[Tutor] Truncate First Line of File

[Bill Campbell]

On Wed, Feb 27, 2008, Alex Ezell wrote:
>I must be missing some simple method on a file object or something.
>
>What I need to do is to truncate the first line of a file which has an
>unknown number of lines and an unknown size.
>
>The only thing I can think to do is to readlines() and then slice off
>the first line in the resulting list, then writelines().
>
>pseduo-code:
>my_file = open('file.txt', 'wb')
>lines = my_file.readlines()
>del lines[0]
>my_file.writelines()
>my_file.close()
>
>Is there a better way?

Defensive programming avoids slurping entire files of unknown
size into memory.  I would just open the file, use readline() to
get rid of the first line, the loop writing the rest.

If you're going to slurp the whole thing:

infile = open('inputfile')
lines = infile.readlines()
outfile = open('outfile', 'wb')
outfile.writelines(lines[1:])
outfile.close()

Another way on *nix systems that might be better wouldn't use
python at all.  Edit the file in place with ed or ex:

#!/bin/sh
ex - filename <<DONE
1d
w
q
DONE

Bill
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