Cat,grep and redirect to python

Question

cat filename | grep "something" >> file2.txt

with open("filename") as origin_file:
    for line in origin_file:
        line = re.findall(r"something",line)

    f=open('file2.txt','w')
    subprocess.call('line',stdout=f)    
    f.close()

This is what I've tried...Doesn't work.

Answer 1

Simplest solution I can think of:

with open('filename', 'r') as in_f, open('file2.txt', 'a') as out_f:
    for line in in_f:
        if 'something' in line:
            out_f.write(line)