find, replace and save string in ascii file

[Andy Terrel]

Take your code, pretend it is in file:

 $------------------------
NAME='ALFA'
CODE='x'
$------------------------


a python functions could be:

def change(filename):
    fp = open(filename, 'r')
    lines = fp.readlines()
    fp.close()
    for i in range(len(lines)):
        if lines[i].find('NAME') >= 0:
          if lines[i+1].find('CODE') >= 0:
              code = lines[i+1].split('=')[1]
              lines[i] = 'NAME='+<something based off code>
     fp2 = open(filename,'w')
     fp2.write("".join(lines))



So this is pretty crude and not very robust.  But should give you about
some idea of how to write something.  I'm not sure if there is a way
around opening two file pointers but  I think python has no problems
with this.  Also if you files can't fit into memory you probably want
to do something a lot more, that is read only a block at a time and
then mess with stuff, probably writing out to a temp file and then
overwriting your original file.


peter wrote:
> Thank you for your advice.
>
> I'm not so good in python yet, so could you be so kind and write me a
> piece of code for the part
>
>  If you want the output to be written to same file just 'move' this
>  temperory file to the input file once you are done.
>
> Because that's what I don't know how to do it. How to replace a string
> in the middle of the file and than save this file.
>
> Thanks a lot.
>
>
> Amit Khemka wrote:
> > On 23 Aug 2006 05:48:37 -0700, peter <borique at gmail.com> wrote:
> > > Hello all,
> > >
> > > I'm looking for an advice.
> > >
> > > Example (one block in ascii file):
> > > $------------------------
> > > NAME='ALFA'
> > > CODE='x'
> > > $------------------------
> > >
> > > There are many similar blocks in the file with different NAMEs and
> > > different CODEs. What I'm looking for is a script that searchs through
> > > whole file and finds all strings with name ALFA and based on what CODE
> > > is after each ALFA (can be x, y or z) the ALFA name is replaced by
> > > BETAx,BETAy or BETAz and so changed file saves.
> > >
> > > What I did is that I can find all strings which I need, next I change
> > > these strings based on CODE, but what I can't is to replace old string
> > > with new one, on the same position in the file. It always writes new
> > > string at the end of the file. Here is my code....
> >
> > A simpler way can be:
> >
> > 1. Read a 'block' from the input file, ( you can simply read a line
> > starting with 'NAME' and keep on reading till you find a line with
> > starting 'CODE')
> > 2. Once you have read a 'block', make whatever you want changes to the
> > NAME and then write the 'block' to a temperory file.
> >
> > If you want the output to be written to same file just 'move' this
> > temperory file to the input file once you are done.
> >
> > Note: if there is other stuff in the input file, apart from such
> > 'blocks' that you want to preserve, a small modification in step 1
> > would take care of it.
> >
> > hth,
> > amit.
> >
> > --
> > ----
> > Amit Khemka -- onyomo.com
> > Home Page: www.cse.iitd.ernet.in/~csd00377
> > Endless the world's turn, endless the sun's Spinning, Endless the quest;
> > I turn again, back to my own beginning, And here, find rest.