Re: [Tutor] Accessing next and previous items during iteration
On 18/12/05, Kent Johnson [EMAIL PROTECTED] wrote: Ed Singleton wrote: Is it possible to access the next and previous items during an iteration? This just came up on c.l.python. Bengt Richter has a nice generator-based solution. http://groups.google.com/group/comp.lang.python/browse_thread/thread/2e4533f108fbf172/90d87c91dac844d3?hl=en#90d87c91dac844d3 That's perfect! It's a lovely piece of code as well. Obvious once you've seen it, but you wouldn't have thought of it before hand. Thanks Ed ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Accessing next and previous items during iteration
Ed Singleton wrote: Is it possible to access the next and previous items during an iteration? This just came up on c.l.python. Bengt Richter has a nice generator-based solution. http://groups.google.com/group/comp.lang.python/browse_thread/thread/2e4533f108fbf172/90d87c91dac844d3?hl=en#90d87c91dac844d3 Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Accessing next and previous items during iteration
Ed Singleton wrote: Is it possible to access the next and previous items during an iteration? There is nothing built in to support this directly. I'm currently using: prev = 0 current = 0 next = 0 for page in folder: prev = current current = next next = page if current: if prev: #add link to previous page #add link to next page if current: if prev: #add link to previous page #add link to next page I think there is a bug here - when the loop exits, prev, current and next will all be valid with next containing the last page. You have already added the links to current, it is next that needs a link to the previous page. But this seems a really awkward way to do it. I've considered iterating and dumping them all into a list and then iterating through the list, but that also seems awkward (having to iterate twice). You don't say what kind of object folder is. If it is a directory listing e.g. from os.listdir() then it is already a list. In any case you should be able to make a list without an explicit iteration using pages = list(folder) Is there a nice way to do it? How about this: pages = list(folder) # make sure we have a list for i, page in enumerate(pages): if i 0: previous = pages[i-1] # add link to previous if i+1 len(pages): next = pages[i+1] # add link to next Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Accessing next and previous items during iteration
| Is it possible to access the next and previous items during an | iteration? | | I want to use it to iterate through html files in a folder and add | links in to the next and previous pages. | I just did this :-) What I did was 1) use the glob module to get a list of the files in the directory (*.htm) 2) sort this using a special sort function (in my case the files were named as #_# where # was a number and I wanted to sort according to the first number and subsort according to the second) 3) then I just stepped through the list using enumerate and used the index to find the next and previous names in the list, e.g. for i, fil in enumerate(flist): if i1: prev = flist[i-1] #do previous link if i len(flist): next = flist[i+1] #do next link /c ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Accessing next and previous items during iteration
| Is it possible to access the next and previous items during an | iteration? | | I want to use it to iterate through html files in a folder and add | links in to the next and previous pages. | I just did this :-) What I did was 1) use the glob module to get a list of the files in the directory (*.htm) 2) sort this using a special sort function (in my case the files were named as #_# where # was a number and I wanted to sort according to the first number and subsort according to the second) 3) then I just stepped through the list using enumerate and used the index to find the next and previous names in the list, e.g. for i, fil in enumerate(flist): if i1: prev = flist[i-1] #do previous link if i len(flist): next = flist[i+1] #do next link /c ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Accessing next and previous items during iteration
| Is it possible to access the next and previous items during an | iteration? | | I want to use it to iterate through html files in a folder and add | links in to the next and previous pages. | I just did this :-) What I did was 1) use the glob module to get a list of the files in the directory (*.htm) 2) sort this using a special sort function (in my case the files were named as #_# where # was a number and I wanted to sort according to the first number and subsort according to the second) 3) then I just stepped through the list using enumerate and used the index to find the next and previous names in the list, e.g. for i, fil in enumerate(flist): if i1: prev = flist[i-1] #do previous link if i len(flist): next = flist[i+1] #do next link /c ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Accessing next and previous items during iteration
Chris or Leslie Smith wrote: I just did this :-) What I did was 1) use the glob module to get a list of the files in the directory (*.htm) 2) sort this using a special sort function (in my case the files were named as #_# where # was a number and I wanted to sort according to the first number and subsort according to the second) 3) then I just stepped through the list using enumerate and used the index to find the next and previous names in the list, e.g. You have a couple of errors in your conditionals for i, fil in enumerate(flist): if i1: prev = flist[i-1] This should be 'if i = 1'. If i==0 your condition will be true and you will set prev = flist[-1] which is the *last* item in flist. #do previous link if i len(flist): next = flist[i+1] should be 'if i+1 len(flist)' to avoid an IndexError on the last element. Kent #do next link /c ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
