Slicing Output Files

I'm reading in a large file and I want to write a certain portion of it to a new file.

The pattern 'CARTESIAN COORDINATES' appears twice in this file and I want to omit everything before the second occurrence in the new file. So far I have:

#!/usr/bin/env python
import string,sys
import numpy as np
from numpy import *

with open("101.out", "r") as f:
    content = []
    for line in f:
        content.append(line)

g = open('101.xyz', 'w')


#write the relevant stuff


f.close()

Solution

So I'm assuming the 101.out file looks something like:

not to be written 
not to be written
CARTESIAN COORDINATES
not to be written
CARTESIAN COORDINATES
written 
written
written

And you want all the stuff after the second CARTESIAN COORDINATES if I've understood you correctly:

#!/usr/bin/env python
import string,sys
import numpy as np
from numpy import *

with open("101.out", "r") as f:
    content = []
    occurances = 0
    for line in f:
        if occurances >= 2: 
            content.append(line)
        if 'CARTESIAN COORDINATES' in line:
            occurances += 1

with open('101.xyz', 'w') as f:
    for item in content:
        f.write(item)

None of those imports are required for the work, I've just left them there because they were in your original snippet.

This outputs to 101.xyz:

written
written
written