<[EMAIL PROTECTED]> wrote: > hi > > i have a file something like this > > abcdefgh > ijklmnopq > 12345678 > rstuvwxyz > ..... > ..... > ..... > 12345678 > ..... > > whenever i search the file and reach 12345678, how do i get the line > just above and below ( or more than 1 line above/below) the pattern > 12345678 and save to variables? thanks
If the file's of reasonable size, read it all into memory into a list of lines with a .readlines method call, then loop with an index over said list and when you find your pattern at index i use i-1, i+1, and so on (just check that the resulting i+N or i-N is >=0 and <len(thelist)). If the file's too big to keep in memory at once, you need more clever approaches -- keep a collections.deque of the last M lines read to be able to get "N lines ago" for N<M, and for getting lines "after" the one of interest (which you will read only in "future" iterations) keep track of relative linenumbers that "will" interest you, decrement them with each line read, trigger when they reach 0. But unless you're dealing with files of many, MANY hundres of megabytes, on any typical modern machine you should be OK with the first, WAY simpler approach. Alex -- http://mail.python.org/mailman/listinfo/python-list
