"Hs Hs" <ilhs...@yahoo.com> wrote

I have a very large file 15Gb.

Every two lines are part of one readgroup.
I want to add two variables to every line.

HWUSI-EAS1211_0001:1:1:977:20764#0   RG:Z:2301
HWUSI-EAS1211_0001:1:1:977:20764#0    RG:Z:2302
...
Since I cannot read the entire file, I wanted to cat the file

What makes you think you cannot read the entire file?

something like this:

cat myfile  | python myscript.py > myfile.sam

How does that help over Python reading the file line by line?

I do not know how to execute my logic after I read the line, althought I tried:

while True:
       second = raw_input()
       x =  second.split('\t')

Why are you splitting theline? You only need to append
data to the end of the line...

Could someone help me here either what I want to do.

In pseudo code:

open input and ouput files
read the first 14 lines from input
oddLine = True
while True:
    read line from input
    if oddLine:
           append odd data
    else
          append evenData
    write line to output file
    oddLine = not oddLine

You probably want a try/except in there to catch the end of file.


This is not very different from the menu example in the file
handling topic of my tutorial...

HTH

--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/


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