On Tue, Aug 11, 2009 at 4:52 PM, Helvin<helvin...@gmail.com> wrote: > Hi everyone, > > I am writing some python script that should find a line which contains > '1' in the data.txt file, then be able to move a certain number of > lines down, before replacing a line. At the moment, I am able to find > the line '1', but when I use f.seek to move, and then rewrite, what I > write goes to the end of the .txt file, instead of being adjusted by > my f.seek. > > Do you know what way I should take? >
It might be easier to read the file into a list of lines (using readlines, as you do in your code already), make your change there and write it back to a file. If your file is indeed as small as you indicate below, that should be significantly easier. > Data.txt is a file of 3 lines: > line1 > line2 > line3 > > Code: > > with open('data.txt', 'r+') as f: > firstread = f.readlines() # Take a snapshot of initial file > > f.seek(0,0) # Go back to beginning and search > for line in f: > print line > if line.find('1'): > print 'line matched' > f.seek(1,1) # Move one space along > f.write('house\n') # f.write overwrites the exact > number of bytes. > break # leave loop once '1' is found > > f.seek(0,0) # Go back to beginning, and read > data.txt again > lastread = f.readlines() > > print 'firstread is', firstread > print 'lastread is', lastread > > This shouldn't be too difficult, but I don't know how. > < > Help appreciated! -- http://mail.python.org/mailman/listinfo/python-list