noob trying to write a simple python script, help please =]

[Disco Boy]

Hello all,

I am trying to write a python script which takes an input file and multiplies some numbers before outputting.

Here's the start of the file:

# This file was created Wed Nov  2 12:37:30 2011
# by the following command:
# g_dist -f md1_10.xtc -s run1.tpr -n index.ndx -o triad_thr136_asn86_dist_ox1M_1.xvg 
#
# g_dist is part of G R O M A C S:
#
# GRoups of Organic Molecules in ACtion for Science
#
@    title "Distance"
@    xaxis  label "Time (ps)"
@    yaxis  label "Distance (nm)"
@TYPE xy
@ view 0.15, 0.15, 0.75, 0.85
@ legend on
@ legend box on
@ legend loctype view
@ legend 0.78, 0.8
@ legend length 2
@ s0 legend "|d|"
@ s1 legend "d\sx\N"
@ s2 legend "d\sy\N"
@ s3 legend "d\sz\N"
   0.0000000    0.7551542   -0.6089997    0.2760000    0.3510003
  20.0000000    0.7571034   -0.5939999    0.2770000    0.3789997
  40.0000000    0.6894182   -0.5540004    0.2700000    0.3090000
  60.0000000    0.6623963   -0.5409999    0.2579999    0.2820001
  80.0000000    0.6986261   -0.5410004    0.3189998    0.3060002
 100.0000000    0.6851938   -0.5509996    0.3109999    0.2630000

n.b. the first column goes up to 50,000.

Specifically, I want it to print the first few header lines (# and @ at the start). Then, for every row, to divide the value in the first column by 1000, and multiply the value in the second column by 10 (i.e. it's converting the units). The 3rd, 4th and 5th columns I am not interested in.

Here's what I have got so far:

import sys
import re

inp1 = sys.argv[1]
file = open(inp1, "r")
n = 1000.0000000
x = 10.0000000

lines = open( sys.argv[1], "r" ).readlines()

for line in file:
    if re.search( r"#", line ):   ## print header ##
        print line,
    if re.search( r"@", line ):   # print header ##
        print line,
    else:
        for i in range( 1, len(lines) ):
            line = lines[i].rstrip()
            words = line.split("    ")
            a = words[0] / n
            b = words[1] * x
            print "%f %f" % (a, b)

You'll see when you run it that it has a problem with strings and floats...

Can anyone with a clue give me a hand at all?

Thank you

 

[Disco Boy]

Thanks for your help Jack.

I actually started to have a go at doing it in perl and have managed to achieve it

here it is in all of its glory

$filename = $ARGV[0];
$x = 1000;
$y = 10;


open FILE,"<$filename" or die "Cannot read from $filename: $!\n";


$filename = $ARGV[0];
    
open FILE,"<$filename" or die "Cannot read the file $filename: $!\n";

while ($line = <FILE>)
{
    if ($line =~ m/@/)
    {
        print $line;
    }
    elsif ($line =~ m/#/)
    {
        print $line;
    }

    else 
    {
        chomp $line;

        @words = split("   ",$line);
        $col1 = $words[0] / $x;
        $col2 = $words[1] * $y;

    print "$col1  $col2\n";
    }


}