How to break a file into two and then search only through the second half?

Question

How does one break a file into two parts depending on a key word...and then parse through that file for the expression 'chain "edt_'?

Answer 1

Here is an example text file (named temp.txt):

hello 10 20 30
goodbye 20 30 40
keyword 5 6 7
chain "edt_ 0 1 2
rubbish 2 3 4
more 6 7 8
test 1 2 3

If we want to split the file when we find keyword, and then search for the expression chain "edt_, this is one way to do it:

# Read the file
with open('temp.txt','r') as f:
    data = f.readlines()

# Strip out newline char
data = [i.strip('\n') for i in data]

# Look for keyword
kwLoc = [i.find('keyword') for i in data].index(0)

print 'Keyword found on line {0} - splitting file.'.format(kwLoc)

# Split the file
partOne = data[:kwLoc]
partTwo = data[kwLoc:]

# Optionally save each file
with open('temp_1.txt','w') as f:
    for row in partOne:
        f.writelines(row)
        f.write('\n')

with open('temp_2.txt','w') as f:
    for row in partTwo:
        f.writelines(row)
        f.write('\n')

# Now search the file for the expression - returning the row where it occurs

exLoc = [i.find('chain "edt_')>0 for i in partTwo].index(True)


print 'Found expression chain "edt on row {0}.'.format(exLoc)

Is this what you wanted to do?