arphaksad at gmail.com
Fri Aug 14 03:21:39 CEST 2009
On Aug 13, 7:50 am, Dave Angel <da... at ieee.org> wrote:
> naaman wrote:
> > On Aug 12, 1:35 pm, Dave Angel <da... at ieee.org> wrote:
> >> naaman wrote:
> >>> I'm writing my first Python script and
> >>> I want to use fileinput to open a file in r+ mode.
> >>> Tried fileinput.input(sys.argv[1:],"r+") but that didn't work.
> >>> ANy ideas?
> >>> Need to find and overwrite a line in a file several times.
> >>> I can do it using open and seek() etc. but was wondering if I can use
> >>> fileinput.
> >>> thanks;
> >> I haven't used it, but check out the 'inplace' keyword parameter.
> >> DaveA
> > I've only Python for a week so I'm not sure what inplace does
> You should read the docs for it
> (http://www.python.org/doc/2.6.2/library/fileinput.html ),
> but it's not very clear to me either So I dug up an example on the web:
> (ref: http://effbot.org/librarybook/fileinput.htm)
> import fileinput, sys
> for line in fileinput.input(inplace=1):
> # /convert Windows/DOS text files to Unix files/
> if line[-2:] == "\r\n":
> line = line[:-2] + "\n"
> The inplace argument tells it to create a new file with the same name as
> the original (doing all the necessary nonsense with using a scratch
> file, and renaming/deleting) for each file processed. Stdout is pointed
> to that new version of the file. Notice that you have to explicitly
> write everything you want to wind up in the file -- if a given line is
> to remain unchanged, you just write "line" directly.
> If you're new to Python, I do not recommend trying to do open/seek to
> update a text file in place, especially if you're in DOS. There are
> lots of traps. the inplace method of fileinput avoids these by
> implicitly creating temp files and handling the details for you, which
> probably works great if you're dealing with text, in order.
Thanks Dave. I'll check that out
More information about the Python-list