On May 16, 5:57 pm, castironpi <[EMAIL PROTECTED]> wrote: > On May 16, 5:22 pm, castironpi <[EMAIL PROTECTED]> wrote: > > > > > > > On May 16, 2:25 pm, 7stud <[EMAIL PROTECTED]> wrote: > > > > globalrev wrote: > > > > i ahve a program that takes certain textsnippets out of one file and > > > > inserts them into another. > > > > > problem is it jsut overwrites the first riow every time. > > > > > i want to insert every new piece of text into the next row. > > > > so: > > > > 1. how do i write to a new line every time i write to the file? > > > > > 2. if i dont want to write to a new line but just want to insert it > > > > after the last token in the file, how do i do then? > > > > Generally, you can't "insert" anything into a file. You can either > > > append to the end of a file, or you can rewrite the whole file. It > > > sounds like you probably want to read the file into an array using > > > readlines(). Then manipulate that array however you want--appending > > > and inserting--and when you are done, overwrite the file with your > > > array. > > > > However, you should be aware that as soon as you open a file for > > > writing all the data is erased, and if your program should happen to > > > crash right then, the array containing the data will disappear into > > > the ether and your file will be empty--in other words all your data > > > will be gone. To prevent such an occurence, you should write your > > > final data to another file, then delete the original file, and finally > > > change the other file's name to the original file name. > > > Some options: > > > 1. Limit line length. Then offset is ( line* length ). > > 2. Name your relation. > > 3. Hijack the operating system. Remember: > > > abc > > def > > > on disk looks like > > abc\ndef > > > where > > > abcd > > def > > > looks like > > abcd\ndef > > > So, if you want line 2, you have to scan line 1.- Hide quoted text - > > > - Show quoted text - > > You also have > > f.seek( X ) > f.write( 'abc' ) > > which writes 'abc' in the middle, at offset X. > > f.seek( 0, SEEK_END ) > > takes you to the back, and don't forget > > f.flush( ). > > Say you have: > > File: > > abc > def > ghi > > Symbols: > > 0-3 > 1-3 > 2-3 > > abcdefghi > > and you want to make abc abC. Then > > f.seek( 2 ) > f.write( 'C' ) > > does work. > > If you want to make abc ab, then you change a different file > > table.seek( 0 ) > table.write( chr( 2 ) ) > > ( or bytes( [ 2 ] ) in 3.0 ). > > If you want to make abc abcd, then you change both. > > f.seek( 9 ) > f.write( 'd' ) > > table.seek( 0 ) > table.write( chr( 4 ) ) > > But. Now you have item 0 in two places. 'abc' somewhere and 'd' > somewhere else, at 0 and at 9 respectively. I think the file system > overallocates room for String 1. You would read: > > 0- 2- [ 3, 1 ] > > for 'abc'+'d' > > and > > 1- 1- [ 3 ] > 2- 1- [ 3 ] > > for 'def' and 'ghi', where actual representations would be: > > 0- 2- [ 0/3, 9/1, 0, 0, 0, 0, 0, 0 ] > 1- 1- [ 3/3, 0, 0, 0, 0, 0, 0, 0 ] > 2- 1- [ 6/3, 0, 0, 0, 0, 0, 0, 0 ] > > As your chains start to grow, leave table 8xN, and just copy strings > to new sectors when they become long: > > 0- 1- [ 9/4, 0, 0, 0, 0, 0, 0, 0 ] > 1- 1- [ 3/3, 0, 0, 0, 0, 0, 0, 0 ] > 2- 1- [ 6/3, 0, 0, 0, 0, 0, 0, 0 ] > > You can insort in linear time when you're looking for available slots. > > 'jklm' can't fit at 0. > > 0- 1- [ 9/4, 0, 0, 0, 0, 0, 0, 0 ] > 1- 1- [ 3/3, 0, 0, 0, 0, 0, 0, 0 ] > 2- 1- [ 6/3, 0, 0, 0, 0, 0, 0, 0 ] > 3- 1- [ 13/4, 0, 0, 0, 0, 0, 0, 0 ] > > but 'nop' can. > > 0- 1- [ 9/4, 0, 0, 0, 0, 0, 0, 0 ] > 1- 1- [ 3/3, 0, 0, 0, 0, 0, 0, 0 ] > 2- 1- [ 6/3, 0, 0, 0, 0, 0, 0, 0 ] > 3- 1- [ 13/4, 0, 0, 0, 0, 0, 0, 0 ] > 4- 1- [ 0/3, 0, 0, 0, 0, 0, 0, 0 ] > > 'jklm' could've with a split: > > 0- 1- [ 9/4, 0, 0, 0, 0, 0, 0, 0 ] > 1- 1- [ 3/3, 0, 0, 0, 0, 0, 0, 0 ] > 2- 1- [ 6/3, 0, 0, 0, 0, 0, 0, 0 ] > 3- 2- [ 0/3, 13/1, 0, 0, 0, 0, 0, 0 ] > > and with 'nop': > > 0- 1- [ 9/4, 0, 0, 0, 0, 0, 0, 0 ] > 1- 1- [ 3/3, 0, 0, 0, 0, 0, 0, 0 ] > 2- 1- [ 6/3, 0, 0, 0, 0, 0, 0, 0 ] > 3- 2- [ 0/3, 13/1, 0, 0, 0, 0, 0, 0 ] > 4- 1- [ 14/3, 0, 0, 0, 0, 0, 0, 0 ] > > There's an easy chance you can beat DbfilenameShelf for your > application.- Hide quoted text - > > - Show quoted text -
I am still interested in this one, but doubt if anyone still reading. -- http://mail.python.org/mailman/listinfo/python-list
