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Re: Python path and append

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Random832 wrote:

> On Mon, Apr 25, 2016, at 16:15, Seymore4Head wrote:
>> Thanks for the tip.
>> 
>> Still broke.  :(
>> 
>> f = open('wout.txt', 'r+')
>> for line in f:
>>     if line=="":
>>         exit
>>     line=line[:-1]
>>     line=line+" *"
>>     f.write(line)
>>     print line
>> f.close()
> 
> Your problem is that after you read the first line, your file "cursor"
> is positioned after the end of that line. So when you write the modified
> version of the line, it ends up after that. And then when you write it,
> the cursor is wherever the end of that is.
> 
> So if you start with this:
> AAA
> BBB
> CCC
> 
> You'll end up with this:
> AAA
> AAA* [this overwrites "BBB_C" with "AAA*_" if _ is the line break]
> CC
> CC*
> 
> There's no good way around this. You can either read the whole file into
> memory at once into a list, then rewind (look at the seek function) and
> write the lines out of the list, or you can write to a *different* file
> than the one you're reading.

You can leave the details to python though:

$ cat sample.txt
alpha
beta
gamma
$ python
Python 2.7.6 (default, Jun 22 2015, 17:58:13) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import fileinput
>>> for line in fileinput.input("sample.txt", inplace=True):
...     print line.rstrip("\n"), "*"
... 
>>> 
$ cat sample.txt 
alpha *
beta *
gamma *

Too much magic for my taste, but the OP might like it.

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Python path and append Seymore4Head <Seymore4Head@Hotmail.invalid> - 2016-04-19 18:29 -0400
  Re: Python path and append Chris Angelico <rosuav@gmail.com> - 2016-04-20 08:38 +1000
  Re: Python path and append Matthew Barnett <mrabarnett@mrabarnett.plus.com> - 2016-04-20 00:36 +0100
  Re: Python path and append Seymore4Head <Seymore4Head@Hotmail.invalid> - 2016-04-25 14:10 -0400
    Re: Python path and append Rob Gaddi <rgaddi@highlandtechnology.invalid> - 2016-04-25 18:24 +0000
      Re: Python path and append Seymore4Head <Seymore4Head@Hotmail.invalid> - 2016-04-25 15:00 -0400
        RE: Python path and append Joaquin Alzola <Joaquin.Alzola@lebara.com> - 2016-04-25 19:08 +0000
          Re: Python path and append Seymore4Head <Seymore4Head@Hotmail.invalid> - 2016-04-25 16:15 -0400
            Re: Python path and append Random832 <random832@fastmail.com> - 2016-04-25 16:28 -0400
            Re: Python path and append Peter Otten <__peter__@web.de> - 2016-04-25 23:38 +0200
            Re: Python path and append Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2016-04-25 19:57 -0400
        Re: Python path and append Rob Gaddi <rgaddi@highlandtechnology.invalid> - 2016-04-25 19:31 +0000
        Re: Python path and append MRAB <python@mrabarnett.plus.com> - 2016-04-25 20:44 +0100
          Re: Python path and append Seymore4Head <Seymore4Head@Hotmail.invalid> - 2016-04-25 16:43 -0400
        Re: Python path and append Steven D'Aprano <steve@pearwood.info> - 2016-04-26 11:51 +1000
          Re: Python path and append Dan Sommers <dan@tombstonezero.net> - 2016-04-26 01:59 +0000
          Re: Python path and append Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-04-26 18:23 +1200
          Re: Python path and append boB Stepp <robertvstepp@gmail.com> - 2016-04-29 15:26 -0500
            Re: Python path and append Steven D'Aprano <steve@pearwood.info> - 2016-04-30 11:44 +1000
    Re: Python path and append John Gordon <gordon@panix.com> - 2016-04-25 21:26 +0000
      Re: Python path and append Seymore4Head <Seymore4Head@Hotmail.invalid> - 2016-04-25 18:04 -0400
        Re: Python path and append Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2016-04-25 20:03 -0400
        Re: Python path and append Steven D'Aprano <steve@pearwood.info> - 2016-04-26 11:53 +1000
          Re: Python path and append Seymore4Head <Seymore4Head@Hotmail.invalid> - 2016-04-26 22:56 -0400
            Re: Python path and append Chris Angelico <rosuav@gmail.com> - 2016-04-27 13:06 +1000
            Re: Python path and append Stephen Hansen <me+python@ixokai.io> - 2016-04-27 17:24 -0700
      Re: Python path and append Chris Angelico <rosuav@gmail.com> - 2016-04-26 10:25 +1000

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