70.45']] > > Is there any elegant way to do this? I can't assume that all lines will have > the same number of elements. In you do not need checking whether specific items are "castable" (i.e. you really know what's in the list) you may use such a pattern: lol = [[1,2,3],[4,5,6],[7,8,9]] new_lol = [[a,b**3,c] for [a,b,c] in lol] print lol print new_lol ==> [[1, 2, 3], [4, 5, 6], [7, 8, 9]] [[1, 8, 3], [4, 125, 6], [7, 512, 9]] denis > Thank you, > > Your Culprit > > -- la vida e estranya ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] casting string to integer in a list of lists
On Thu, Jan 8, 2009 at 11:51 AM, culpritNr1 wrote: > > Hi All, > > Say I have this nice list of lists: > > LoL = [['chrX', '160944034', '160944035', 'gnfX.145.788', '63.60'], > ['chrX', '161109992', '161109993', 'rs13484104', '63.60'], > ['chrX', '161414112', '161414113', 'rs13484105', '63.60'], > ['chrX', '161544071', '161544072', 'rs13484106', '63.60'], > ['chrX', '162030736', '162030737', 'gnfX.146.867', '67.05'], > ['chrX', '164171913', '164171914', 'gnfX.148.995', '70.45']] > > Now I want to cast the second and third "columns" from string to integer, > like this > > LoL = [['chrX', 160944034, 160944035, 'gnfX.145.788', '63.60'], > ['chrX', 161109992, 161109993, 'rs13484104', '63.60'], > ['chrX', 161414112, 161414113, 'rs13484105', '63.60'], > ['chrX', 161544071, 161544072, 'rs13484106', '63.60'], > ['chrX', 162030736, 162030737, 'gnfX.146.867', '67.05'], > ['chrX', 164171913, 164171914, 'gnfX.148.995', '70.45']] > > Is there any elegant way to do this? I can't assume that all lines will > have > the same number of elements. > Maybe not the most elegant way, but here's a quickie: print(LoL) for lstA in LoL: try: lstA[1] = int(lstA[1]) except: pass try: lstA[2] = int(lstA[2]) except: pass print(LoL) I put them in separate try/excepts in case the first one's not an integer but the second one is. -- www.fsrtechnologies.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
